CHAPTER I

HYMENOPTERA PETIOLATA _CONTINUED_

SERIES 2. TUBULIFERA OR CHRYSIDIDAE—SERIES 3. ACULEATA—GENERAL— CLASSIFICATION—DIVISION I. ANTHOPHILA OR BEES

The First Series—Parasitica—of the Sub-Order Hymenoptera Petiolata was discussed in the previous volume. We now pass to the Second Series.

SERIES 2. HYMENOPTERA TUBULIFERA.

_Trochanters undivided; the hind-body consisting of from three to five visible segments; the female with an ovipositor, usually retracted, transversely segmented, enveloping a fine, pointed style. The larvae usually live in the cells of other Hymenoptera._

The Tubulifera form but a small group in comparison with Parasitica and Aculeata, the other two Series of the Sub-Order. Though of parasitic habits, they do not appear to be closely allied to any of the families of Hymenoptera Parasitica, though M. du Buysson suggests that they have some affinity with Proctotrypidae; their morphology and classification have been, however, but little discussed, and have not been the subject of any profound investigation. At present it is only necessary to recognise one family, viz. Chrysididae or Ruby-wasps.[1] These Insects are usually of glowing, metallic colours, with a very hard, coarsely-sculptured integument. Their antennae are abruptly elbowed, the joints not being numerous, usually about thirteen, and frequently so {2}connected that it is not easy to count them. The abdomen is, in the great majority, of very peculiar construction, and allows the Insect to curl it completely under the anterior parts, so as to roll up into a little ball; the dorsal plates are very strongly arched, and seen from beneath form a free edge, while the ventral plates are of less hard consistence, and are connected with the dorsal plates at some distance from the free edge, so that the abdomen appears concave beneath. In the anomalous genus _Cleptes_ the abdomen is, however, similar in form to that of the Aculeate Hymenoptera, and has four or five visible segments, instead of the three or four that are all that can be seen in the normal Chrysididae. The larvae of the Ruby-flies have the same number of segments as other Hymenoptera Petiolata. The difference in this respect of the perfect Chrysididae from other Petiolata is due to a greater number of the terminal segments being indrawn so as to form the tube, or telescope-like structure from which the series obtains its name. This tube is shown partially extruded in Fig. 1; when fully thrust out it is seen to be segmented, and three or four segments may be distinguished. The ovipositor proper is concealed within this tube; it appears to be of the nature of an imperfect sting; there being a very sharply pointed style, and a pair of enveloping sheaths; the style really consists of a trough-like plate and two fine rods or spiculae. There are no poison glands, except in _Cleptes_, which form appears to come very near to the Aculeate series. Some of the Chrysididae on occasions use the ovipositor as a sting, though it is only capable of inflicting a very minute and almost innocuous wound.

[Illustration: Fig. 1.—_Chrysis ignita_, ♀. England.]

Although none of the Ruby-flies attain a large size, they are usually very conspicuous on account of their gaudy or brilliant colours. They are amongst the most restless and rapid of Insects; {3}they love the hot sunshine, and are difficult of capture. Though not anywhere numerous in species, they are found in most parts of the world. In Britain we have about twenty species. They usually frequent old wood or masonry, in which the nests of Aculeate Hymenoptera exist, or fly rapidly to and fro about the banks of earth where bees nest. Dr. Chapman has observed the habits of some of our British species.[2] He noticed _Chrysis ignita_ flying about the cell of _Odynerus parietum_, a solitary wasp that provisions its nest with caterpillars; in this cell the _Chrysis_ deposited an egg, and in less than an hour the wasp had sealed the cell. Two days afterwards this was opened and was found to contain a larva of _Chrysis_ a quarter of an inch long, as well as the Lepidopterous larvae stored up by the wasp, but there was no trace of egg or young of the wasp. Six days after the egg was laid the _Chrysis_ had eaten all the food and was full-grown, having moulted three or four times. Afterwards it formed a cocoon in which to complete its metamorphosis. It is, however, more usual for the species of _Chrysis_ to live on the larva of the wasp and not on the food; indeed, it has recently been positively stated that _Chrysis_ never eats the food in the wasp's cell, but there is no ground whatever for rejecting the evidence of so careful an observer as Dr. Chapman. According to M. du Buysson the larva of _Chrysis_ will not eat the lepidopterous larvae, but will die in their midst if the _Odynerus_ larva does not develop; but this observation probably relates only to such species as habitually live on _Odynerus_ itself. The mother-wasp of _Chrysis bidentata_ searches for a cell of _Odynerus spinipes_ that has not been properly closed, and that contains a full-grown larva of that wasp enclosed in its cocoon. Having succeeded in its search the _Chrysis_ deposits several eggs—from six to ten; for some reason that is not apparent all but one of these eggs fail to produce young; in two or three days this one hatches, the others shrivelling up. The young _Chrysis_ larva seizes with its mouth a fold of the skin of the helpless larva of the _Odynerus_, and sucks it without inflicting any visible wound. In about eleven days the _Chrysis_ has changed its skin four times, has consumed all the larva and is full-fed; it spins its own cocoon inside that of its victim, and remains therein till the following spring, when it changes to a pupa, and in less than three weeks {4}thereafter emerges a perfect _Chrysis_ of the most brilliant colour, and if it be a female indefatigable in activity. It is remarkable that the larva of _Chrysis_ is so much like that of _Odynerus_ that the two can only be distinguished externally by the colour, the _Odynerus_ being yellow and the _Chrysis_ white; but this is only one of the many cases in which host and parasite are extremely similar to the eye. _Chrysis shanghaiensis_ has been reared from the cocoons of a Lepidopterous Insect—_Monema flavescens_, family Limacodidae—and it has been presumed that it eats the larva therein contained. All other Chrysids, so far as known, live at the expense of Hymenoptera (usually, as we have seen, actually consuming their bodies), and it is not impossible that _C. shanghaiensis_ really lives on a Hymenopterous parasite in the cocoon of the Lepidopteron.

_Parnopes carnea_ frequents the nests of _Bembex rostrata_, a solitary wasp that has the unusual habit of bringing from time to time a supply of food to its young larva; for this purpose it has to open the nest in which its young is enclosed, and the _Parnopes_ takes advantage of this habit by entering the cell and depositing there an egg which produces a larva that devours that of the _Bembex_. The species of the anomalous genus _Cleptes_ live, it is believed, at the expense of Tenthredinidae, and in all probability oviposit in their cocoons which are placed in the earth.

SERIES 3. HYMENOPTERA ACULEATA.

_The females (whether workers or true females) provided with a sting: trochanters usually undivided (monotrochous). Usually the antennae of the males with thirteen, of the females with twelve, joints (exceptions in ants numerous)._

These characters only define this series in a very unsatisfactory manner, as no means of distinguishing the "sting" from the homologous structures found in Tubulifera, and in the Proctotrypid division of Hymenoptera Parasitica, have been pointed out. As the structure of the trochanters is subject to numerous exceptions, the classification at present existing is an arbitrary one. It would probably be more satisfactory to separate the Proctotrypidae (or a considerable part thereof) from the Parasitica, and unite them with the Tubulifera and Aculeata in a great series, characterised by the fact that the ovipositor is {5}withdrawn into the body in a direct manner so as to be entirely internal, whereas in the Parasitica it is not withdrawn in this manner, but remains truly an external organ, though in numerous cases concealed by a process of torsion of the terminal segments. If this were done it might be found possible to divide the great group thus formed into two divisions characterised by the fact that the ovipositor in one retains its function, the egg passing through it (Proctotrypidae and Tubulifera), while in the other the organ in question serves as a weapon of offence and defence, and does not act as a true ovipositor, the egg escaping at its base. It would, however, be premature to adopt so revolutionary a course until the comparative anatomy of the organs concerned shall have received a much greater share of attention; a detailed scrutiny of Prototrypidae being particularly desired.

[Illustration: Fig. 2.—Diagram of upper surface of _Priocnemis affinis_ ♀, Pompilidae. _o_, ocelli; _B^1_, pronotum; _B^2_, mesonotum; _B^3_, scutellum of mesonotum; _B^4_, post-scutellum or middle part of metanotum; _B^5_, propodeum or median segment (see vol. v. p. 491); _B^6_, combing hairs, pecten, of front foot: _C^1_, first segment of abdomen, here not forming a pedicel or stalk: _D^1_, coxa; _D^2_, trochanter; _D^3_, femur; _D^6_, calcaria or spurs of hind leg: 1 to 15, nervures of wings, viz. 1, costal; 2, post-costal; 3, median; 4, posterior; 5, stigma; 6, marginal; 7, upper basal; 8, lower basal; 9, 9, cubital; 10, the three sub-marginal; 11, first recurrent; 12, second recurrent; 13, anterior of hind wing; 14, median; 15, posterior: I to XI, the cells, viz. I, upper basal; II, lower basal; III, marginal; IV, V, VI, first, second and third sub-marginal; VII, first discoidal; VIII, third discoidal; IX, second discoidal; X, first apical; XI, second apical.]

We have dealt with the external anatomy of Hymenoptera in {6}Vol. V.; so that here it is only necessary to give a diagram to explain the terms used in the descriptions of the families and sub-families of Aculeata, and to discuss briefly their characteristic structures.

[Illustration: Fig. 3—Sting of bee. A, One of the needles separated; _a_, the barbed point; _b_, piston; _c_, arm. B, Transverse section of the sting: _dd_, the two needles; _e_, bead for guiding the needles; _f_, director; _g_, channel of poison. (After Carlet.)]

The Sting of the bee has been described in detail by Kraepelin, Sollmann, Carlet[3] and others. It is an extremely perfect mechanical arrangement. The sting itself—independent of the sheaths and adjuncts—consists of three elongate pieces, one of them a gouge-like director, the other two pointed and barbed needles; the director is provided with a bead for each of the needles to run on, these latter having a corresponding groove; the entrance to the groove is narrower than its subsequent diameter, so that the needles play up and down on the director with facility, but cannot be dragged away from it; each needle is provided with an arm at the base to which are attached the muscles for its movement. This simple manner of describing the mechanical arrangement is, however, incomplete, inasmuch as it includes no account of the means by which the poison is conveyed. This is done by a very complex set of modifications of all the parts; firstly, the director is enlarged at the anterior part to form a chamber, through which the needles play; the needles are each provided with a projecting piece, which, as the needle moves, plays in the chamber of the director, and forces downwards any liquid that may be therein; the poison-glands open into the chamber, and the projections on the needles, acting after the manner of a piston, carry the poison before them. The needles are so arranged on {7}the director that they enclose between themselves and it a space that forms the channel along which the poison flows, as it is carried forwards by the movement of the pistons attached to the needles. If the needles be thrust into an object quite as far as, or beyond, the point of the director much poison may be introduced into a wound, as the barbs are provided with small orifices placed one above the other, while if this be not the case much of the liquid will flow on the outside of the object.

According to Carlet the poison of the bee is formed by the mixture of the secretions of two glands, one of which is acid and the other alkaline; it is very deadly in its effects on other Insects. We shall see, however, that the Fossorial Hymenoptera, which catch and sting living prey for their young, frequently do not kill but only stupefy it, and Carlet states that in this group the alkaline gland is absent or atrophied, so that the poison consists only of the acid; it is thus, he thinks, deprived of its lethal power. Moreover, in the Fossoria the needles are destitute of barbs, so that the sting does not remain in the wound. Bordas, however, states[4] that in all the numerous Hymenoptera he has examined, both acid and alkaline glands exist, but exhibit considerable differences of form in the various groups. He gives no explanation of the variety of effects of the poison of different Aculeata.

The larvae (for figure of larva of _Bombus_, see Vol. V. p. 488) are, without known exception, legless grubs, of soft consistence, living entirely under cover, being protected either in cells, or, in the case of social Hymenoptera, in the abodes of the parents. The larvae of Ants and fossorial Hymenoptera have the anterior parts of the body long and narrow and abruptly flexed, so that their heads hang down in a helpless manner. All the larvae of Aculeates, so far as known, are remarkable from the fact that the posterior part of the alimentary canal does not connect with the stomach till the larval instar is more or less advanced; hence the food amongst which they live cannot be sullied by faecal matter. The pupa is invariably soft, and assumes gradually the colour of the perfect Insect. Almost nothing is known as to the intimate details of the metamorphosis, and very little as to the changes of external form. According to Packard a period intervenes between the stadium of the full-grown larva and that of the pupa, in which a series of changes he speaks of as semi-pupal {8}are passed through; these, however, have not been followed out in the case of any individual, and it is not possible to form any final idea about them, but it seems probable that they are largely changes of external shape, in conformity with the great changes going on in the internal organs. Owing to the fragmentary nature of observations, much obscurity and difference of opinion have existed as to the metamorphosis of Aculeate Hymenoptera. Sir S. Saunders gives the following statement as to the larva of a wasp of the genus _Psiliglossa_,[5] just before it assumes the pupal form: "The respective segments, which are very distinctly indicated, may be defined as follows:—The five anterior, including the head, are compactly welded together, and incapable of separate action in the pseudo-pupa state; the third, fourth, and fifth bearing a spiracle on either side. The thoracical region terminating here, the two anterior segments are assignable to the development of the imago head, as pointed out by Ratzeburg." This inference is not, however, correct. We have seen that in the perfect Insect of Petiolate Hymenoptera the first abdominal segment is fixed to the thorax, and Saunders' statement is interesting as showing that this assignment of parts already exists in the larva, but it in no way proves that the head of the imago is formed from the thorax of the larva. It has been stated that the larvae of the Aculeata have a different number of segments according to the sex, but this also is incorrect. The difference that exists in the perfect Insects in this respect is due to the withdrawal of the terminal three segments to the interior in the female, and of two only in the male. The larva consists of fourteen segments, and we find this number distributed in the female perfect Insect as follows: one constitutes the head, four segments the thorax and propodeum, followed by six external segments of the restricted abdomen, and three for the internal structures of the abdomen. This agrees with Forel's statement that in the ants the sting is placed in a chamber formed by three segments.

The development of the sting of the common bee has been studied by Dewitz.[6] It takes place in the last larval stage. Although nothing of the organ is visible externally in the adult larva, yet if such a larva be placed in spirit, there can be seen within the skin certain small appendages on the ventral surface of the penultimate and antepenultimate abdominal segments {9}(Fig. 4, A) placed two on the one, four on the other; these are the rudiments of the sting. In the course of development the terminal three segments are taken into the body, and the external pair of the appendages of the twelfth body segment (the ninth abdominal) become the sheaths of the sting, and the middle pair become the director; the pair of appendages on the eleventh segment give rise to the needles or spiculae. The sting-rudiments at an earlier stage (Fig. 4, C) are masses of hypodermis connected with tracheae; there is then but one pair on the twelfth segment, and this pair coalesce to form a single mass; the rudiments of the pair that form the director are differentiated secondarily from the primary pair of these masses of hypodermis. A good deal of discussion has taken place as to whether the component parts of the sting—gonapophyses—are to be considered as modifications of abdominal extremities (_i.e._ abdominal legs such as exist in Myriapods). Heymons is of opinion that this is not the case, but that the leg-rudiments and gonapophysal rudiments are quite distinct.[7] The origin of the sting of Hymenoptera (and of the ovipositor of parasitic Hymenoptera) is very similar to that of the ovipositor of _Locusta_ (Vol. V. p. 315 of this work), but there is much difference in the history of the development of the rudiments.

[Illustration: Fig. 4—Development of sting of the bee: A and C, ventral; B, side view. A, End of abdomen of adult larva: _a_, _b_, _c_, _d_, the last four segments, _c_ being the eleventh body segment, 11; _b_ bearing two pairs, and _c_ one pair, of rudiments. B, Tip of abdomen of adult bee: 9, the ninth, _d_, the tenth body segment. C, Rudiments in the early condition as seen within the body: _c_, first pair; _b_, the second pair not yet divided into two pairs; _b″_, _c′_, commencement of external growths from the internal projections. (After Dewitz.)]

Dewitz has also traced the development of the thoracic appendages in Hymenoptera.[8] Although no legs are visible in the adult larva, they really arise very early in the larval life from masses of hypodermis, and grow in the interior of the body, so that when the larva is adult the legs exist in a segmented though rudimentary condition in the interior of the body. Dewitz's study of the wing-development is less complete.

{10}Four primary divisions of Aculeates are generally recognised, viz. Anthophila (Bees), Diploptera (Wasps), Fossores (Solitary Wasps), Heterogyna (Ants). Though apparently they are natural, it is impossible to define them by characters that are without some exceptions, especially in the case of the males. Ashmead has recently proposed[9] to divide the Fossores; thus making five divisions as follows:—

Body with more or less of the hairs on it plumose 1. Anthophila.

Hairs of body not plumose.

Pronotum not reaching back to tegulae 2. Entomophila [= Fossores part]. Pronotum reaching back to tegulae.

Petiole (articulating segment of abdomen) simple without scales or nodes.

Front wings in repose with a fold making them narrow 3. Diploptera. Front wings not folded 4. Fossores [part].

Petiole with a scale or node (an irregular elevation on the upper side) 5. Heterogyna.

We shall here follow the usual method of treating all the fossorial wasps as forming a single group, uniting Ashmead's Entomophila and Fossores, as we think their separation is only valid for the purposes of a table; the Pompilidae placed by the American savant in Fossores being as much allied to Entomophila as they are to the other Fossores with which Ashmead associates them.

DIVISION I. ANTHOPHILA OR APIDAE—BEES.

_Some of the hairs of the body plumose; parts of the mouth elongated, sometimes to a great extent, so as to form a protrusible apparatus, usually tubular with a very flexible tip. Basal joint of hind foot elongate. No wingless adult forms; in some cases societies are formed, and then barren females called workers exist in great numbers, and carry on the industrial operations of the community. Food always derived from the vegetable kingdom, or from other Bees._

There are about 150 genera and 1500 species of bees at present known. Some call the division Mellifera instead of Anthophila. The term Apidae is used by some authorities to denote all the bees, while others limit this term to one of the families {11}or sub-divisions. The bees are, as a rule, distinguished from other Hymenoptera by the hairs, by the great development of the mouth parts to form a proboscis (usually, but not correctly, called tongue), and by the modification of the hind-legs; but these distinctive characters are in some of the species exhibited in so minor a degree of perfection that it is not easy to recognise these primitive forms as Anthophila. A few general remarks on the three points mentioned will enable the student to better appreciate the importance of certain points we shall subsequently deal with.

[Illustration: Fig. 5—Hairs of Bees: A, simple hair from abdomen of _Osmia_; B, spiral hair from abdomen of _Megachile_; C, plumose hair from thorax of _Megachile_; D, from thorax of _Andrena dorsata_; E, from thorax of _Prosopis_.]

The bees are, as a rule, much more covered with hair than any other of the Hymenoptera. Saunders[10] states that he has examined the structure of the hairs in all the genera of British Aculeata, and that in none but the Anthophila do branched and plumose hairs occur. The function of this kind of hairs is unknown; Saunders suggests[10] that they may be instrumental in the gathering of pollen, but they occur in the parasitic bees as well as in the males, neither of which gather pollen. The variety of the positions they occupy on the body seems to offer but little support to the suggestion. Not all the hairs of the bee's body are plumose, some are simple, as shown in Fig. 5, A, and this is specially the case with the hairs that are placed at the edges of the dilated plates for carrying pollen. In some forms there is an extensive system of simple hairs all over the body, and the "feathers" are distributed between these; and we do not see any reason for assuming that the feathered are superior to the simple hairs for gathering and carrying pollen. Some bees, _e.g._ _Prosopis_, _Ceratina_, have very little hair on the body, but nevertheless some plumose hairs are always present even though they be very short.

{12}[Illustration: Fig. 6—A, Worker of the honey-bee (_Apis mellifica_), with pollen plates laden; B, basal portions of a middle-leg (trochanter with part of coxa and of femur) with plumose hairs and grains of pollen; C, one hair bearing pollen-grains.]

The hind-legs of bees are very largely used in the industrial occupations of these indefatigable creatures; one of their chief functions in the female being to act as receptacles for carrying pollen to the nest: they exhibit, however, considerable diversity. The parts most modified are the tibia and the first joint of the hind-foot. Pollen is carried by other parts of the body in many bees, and even the hind-leg itself is used in different ways for the purpose: sometimes the outer face of the tibia is highly polished and its margins surrounded by hair, in which case pollen plates are said to exist (Fig. 6, A); sometimes the first joint of the tarsus is analogous to the tibia both in structure and function; in other cases the hind-legs are thick and densely covered with hair that retains the pollen between the separate hairs. In this case the pollen is carried home in a dry state, while, in the species with pollen plates, the pollen is made into a mass of a clay-like consistence.[11] The legs also assist in arranging the pollen on the other parts of the body. The males do not carry pollen, and though their hind-legs are also highly modified, yet the modifications do not agree with those of the female, and their functions are in all probability sexual. The parasitic bees also do not carry pollen, and exhibit another series of structures. The most interesting case in this series of modifications is that found in the genus _Apis_, where the hind-leg of male, female, and worker are all different (Fig. 25); the limb in the worker being highly modified for industrial purposes. This case has been frequently referred to, in consequence of the difficulty that exists in connection with its heredity, for the {13}structure exists in neither of the parents. It is, in fact, a case of a very special adaptation appearing in the majority of the individuals of each generation, though nothing of the sort occurs in either parent.

The proboscis of the bee[12] is a very complex organ, and in its extremely developed forms exhibits a complication of details and a delicacy of structure that elicit the admiration of all who study it. In the lower bees, however, especially in _Prosopis_, it exists in a comparatively simple form (Fig. 9, B, C), that differs but little from what is seen in some Vespidae or Fossores. The upper lip and the mandibles do not take any

## part in the formation of the bee's proboscis, which is consequently

entirely made up from the lower lip and the maxillae, the former of these two organs exhibiting the greatest modifications. The proboscis is situate on the lower part of the head, and in repose is not visible; a portion, and that by no means an inconsiderable one, of its modifications being for the purpose of its withdrawal and protection when not in use. For this object the under side of the head is provided with a very deep groove, in which the whole organ is, in bees with a short proboscis, withdrawn; in the Apidae with a long proboscis this groove also exists, and the basal part of the proboscis is buried in it during repose, while the other parts of the elongate organ are doubled on the basal part, so that they extend backwards under the body, and the front end or tip of the tongue is, when in repose, its most posterior part.

For the extrusion of the proboscis there exists a special apparatus that comes into play after the mandibles are unlocked and the labrum lifted. This extensive apparatus cannot be satisfactorily illustrated by a drawing, as the parts composing it are placed in different planes; but it may be described by saying that the cardo, or basal hinge of the maxilla, changes from an oblique to a vertical position, and thrusts the base of the proboscis out of the groove. The maxillae form the outer sheath of the proboscis, the lower lip its medial part (see Figs. 7 and 9); the base of the lower lip is attached to the submentum, which rises with the cardo so that labium and maxillae are lifted together; the co-operation of these two parts is effected by an angular piece called the lorum, in which the base of the submentum rests; the submentum is articulated with the mentum in such a manner that the two can either be placed in planes at a right angle to one another, or can be brought into one continuous plane, and by this change of plane the basal part of the tongue can also be thrust forwards.

{14}[Illustration: Fig. 7.—Side view of basal portions of proboscis of _Bombus_. _a_, Epipharyngeal sclerites; _b_, arrow indicating the position of the entrance to pharynx, which is concealed by the epipharynx, _c_; _d_, hypopharyngeal sclerites; _e_, vacant space between the scales of the maxillae through which the nectar comes: _f_, lobe; _f′_, stipes; _g_, cardo of maxilla: _h_, encephalic pillar on which the cardo swings; _i_, angle of junction of lores and submentum lorum; _k_, mentum; _l_, base of labial palp; _m_, maxillary palp.]

There is considerable variety in the lengths of these parts in different genera, and the lorum varies in shape in accordance with the length of the submentum. The lorum is a peculiar piece, and its mechanical adaptations are very remarkable; usually the base of the submentum rests in the angle formed by the junction of the two sides of the lorum, but in _Xylocopa_, where the submentum is unusually short, this part reposes in a groove on the back of the lorum, this latter having a very broad truncated apex instead of an angular one; in the condition of repose the apex of the lorum rests in a notch on the middle of the back of the oral groove, and in some of the forms with elongate submentum, this depression is transformed into a deep hole, or even a sort of tunnel, so as to permit the complete stowing away of the base of the tongue, which would otherwise be prevented by the long submentum; another function of the lorum appears to be that, as it extends, its arms have an outward thrust, and so separate the maxillae from the labium. In addition to these parts there are also four elongate, slender sclerites that are only brought into view on dissection, and that no doubt assist in correlating the movements of the parts of the mouth and {15}hypopharynx; one pair of these strap-like pieces extends backwards from the two sides of the base of the epipharynx; Huxley called them sclerites of the oesophagus; a better name would be epipharyngeal sclerites (Fig. 7, _a_): the other pair pass from the terminations of the epipharyngeal sclerites, along the front face of the hypopharynx, down to the mentum, their lower parts being concealed by the stipites of the maxillae; these are the hypopharyngeal sclerites, and we believe it will prove that they play a highly important part in deglutition. When the labrum of a bee is raised and the proboscis depressed, the epipharynx is seen hanging like a curtain from the roof of the head; this structure plays an important part in the act of deglutition. The entrance to the pharynx, or commencement of the alimentary canal, is placed below the base of the epipharynx. As we are not aware of any good delineations of the basal parts of the proboscis we give a figure thereof (Fig. 7). The maxillae in the higher bees are extremely modified so as to form a sheath, and their palpi are minute; in the lower bees the palpi have the structure usual in mandibulate Insects.

Returning to the consideration of the lower lip, we find that there is attached to the mentum a pair of elongate organs that extend forwards and form a tube or sheath, enclosed by the maxillary sheath we have previously mentioned; these are the greatly modified labial palpi, their distal parts still retaining the palpar form; and in the lower bees the labial palpi are, like the maxillary, of the form usual in mandibulate Insects. Between the labial palps and the central organ of the lip there is attached a pair of delicate organs, the paraglossae.

There remains for consideration the most remarkable part of the proboscis, the long, delicate, hairy organ which the bee thrusts out from the tip of the shining tube formed by the labial palps and the maxillae, described above, and which looks like a prolongation of the mentum. This organ is variously called ligula, lingua, or tongue.[13] We prefer the first of these names.

According to Breithaupt and Cheshire the structure of the ligula is highly remarkable; it is a tube (filled with fluid from the body cavity), and with a groove underneath caused by a large part of the circumference of the tube being invaginated; the {16}invaginated part can be thrust out by increase of the pressure of the fluid in the tube. A portion of the wall of the invaginate part is thickened so as to form a chitinous rod.

This description will suffice for present purposes, as the other parts of the mouth will be readily recognised by the aid of figure 9, A, B, C. In the exquisitely endowed South American genus _Euglossa_ (Fig. 18), the proboscis is somewhat longer than the whole of the body, so that its tip in repose projects behind the body like a sting.

[Illustration: Fig. 8.—Transverse section of ligula of honey-bee, diagramatic. A, With the long sac invaginate. B, evaginate: _a_, chitinous envelope with the bases of the hairs; _b_, rod; _c_, groove of rod; _d_, lumen due in A to invagination of the rod, in B to its evagination; _n_, nerve; _tr_, trachea.]

The correct nomenclature of the parts connected with the lower lip is not definitely settled, authorities not being agreed on several points. The whole of the proboscis is usually called the tongue; this, however, is admittedly an erroneous application of this term. The terminal delicate, elongate, flexible organ is by some called the tongue; but this again is wrong: the lingua in Insects is the hypopharynx; this part is developed in a peculiar manner in bees, but as it is not tongue-like in shape, the term lingua is not suitable for it, and should be dismissed altogether from the nomenclature of the bee's trophi; it is used at present in two different senses, both of which are erroneous. We see no objection to describing the flexible apical portion of the proboscis as the ligula. The lorum is probably a special part peculiar to the higher bees; according to Saunders it is not present as a specialised part in some of the primitive forms.[14] The application of the terms mentum, submentum and hypoglottis is open to the same doubts that exist with regard to them in so many other {17}Insects, and we have omitted the term hypoglottis altogether, though some may think the mentum entitled to that name.

[Illustration: Fig. 9.—A, Proboscis of a "long-tongued" bee, _Anthophora pilipes_; B, lower, C, upper view of proboscis of an "obtuse-tongued" bee, _Prosopis pubescens_. _a_, Labrum; _b_, stipes; _c_, palpiger; _d_, scale: _f_, lobe; _g_, palpus; _h_, cardo, of maxilla: _i_, lorum; _k_, submentum; _l_, mentum; _m_, labial palp; _n_, paraglossa; _o_, ligula; _p_, tip of ligula (with "spoon" at tip and some of the hairs more magnified); _q_, hypopharyngeal sclerites.]

The way in which the proboscis of the bee acts has been very largely discussed, with special reference to the question as to whether it is a sucking or a licking action. It is impossible to consider either of these terms as applicable. The foundation of the action is capillary attraction, by which, and by slight movements of increase and contraction of the capacity of various parts, the fluid travels to the cavity in front of the hypopharynx: here the scales of the maxillae leave a vacant space, (Fig. 7, _e_) so that a cup or cavity is formed, the fluid in which is within reach of the tip of the dependent epipharynx (_c_), which hangs down over the front of the hypopharynx (and is so shaped that its tip covers the cup); it is between these two parts that the fluid passes to reach the pharynx. It is no doubt to slight movements of the membranous parts of the hypopharynx and of the epipharynx that the further progress of the nectar is due, aided by contraction and expansion of the pharynx, induced by muscles attached to it. It should be recollected that in addition to the movements of the head itself, the hypopharynx is constantly changing its dimensions slightly by the impulses of the fluid of the general body cavity; also that the head changes its position, {18}and that the proboscis is directed downwards as well as forwards. Those who wish to pursue this subject should refer to the works of Breithaupt[15] and Cheshire.

The other external characters of the Bees call for little remark. The pronotum is never very large or much prolonged in front, and its hind angles never repose on the tegulae as they do in the wasps,[16] but extend backwards below the tegulae. The hind body is never narrowed at the base into an elongate pedicel, as it so frequently is in the Wasps and in the Fossors; and the propodeum (the posterior part of the thorax) is more perpendicular and rarely so largely developed as it is in the Fossors; this last character will as a rule permit a bee to be recognised at a glance from the fossorial Hymenoptera.

Bees, as every one knows, frequent flowers, and it is usually incorrectly said that they extract honey. They really gather nectar, swallow it, so that it goes as far as the crop of their alimentary canal, called in English the honey-sac, and is regurgitated as honey. Bertrand states that the nectar when gathered is almost entirely pure saccharose, and that when regurgitated it is found to consist of dextrose and levulose:[17] this change appears to be practically the conversion of cane- into grape-sugar. A small quantity of the products of the salivary glands is added, and this probably causes the change alluded to; so that honey and nectar are by no means synonymous. According to Cheshire the glandular matter is added while the nectar is being sucked, and is passing over the middle parts of the lower lip, so that the nectar may be honey when swallowed by the bee. In addition to gathering nectar the female bees are largely occupied in collecting pollen, which, mixed with honey, is to serve as food for the colony. Many, if not all, bees eat pollen while collecting it. The mode in which they accumulate the pollen, and the mechanism of its conveyance from hair to hair till it reaches the part of the body it must attain in order to be removed for packing in the cells, is not fully understood, but it appears to be accomplished by complex correlative actions of various parts; the head and the front legs scratch up the pollen, the legs move with great rapidity, and the pollen ultimately reaches its destination. The workers of the genus _Apis_, and of some other social {19}bees, have the basal joint of the hind foot specially adapted to deal with pollen (Fig. 25, 2). We have already mentioned the modifications of the legs used for its conveyance, and need here only add that numerous bees—the Dasygastres—carry the pollen by aid of a special and dense clothing of hairs on the underside of the abdomen.

The buzzing of bees (and other Insects) has been for long a subject of controversy: some having maintained that it is partially or wholly due to the vibration of parts connected with the spiracles, while others have found its cause in the vibrations of the wings. According to the observations of Pérez and Bellesme,[18] two distinct sounds are to be distinguished. One, a deep noise, is due to the vibration of the wings, and is produced whenever a certain rapidity is attained; the other is an acute sound, and is said to be produced by the vibrations of the walls of the thorax, to which muscles are attached; this sound is specially evident in Diptera and Hymenoptera, because the integument is of the right consistence for vibration. Both of these observers agree that the spiracles are not concerned in the matter.

The young of bees are invariably reared in cells. These (except in the case of the parasitical bees) are constructed by the mothers, or by the transformed females called workers. The solitary bees store the cells with food, and close up each cell after having laid an egg in it, so that in these cases each larva consumes a special store previously provided for it. The social bees do not close the cells in which the larvae are placed, and the workers act as foster-mothers, feeding the young larvae after the same fashion as birds feed their nestling young. The food is a mixture of honey and pollen, the mixing being effected in various ways and proportions according to the species; the honey seems to be particularly suitable to the digestive organs of the young larvae, and those bees that make closed cells, place on the outside of the mass of food a layer more thickly saturated with honey, and this layer the young grub consumes before attacking the drier parts of the provisions. The active life of the larva is quite short, but after the larva is full-grown it usually passes a more or less prolonged period in a state of quiescence before assuming the pupal form. The pupa shows the limbs and other parts of the perfect Insect in a very distinct manner, and the {20}development of the imago takes place gradually though quickly. Some larvae spin cocoons, others do not.

A very large number of bees are parasitic in their habits, laying an egg, or sometimes more than one, in the cell of a working bee of some species other than their own; in such cases the resulting larvae eat and grow more quickly than the progeny of the host bee, and so cause it to die of starvation. It has been observed that some of these parasitic larvae, after eating all the store of food, then devour the larva they have robbed. In other cases it is possible that the first care of the parasitic larva, after hatching, is to eat the rival egg.

The taxonomy of bees is in a very unsatisfactory state. The earlier Hymenopterists were divided into two schools, one of which proposed to classify the bees according to their habits, while the other adopted an arrangement depending on the length of the parts of the mouth, the development of the palpi, and the form and positions of the organs for carrying pollen. Neither of these arrangements was at all satisfactory, and some entomologists endeavoured to combine them, the result being a classification founded partly on habits and partly on certain minor structural characters. This course has also proved unsatisfactory; this is especially the case with exotic bees, which have been placed in groups that are defined by habits, although very little observation has actually been made on this point. Efforts have recently been made to establish an improved classification, but as they relate solely to the European bees they are insufficient for general purposes.

The more important of the groups that have been recognised are—(1) the Obtusilingues, short-tongued bees, with the tip of the lingua bifid or broad; (2) Acutilingues, short-tongued bees, with acute tip to the tongue; these two groups being frequently treated of as forming the Andrenidae. Coming to the Apidae, or the bees with long and folded tongues, there have been distinguished (3) Scopulipedes, bees carrying pollen with their feet, and (4) Dasygastres, those that carry it under the abdomen; some of the parasitic and other forms have been separated as (5) Denudatae (or Cuculinae); the Bombi and the more perfectly social bees forming another group, viz. (6) Sociales. A group Andrenoides, or Panurgides, was also proposed for certain bees considered to belong to the Apidae though exhibiting many points of {21}resemblance with the Andrenidae. This arrangement is by no means satisfactory, but as the tropical bees have been but little collected, and are only very imperfectly known, it is clear that we cannot hope for a better classification till collections have been very much increased and improved. The arrangement adopted in Dalla Torre's recent valuable catalogue of bees[19] recognises no less than fourteen primary divisions, but is far from satisfactory.

[Illustration: Fig. 10—_Prosopis signata._ Cambridge. A, Female; B, front of head of female; C, of male.]

The two genera _Prosopis_ and _Sphecodes_ have been recently formed into a special family, Archiapidae, by Friese,[20] who, however, admits that the association is not a natural one. The term should be limited to _Prosopis_ and the genera into which it has been, or shortly will be, divided. The primitive nature of the members of this genus is exhibited in all the external characters that are most distinctive of bees; the proboscis (Fig. 9, B, C), is quite short, its ligula being very short, and instead of being pointed having a concave front margin. The body is almost bare, though there is some very short feathered plumage. The hind legs are destitute of modifications for industrial purposes. Owing to these peculiarities it was for long assumed that the species of _Prosopis_ must be parasites. This is, however, known not to be the case so far as many of the species are concerned. They form cells lined with a silken membrane in the stems of brambles and other plants that are suitable, or in burrows in the earth, or in the mortar of walls; individuals of the same species varying much as to the nidus they select. The food they store in these cells is much more liquid than usual, and has been supposed to be entirely honey, since they have no apparatus for carrying pollen. Mr. R. C. L. Perkins has, however, observed that they swallow both pollen and nectar, brushing the first-named substance to the mouth by aid of the front legs. He {22}has ascertained that a few of the very numerous Hawaiian species of the genus are really parasitic on their congeners: these parasites are destitute of a peculiar arrangement of hairs on the front legs of the female, the possession of which, by some of the non-parasitic forms, enables the bee to sweep the pollen towards its mouth. These observations show that the structural peculiarities of _Prosopis_ are correlative with the habits of forming a peculiar lining to the cell, and of gathering pollen by the mouth and conveying it by the alimentary canal instead of by external parts of the body. _Prosopis_ is a very widely distributed genus, and very numerous in species. We have ten in Britain; several of them occur in the grounds of our Museum at Cambridge.

The species of the genus _Colletes_ are hairy bees of moderate size, with a good development of hair on the middle and posterior femora for carrying pollen. They have a short, bilobed ligula like that of wasps, and therein differ from the Andrenae, which they much resemble. With _Prosopis_ they form the group Obtusilingues of some taxonomists. They have a manner of nesting peculiar to themselves; they dig cylindrical burrows in the earth, line them with a sort of slime, that dries to a substance like gold-beater's skin, and then by partitions arrange the burrow as six to ten separate cells, each of which is filled with food that is more liquid than usual in bees. Except in regard to the ligula and the nature of the cell-lining, _Colletes_ has but little resemblance to _Prosopis_; but the term Obtusilingues may be applied to _Colletes_ if _Prosopis_ be separated as Archiapidae. We have six species of _Colletes_ in Britain.

_Sphecodes_ is a genus that has been the subject of prolonged difference of opinion. The species are rather small shining bees, with a red, or red and black, abdomen, almost without pollen-collecting apparatus, and with a short but pointed ligula. These characters led to the belief that the Insects are parasitic, or, as they are sometimes called, cuckoo-bees. But evidence could not be obtained of the fact, and as they were seen to make burrows it was decided that we have in _Sphecodes_ examples of industrial bees extremely ill endowed for their work. Recent observations tend, however, to prove that _Sphecodes_ are to a large extent parasitic at the expense of bees of the genera _Halictus_ and _Andrena_. Breitenbach has taken _S. rubicundus_ out of the brood-cells of _Halictus quadricinctus_; and on one of the few {23}occasions on which this bee has been found in Britain it was in circumstances that left little doubt as to its being a parasite of _Andrena nigroaenea_. Marchal[21] has seen _S. subquadratus_ fight with _Halictus malachurus_, and kill it previous to taking possession of its burrows; and similar observations have been made by Ferton. As the older observations of Smith, Sichel, and Friese leave little doubt that _Sphecodes_ are sometimes industrial bees, it is highly probable that we have in this genus the interesting condition of bees that are sometimes parasitic, at other times not; but so much obscurity still prevails as to the habits of _Sphecodes_ that we should do well to delay accepting the theories that have been already based on this strange state of matters.[22] Friese states that in _Sphecodes_ the first traces of collecting apparatus exist; and, accepting the condition of affairs as being that mentioned above, it is by no means clear whether we have in _Sphecodes_ bees that are abandoning the parasitic habit or commencing it; or, indeed, whether the condition of uncertainty may not be a permanent one. It is difficult to decide as to what forms are species in _Sphecodes_ owing to the great variation. The Hymenopterist Forster considered that 600 specimens submitted to him by Sichel represented no less than 140 species, though Sichel was convinced that nearly the whole of them were one species, _S. gibbus_. It has recently been found that the male sexual organs afford a satisfactory criterion. The position of _Sphecodes_ in classification is doubtful.

[Illustration: Fig. 11.—_Sphecodes gibbus_ ♀. Britain.]

The great majority of the species of short-tongued bees found in Britain belong to the genera _Andrena_ and _Halictus_, and with some others constitute the Andrenides of many writers. _Halictus_ includes our smallest British bees. Their economy escaped the earlier observers, but has recently been to some extent unravelled by Smith, Fabre, Nicolas, Verhoeff, and others, and proves to be {24}of great interest and variety. Fabre observed _H. lineolatus_ and _H. sexcinctus_[23] under circumstances that enabled him to give them continuous attention, whenever requisite, throughout a whole year. These bees are to a certain extent social; they are gregarious; each bee works for its own progeny, but there is collaboration between members of a colony, inasmuch as a piece of general work is undertaken from which more families than one derive benefit. This common work is a gallery, that, ramifying in the earth, gives access to various groups of cells, each group the production of a single _Halictus_; in this way one entrance and one corridor serve for several distinct dwellings. The work of excavation is carried on at night. The cells are oval, and are covered on the interior with a delicate waterproof varnish; Fabre considers this to be a product of the salivary glands, like the membrane we noticed when speaking of _Colletes_. In the south of France both sexes of these species are produced from the nests in September, and then the males are much more numerous than the females; when the cold weather sets in the males die, but the females continue to live on in the cells underground. In the following spring the females come out and recommence working at the burrows, and also provision the cells for the young; the new generation, consisting entirely of females, appears in July, and from these there proceeds a parthenogenetic generation, which assumes the perfect form in September, and consists, as we have above remarked, in greater part of males. Pérez,[24] however, considers that Fabre's observations as to the parthenogenetic generation were incomplete, and that males might have been found a little earlier, and he consequently rejects altogether the occurrence of parthenogenesis in _Halictus_. Nicolas confirms Fabre's observations, so far as the interesting point of the work done for common benefit is concerned; and adds that the common corridor being too narrow to permit of two bees passing, there is a dilatation or vestibule near the entrance that facilitates passage, and also that a sentinel is stationed at this point.

Smith's observations on _Halictus morio_ in England lead one to infer that there is but one generation, the appearance of which extends over a very long period. He says, "Early in April the females appeared, and continued in numbers up to the end of {25}June"; then there was an interval, and in the middle of August males began to appear, followed in ten or twelve days by females. Hence it is probable that in different countries the times of appearance and the number of generations of the same species may vary. Verhoeff has described the burrows of _Halictus quadricinctus_ with some detail. The cells, instead of being distributed as usual throughout the length of the burrow one by one, are accumulated into a mass placed in a vault communicating with the shaft. This shaft is continued downwards to a depth of 10 cm., and forms a retreat for the bees when engaged in construction. Several advantages are secured by this method, especially better ventilation, and protection from any water that may enter the shaft. The larvae that are present in the brood-chambers at any one moment differ much in their ages, a fact that throws some doubt on the supposed parthenogenetic generation. No cocoons are formed by these _Halictus_, the polished interior of the cell being a sufficiently refined resting place for metamorphosis. Verhoeff states that many of the larvae are destroyed by mouldiness; this indeed, he considers to be the most deadly of the enemies of Aculeate Hymenoptera. The nest of _Halictus maculatus_ has also been briefly described by Verhoeff, and is a very poor construction in comparison with that of _H. quadricinctus_.

[Illustration: Fig. 12—Nesting of _Halictus quadricinctus_. _u_, Original burrow, with entrance _e_ thereto; _n_, retreat or continuation of the burrow; _w_, the vaults; _s_, the accumulation of cells. (After Verhoeff, _Verh. Ver. Rheinl._ xlviii. 1891; scale not mentioned.)]

The genus _Andrena_ includes a great number of species, Britain possessing about fifty. They may be described in a general manner as Insects much resembling the honey-bee—for which, indeed, they are frequently mistaken—but usually a little smaller in size. Many of the bees we see in spring, in March or April, are of this genus. They live in burrows in the ground, preferring sandy places, but frequently selecting a gravel path as the locality for their operations; they nearly always live {26}in colonies. Great difficulties attend their study on account of several points in their economy, such as, that the sexes are different, and frequently not found together; also that there may be two generations of a species in one year, these being more or less different from one another. Another considerable difficulty arises from the fact that these bees are subject to the attacks of the parasite _Stylops_, by which their form is more or less altered. These Insects feed in the body of the bee in such a way as to affect its nutrition without destroying its life; hence they offer a means of making experiments that may throw valuable light on obscure physiological questions. Among the effects they produce in the condition of the imago bee we may mention the enfeeblement of the sexual distinction, so that a stylopised male bee becomes less different than it usually is from the female, and a stylopised female may be ill developed and less different than usual from the male. The colours and hair are sometimes altered, and distortion of portions of the abdominal region of the bee are very common. Further particulars as to these parasites will be found at the end of our account of Coleoptera (p. 298). We may here remark that these _Stylops_ are not the only parasitic Insects that live in the bodies of Andrenidae without killing their hosts, or even interrupting their metamorphoses. Mr. R. C. L. Perkins recently captured a specimen of _Halictus rubicundus_, from which he, judging from the appearance of the example, anticipated that a _Stylops_ would emerge; but instead of this a Dipterous Insect of the family Chloropidae appeared. Dufour in 1837 called attention to a remarkable relation existing between _Andrena aterrima_ and a parasitic Dipterous larva. The larva takes up a position in the interior of the bee's body so as to be partly included in one of the great tracheal vesicles at the base of the abdomen; and the bee then maintains the parasite in its position, and at the same time supplies it with air by causing two tracheae to grow into its body. Dufour states that he demonstrated the continuity of the tracheae of the two organisms, but it is by no means clear that the continuity was initially due to the bee's organisation.

[Illustration: Fig. 13—Parasitic Dipterous larva in connection with tracheal system of _Andrena aterrima_. (After Dufour.)]

{27}[Illustration: Fig. 14.—_D. hirtipes_ ♀. Britain.]

_Dasypoda hirtipes_ appears to be the most highly endowed of the European Andrenides. The Insects of the genus _Dasypoda_ are very like _Andrena_, but have only two in place of three submarginal cells (just beneath the stigma) on the front wing. The female of _D. hirtipes_ has a very dense and elongate pubescence on the posterior legs, and carries loads of pollen, each about half its own weight, to its nest. The habits of this insect have been described by Hermann Müller.[25] It forms burrows in the ground after the fashion of _Andrena_; this task is accomplished by excavating with the mandibles; when it has detached a certain quantity of the earth it brings this to the surface by moving backwards, and then distributes the loose soil over a considerable area. It accomplishes this in a most beautiful manner by means of the combined action of all the legs, each pair of these limbs performing its share of the function in a different manner; the front legs acting with great rapidity—making four movements in a second—push the sand backwards under the body, the bee moving itself at the same time in this direction by means of the middle pair of legs; simultaneously, but with a much slower movement, the hind legs are stretched and moved outwards, in oar-like fashion, from the body, and thus sweep away the earth and distribute it towards each side. This being done the bee returns quickly into the hole, excavates some more earth, brings it up and distributes it. Each operation of excavation takes a minute or two, the distribution on the surface only about fifteen seconds. The burrow extends to the length of one or two feet, so that a considerable amount of earth has to be brought up; and when the Insect has covered one part of the circumference of the mouth of the hole with loose earth, it makes another patch, or walk, by the side of the first. The main burrow being completed, the Insect then commences the formation of brood-chambers in connection with it. Three to six such chambers are formed in connection with a burrow; the lower one is first made and is provisioned by the bee: for this {28}purpose five or six loads of pollen are brought to the cell, each load being, as we have already remarked, about half the weight of the Insect. This material is then formed into a ball and made damp with honey; then another load of pollen is brought, is mixed with honey and added as an outer layer to the ball, which is now remodelled and provided on one side with three short feet, after which an egg is placed on the top of the mass; the bee then sets to work to make a second chamber, and uses the material resulting from the excavation of this to close completely the first chamber. The other chambers are subsequently formed in a similar manner, and then the burrow itself is filled up. While engaged in ascertaining these facts, Müller also made some observations on the way the bee acts when disturbed in its operations, and his observations on this point show a very similar instinct to that displayed by _Chalicodoma_, referred to on a subsequent page. If interrupted while storing a chamber the Insect will not attempt to make a fresh one, but will carry its stock of provisions to the nest of some other individual. The result of this proceeding is a struggle between the two bees, from which it is satisfactory to learn that the rightful proprietor always comes out victorious. The egg placed on the pollen-ball in the chamber hatches in a few days, giving birth to a delicate white larva of curved form. This creature embraces the pollen-ball so far as its small size will enable it to do so, and eats the food layer by layer so as to preserve its circular form. The larva when hatched has no anal orifice and voids no excrement, so that its food is not polluted; a proper moulting apparently does not take place, for though a new delicate skin may be found beneath the old one this latter is not definitely cast off. When the food, which was at first 100 to 140 times larger than the egg or young larva, is all consumed the creature then for the first time voids its refuse. During its growth the larva becomes red and increases in weight from .0025 grains to .26 or .35 grains, but during the subsequent period of excretion it diminishes to .09 or .15 grains, and in the course of doing so becomes a grub without power of movement, and of a white instead of a red colour. After this the larva reposes motionless for many months—in fact, until the next summer, when it throws off the larval skin and appears as a pupa. The larval skin thus cast off contrasts greatly with the previous delicate {29}condition of the integument, for this last exuvium is thick and rigid. Although it voids no excrement till much later the union of the stomach and hind-intestine is accomplished when the larva is half-grown. A larva, from which Müller took away a portion of its unconsumed food-store, began directly afterwards to emit excrement. The pupa has greater power of movement than the resting larva; when it has completed its metamorphosis and become a perfect Insect, it, if it be a female, commences almost immediately after its emergence to form burrows by the complex and perfect series of actions we have described.

PARASITIC BEES (Denudatae).—This group of parasitic bees includes fourteen European genera, of which six are British. They form a group taxonomically most unsatisfactory, the members having little in common except the negative characters of the absence of pollen-carrying apparatus. Although there is a great dearth of information as to the life-histories of parasitic bees, yet some highly interesting facts and generalisations about their relations with their hosts have already been obtained. Verhoeff has recently given the following account of the relations between the parasitic bee _Stelis minuta_ and its host _Osmia leucomelana_:—The _Osmia_ forms cells in blackberry stems, provisions them in the usual manner, and deposits an egg in each. But the _Stelis_ lays an egg in the store of provisions before the _Osmia_ does, and thus its egg is placed lower down in the mass of food than that of the legitimate owner, which is in fact at the top. The _Stelis_ larva emerges from the egg somewhat earlier than the _Osmia_ larva does. For a considerable time the two larvae so disclosed consume together the stock of provisions, the _Osmia_ at the upper, the _Stelis_ at the lower, end thereof. By the consumption of the provisions the two larvae are brought into proximity, and by this time the _Stelis_ larva, being about twice the size of the _Osmia_ larva, kills and eats it. Verhoeff witnessed the struggle between the two larvae, and states further that the operation of eating the _Osmia_ larva after it has been killed lasts one or two days. He adds that parasitic larvae are less numerous than the host larvae, it being well known that parasitic bees produce fewer offspring than host bees. Verhoeff further states that he has observed similar relations to obtain between the larvae of other parasitic bees and their hosts, but warns us against concluding that the facts are analogous in all cases.

{30}[Illustration: Fig. 15.—_Nomada sex-fasciata_ ♀. Britain.]

Fabre has made us acquainted with some points in the history of another species of the same genus, viz. _Stelis nasuta_, that show a decided departure from the habits of _S. minuta_. The first-named Insect accomplishes the very difficult task of breaking open the cells of the mason-bee, _Chalicodoma muraria_, after they have been sealed up, and then, being an Insect of much smaller size than the _Chalicodoma_, places several eggs in one cell of that bee. Friese informs us that parasitic bees and their hosts, in a great number of cases, not only have in the perfect state the tongue similarly formed, but also frequent the same species of flower; thus _Colletes daviesanus_ and its parasite _Epeolus variegatus_ both specially affect the flowers of _Tanacetum vulgare_. Some of the parasitic bees have a great resemblance to their hosts; _Stelis signata_, for instance, is said to be so like _Anthidium strigatum_ that for many years it was considered to be a species of the genus _Anthidium_. In other cases not the least resemblance exists between the parasites and hosts. Thus the species of _Nomada_ that live at the expense of species of the genus _Andrena_ have no resemblance thereto. Friese further tells us that the _Andrena_ and _Nomada_ are on the most friendly terms. _Andrena_, as is well known, forms populous colonies in banks, paths, etc., and in these colonies the destroying _Nomada_ flies about unmolested; indeed, according to Friese, it is treated as a welcome guest. He says he has often seen, and in several localities, _Nomada lathburiana_ and _Andrena ovina_ flying peacefully together. The _Nomada_ would enter a burrow, and if it found the _Andrena_ therein, would come out and try another burrow; if when a marauding _Nomada_ was in a burrow, and the rightful owner, returning laden with pollen, found on entering its home that an uninvited guest was therein, the _Andrena_ would go out in order to permit the exit of the _Nomada_, and then would again enter and add the pollen to the store. Strange as this may seem at first sight, it is really not so, for, as we have before had occasion to observe, there is not the slightest reason for believing that host Insects have any idea whatever that the parasites or inquilines are injurious to their {31}race. Why then should they attack the creatures? Provided the parasites do not interfere in any unmannerly way with the hosts and their work, there is no reason why the latter should resent their presence. The wild bee that seals up its cell when it has laid an egg therein, and then leaves it for ever, has no conception of the form of its progeny; never in the history of the race of the _Andrena_ has a larva seen a perfect insect and survived thereafter, never has a perfect Insect seen a larva. There is no reason whatever for believing that these Insects have the least conception of their own metamorphosis, and how then should they have any idea of the metamorphosis of the parasite? If the _Andrena_ found in the pollen the egg of a parasitic _Nomada_, it could of course easily remove the egg; but the _Andrena_ has no conception that the presence of the egg ensures the death of its own offspring and though the egg be that of an enemy to its race, why should it resent the fact? Is it not clear that the race has always maintained itself notwithstanding the enemy? Nature has brought about that both host and parasite should successfully co-exist; and each individual of each species lives, not for itself, but for the continuance of the species; that continuance is provided for by the relative fecundities of host and guest. Why then should the _Andrena_ feel alarm? If the species of _Nomada_ attack the species of _Andrena_ too much it brings about the destruction of its own species more certainly than that of the _Andrena_.

[Illustration: Fig. 16.—_Melecta luctuosa_ ♀. Britain.]

Such extremely friendly relations do not, however, exist between all the parasitic bees and their hosts. Friese says that, so far as he has been able to observe, the relations between the two are not in general friendly. He states that marauders of the genera _Melecta_ and _Coelioxys_ seek to get out of the way when they see the pollen-laden host coming home. But he does not appear to have noted any other evidence of mistrust between the two, and it is somewhat doubtful whether this act can properly be interpreted as indicating fear, for bees, as well as other animals, when engaged in work find it annoying to be interfered {32}with; it is the interest of the parasite to avoid annoyance and to be well-mannered in its approaches. Shuckard, however, says that battles ensue between the parasite _Melecta_ and its host _Anthophora_, when the two bees meet in the burrows of the _Anthophora_.[26]

We shall have occasion to remark on some of the habits of _Dioxys cincta_ when considering the history of the mason-bee (_Chalicodoma_), but one very curious point in its economy must here be noticed. The _Dioxys_, which is a much smaller bee than the _Chalicodoma_, lays an egg in a cell of the latter, and the resulting larva frequently has more food in the cell than it can consume; there is, however, another bee, _Osmia cyanoxantha_, that frequently takes advantage of an unoccupied cell in the nest of the _Chalicodoma_, and establishes its own offspring therein. The _Dioxys_, it seems, cannot, or at any rate does not, distinguish whether a cell is occupied by _Chalicodoma_ or by _Osmia_, and sometimes lays its egg in the nest of the _Osmia_, though this bee is small, and therefore provides very little food for its young. It might be supposed that under these conditions the _Dioxys_ larva would be starved to death; but this is not so; it has the power of accommodating its appetite, or its capacity for metamorphosis, to the quantity of food it finds at its disposal, and the egg laid in the _Osmia_ cell actually produces a tiny specimen of _Dioxys_, only about half the natural size. Both sexes of these dwarf _Dioxys_ are produced, offering another example of the fact that the quantity of food ingested during the lifetime of the larva does not influence the sex of the resulting imago.

The highly endowed bees that remain to be considered are by some writers united in a group called Apidae, in distinction from Andrenidae. For the purposes of this work we shall adopt three divisions, Scopulipedes, Dasygastres, Sociales.

The group Scopulipedes includes such long-tongued, solitary bees as are not parasitic, and do not belong to the Dasygastres. It is not, however, a natural group, for the carpenter-bees (_Xylocopa_) are very different from _Anthophora_. It has recently been merged by Friese with Andrenides into a single group called Podilegidae. Four British genera, _Ceratina_, _Anthophora_, _Eucera_ and _Saropoda_ (including, however, only seven {33}species), are referred to the Scopulipedes; in some forms a considerable resemblance to the Bombi is exhibited, indeed the female of one of our species of _Anthophora_ is so very like the worker of _Bombus hortorum_ var. _harrisellus_, that it would puzzle any one to distinguish them by a superficial inspection, the colour of the hair on the hind legs being the only obvious difference. _Anthophora_ is one of the most extensive and widely distributed of the genera of bees. Some of the species make burrows in cliffs and form large colonies which are continued for many years in the same locality. Friese has published many details of the industry and metamorphoses of some of the species of this genus; the most remarkable point he has discovered being that _A. personata_ at Strasburg takes two years to accomplish the life-cycle of one generation. Some of the European species of the genus have been found to be very subject to the attacks of parasites. An anomalous beetle, _Sitaris_, has been found in the nests of _A. pilipes_; and this same _Anthophora_ is also parasitised by another beetle, _Meloe_, as well as by a bee of the genus _Melecta_.

The genus _Xylocopa_[27] contains many of the largest and most powerful of the bees, and is very widely distributed over the earth. In Europe only four or five species have been found, and none of them extend far northwards, _X. violacea_ being the only one that comes so far as Paris. They are usually black or blue-black in colour, of broad, robust build, with shining integuments more or less covered with hair. _X. violacea_ is known as the carpenter-bee from its habit of working in dry wood; it does not touch living timber, but will form its nest in all sorts of dried wood. It makes a cylindrical hole, and this gives access to three or four parallel galleries in which the broad cells are placed; the cells are always isolated by a partition; the bee forms this by cementing together with the products of its salivary glands the fragments of wood it cuts out. Its habits have been described at length by Réaumur, who alludes to it under the name of "abeille perce-bois." This bee hibernates in the imago condition, both sexes reappearing in the spring. Possibly there is more than one generation in the year, as Réaumur states that specimens that were tiny larvae on the 12th of June had by the 2nd of July consumed all their stock of provisions; they then fasted for a few days, and on the 7th or 8th of July became pupae, and in the first {34}days of August were ready to emerge as perfect Insects. Thus the whole cycle of metamorphoses is passed through in about eight weeks. This species, though very clever in drilling holes, does not hesitate to appropriate old burrows should they be at hand. Fabre observed that it was also quite willing to save itself labour by forming its cells in hollow reeds of sufficient calibre. We have figured the larva and pupa of this species in the previous volume (p. 170).

[Illustration: Fig. 17.—_Xylocopa_ (_Koptorthosoma_), sp. near _flavonigrescens_, ♂. Sarawak.]

_Xylocopa chloroptera_ in E. India selects a hollow bamboo for its nidus; it cements together the pieces obtained in clearing out the bamboo, and uses them as horizontal partitions to separate the tube into cells. The species is much infested with a small Chalcid of the genus _Encyrtus_: 300 specimens of the parasite have been reared from a single larva of the bee; two-thirds of the larvae of this bee that Horne endeavoured to rear were destroyed by the little Chalcid.

The most beautiful and remarkable of all the bees are the species of _Euglossa_. This genus is peculiar to Tropical America, and derives its name from the great length of the proboscis, which in some species surpasses that of the body. The colours in _Euglossa_ proper are violet, purple, golden, and metallic green, and two of these are frequently combined in the most harmonious manner; the hind tibia is greatly developed and forms a plate, the outer surface of which is highly polished, while the margins are furnished with rigid hairs. Very little is known as to the habits of these bees; they were formerly supposed to be {35}social; but this is doubtful, Bates having recorded that _E. surinamensis_ forms a "solitary nest." Lucas concluded that _E. cordata_ is social, on the authority of a nest containing "a dozen individuals." No workers are known. The species of _Eulema_ have a shorter tongue than _Euglossa_, and in form and colour a good deal resemble our species of _Bombus_ and _Apathus_.

The group Dasygastres includes seven European genera, four being British (_Chelostoma_ being included in _Heriades_). The ventral surface of the hind body is densely set in the females with regularly arranged hairs, by means of which the pollen is carried. In many of the Dasygastres (_Megachile_, _e.g._) the labrum is very large, and in repose is inflected on to the lower side of the head, and closely applied to the doubled-in tongue, which it serves to protect; the mandibles then lock together outside the labrum, which is thus completely concealed. This group includes some of the most interesting of the solitary bees.

[Illustration: Fig. 18.—_Euglossa cordata_, ♂. Amazons. A, The Insect with extended proboscis; B, outer face of hind tibia and tarsus.]

The genus _Chalicodoma_ is not found in our own country, but in the South of France there exist three or four species. Their habits have given rise to much discussion, having been described by various naturalists, among whom are included Réaumur and Fabre. These Insects are called mason-bees, and construct nests of very solid masonry. _C. muraria_ is in appearance somewhat intermediate between a honey-bee and a _Bombus_; it is densely hairy, and the sexes are very different in colour. It is solitary in its habits, and usually chooses a large stone as a solid basis for its habitation. On this a cell is formed, the material used being a kind of cement made by the Insect from the mixture of a {36}suitable sort of earth with the material secreted by its own salivary glands; the amount of cement used is reduced by the artifice of building small stones into the walls of the cell; the stones are selected with great care. When a cell about an inch in depth has been formed in this manner, the bee commences to fill it with food, consisting of honey and pollen; a little honey is brought and is discharged into the cell, then some pollen is added. This bee, like other Dasygastres, carries the pollen by means of hairs on the under surface of the body; to place this pollen in the cell the Insect therefore enters backwards, and then with the pair of hind legs brushes and scrapes the under surface of the body so as to make the pollen fall off into the cell; it then starts for a fresh cargo; after a few loads have been placed in the receptacle, the Insect mixes the honey and pollen into a paste with the mandibles, and again continues its foraging until it has about half filled the cell; then an egg is laid, and the apartment is at once closed with cement. This work is all accomplished, if the weather be favourable, in about two days, after which the Insect commences the formation of a second cell, joined to the first, and so on till eight or nine of these receptacles have been constructed; then comes the final operation of adding an additional protection in the shape of a thick layer of mortar placed over the whole; the construction, when thus completed, forms a sort of dome of cement about the size of half an orange. In this receptacle the larvae pass many months, exposed to the extreme heat of summer as well as to the cold of winter. The larvae, however, are exposed to numerous other perils; and we have already related (vol. v. p. 540) how _Leucospis gigas_ succeeds in perforating the masonry and depositing therein an egg, so that a _Leucospis_ is reared in the cell instead of a _Chalicodoma_.

[Illustration: Fig. 19—_Chalicodoma muraria_. Greece. A, Male; B, female.]

{37}This Insect has been the object of some of J. H. Fabre's most instructive studies on instinct.[28] Although it is impossible for us here to consider in a thorough manner the various points he has discussed, yet some of them are of such interest and importance as to demand something more than a passing allusion.

We have mentioned that the nest of _Chalicodoma_ is roofed with a layer of solid cement in addition to the first covering with which the bee seals up each cell. When the metamorphoses of the imprisoned larva have been passed through, and the moment for its emergence as a perfect Insect has arrived, the prisoner has to make its way through the solid wall by which it is encompassed. Usually it finds no difficulty in accomplishing the task of breaking through the roof, so that the powers of its mandibles must be very great. Réaumur has, however, recorded that a nest of this mason-bee was placed under a glass funnel, the orifice of which was covered with gauze, and that the Insects when they emerged from the nest were unable to make their way through the gauze, and consequently perished under the glass cover; and he concluded that such insects are only able to accomplish the tasks that naturally fall to their lot. By some fresh experiments Fabre, however, has put the facts in a different light. He remarks that when the Insects have, in the ordinary course of emergence, perforated the walls of their dark prison, they find themselves in the daylight, and at liberty to walk away; when they have made their escape from a nest placed under a glass cover, they, having no knowledge of glass, find themselves in daylight and imprisoned by the glass, which, to their inexperience, does not appear to be an obstacle, and they therefore, he thought, might perhaps exhaust themselves in vain efforts to pass through this invisible obstacle. He therefore took some cocoons containing pupae from a nest, placed each one of them in a tube of reed, and stopped the ends of the reeds with various substances, in one case earth, in another pith, in a third brown paper; the reeds were then so arranged that the Insects in them were in a natural position; in due course all the Insects emerged, none of them apparently having found the novel nature of the obstacle a serious impediment. Some complete nests were then taken with their inmates, and to the exterior of one of them a sheet of opaque paper was closely fastened, while to another the same {38}sort of paper was applied in the form of a dome, leaving thus a considerable space between the true cover of the nest and the covering of paper. From the first nest the Insects made their escape in the usual manner, thus again proving that paper can be easily pierced by them. From the second nest they also liberated themselves, but failed to make their way out through the dome of paper, and perished beneath it; thus showing that paper added to the natural wall caused them no difficulty, but that paper separated therefrom by a space was an insuperable obstacle. Professor Pérez has pointed out that this is no doubt due to the large space offered to the bee, which consequently moves about, and does not concentrate its efforts on a single spot, as it of course is compelled to do when confined in its natural cell.

The power of the mason-bee to find its nest again when removed to a distance from it is another point that was tested by Du Hamel and recounted by Réaumur. As regards this Fabre has also made some very valuable observations. He marked some specimens of the bee, and under cover removed them to a distance of four kilometres, and then liberated them; the result proved that the bees easily found their way back again, and indeed were so little discomposed by the removal that they reached their nests laden with pollen as if they had merely been out on an ordinary journey. On one of these occasions he observed that a _Chalicodoma_, on returning, found that another bee had during her absence taken possession of her partially completed cell, and was unwilling to relinquish it; whereupon a battle between the two took place. The account of this is specially interesting, because it would appear that the two combatants did not seek to injure one another, but were merely engaged in testing, as it were, which was the more serious in its claims to the proprietorship of the cell in dispute. The matter ended by the original constructor regaining and retaining possession. Fabre says that in the case of _Chalicodoma_ it is quite a common thing for an uncompleted cell to be thus appropriated by a stranger during the absence of the rightful owner, and that after a scene of the kind described above, the latter of the two claimants always regains possession, thus leading one to suppose that some sense of rightful ownership exists in these bees; the usurper expressing, as it were, by its

## actions the idea—Before I {39}resign my claims I must require you to go

through the exertions that will prove you to be really the lawful owner.

Another experiment was made with forty specimens of _Chalicodoma pyrenaica_, which were removed to a distance of four kilometres and then liberated. About twenty of the individuals had been somewhat injured by the processes of capturing, marking, and transferring, and proved unable to make a proper start. The others went off well when released, and in forty minutes the arrivals at the nest had already commenced. The next morning he was able to ascertain that fifteen at least had found their way back, and that it was probable that most of the uninjured bees had reached home; and this although, as Fabre believed, they had never before seen the spot where he liberated them.

These observations on the power of _Chalicodoma_ to regain its nest attracted the attention of Charles Darwin, who wrote to M. Fabre, and suggested that further observations should be made with the view of ascertaining by means of what sense these bees were able to accomplish their return. For it must be borne in mind that this bee is very different from the domestic bee, inasmuch as it enjoys but a brief life in the winged state, and it is therefore to be presumed that an individual has no knowledge of such comparatively distant localities as those to which Fabre transported it. Further observations made by the Frenchman have unfortunately failed to throw any light on this point. Darwin thought it might possibly be some sensitiveness to magnetic conditions that enabled the bees to return home, and suggested that they should be tested as to this. Fabre accordingly made some minute magnets, and fixed one to each bee previous to letting them loose for a return journey. This had the effect of completely deranging the bees; and it was therefore at first thought that the requisite clue was obtained. It occurred to the experimenter, however, to try the plan of affixing small pieces of straw to the bees instead of magnets, and on this being done it was found that the little creatures were just as much deranged by the straws as they were by the magnets: thus it became evident that no good grounds exist for considering that the bees are guided by magnetic influences.

One of the species[29] of _Chalicodoma_ observed by Fabre fixes {40}its nests to the small boulders brought down and left by the Rhone on the waste places of its banks. This habit afforded Fabre an opportunity of removing the nests during the process of construction, and of observing the effect this produced on the architects. While a bee that had a nest partially constructed was absent, he removed the stone and the nest attached to it from one situation to another near at hand and visible from the original site. In a few minutes the bee returned and went straight to the spot where the nest had been; finding its home absent it hovered for a little while around the place, and then alighted on the vacated position, and walked about thereon in search of the nest; being after some time convinced that this was no longer there, it took wing, but speedily returned again to the place and went through the same operations. This series of manoeuvres was several times repeated, the return always being made to the exact spot where the nest had been originally located; and although the bee in the course of its journeys would pass over the nest at a distance of perhaps only a few inches, it did not recognise the object it was in search of. If the nest were placed very near to the spot it had been removed from—say at a distance of about a yard—it might happen that the bee would actually come to the stone to which the nest was fixed, would visit the nest, would even enter into the cell it had left partially completed, would examine circumspectly the boulder, but would always leave it, and again return to the spot where the nest was originally situated, and, on finding that the nest was not there, would take its departure altogether from the locality. The home must be, for the bee, in the proper situation, or it is not recognised as the desired object. Thus we are confronted with the strange fact that the very bee that is able to return to its nest from a distance of four kilometres can no longer recognise it when removed only a yard from the original position. This extraordinary condition of the memory of the Insect is almost inconceivable by us. That the bee should accurately recognise the spot, but that it should not recognise the cell it had itself just formed and half-filled with honey-paste, seems to us almost incredible; nevertheless, the fact is quite consistent with what we shall subsequently relate in the case of the solitary wasp _Bembex_. A cross experiment was made by taking away the stone with the attached nest of the bee while the latter {41}was absent, and putting in its place the nest of another individual in about the same stage of construction; this nest was at once adopted by the bee, which indeed was apparently in no way deranged by the fact that the edifice was the work of another. A further experiment was made by transposing the positions of two nests that were very near together, so that each bee when returning might be supposed to have a free choice as to which nest it would go to. Unhesitatingly each bee selected the nest that, though not its own, was in the position where its own had been. This series of experiments seems to prove that the _Chalcidoma_ has very little sense as to what is its own property, but, on the other hand, has a most keen appreciation of locality. As, however, it might be supposed that the bees were deceived by the similarity between the substituted nests, Fabre transposed two nests that were extremely different, one consisting of many cells, the other of a single incomplete cell; it was, of course, a necessary condition of this experiment that each of the two nests, however different in other respects, should possess one cell each in similar stages of construction; and when that was the case each bee cheerfully adopted the nest that, though very different to its own, was in the right place. This transposition of nests can be rapidly repeated, and thus the same bee may be made to go on working at two different nests.

Suppose, however, that another sort of change be made. Let a nest, consisting of a cell that is in an early stage of construction, be taken away, and let there be substituted for it a cell built and partially stored with food. It might be supposed that the bee would gladly welcome this change, for the adoption of the substituted cell would save it a great deal of work. Not so, however; the bee in such a case will take to the substituted cell, but will go on building at it although it is already of the full height, and will continue building at it until the cell is made as much as a third more than the regulation height. In fact the bee, being in the building stage of its operations, goes on building, although in so doing it is carrying on a useless, if not an injurious, work. A similar state ensues when the Insect ceases to build and begins to bring provisions to the nest; although a substituted cell may contain a sufficient store of food, the bee goes on adding to this, though it is wasting its labours in so doing. It should be noted that though the bee must go through the {42}appropriate stages of its labours whether the result of so doing be beneficial or injurious, yet it is nevertheless to some extent controlled by the circumstances, for it does not in such cases complete what should have been the full measure of its own individual work; it does not, for instance, raise the cell to twice the natural height, but stops building when the cell is about one-third larger than usual, as if at that stage the absurdity of the situation became manifest to it.

Fabre's experiments with the _Chalicodoma_ are so extremely instructive as regards the nature of instinct in some of the highest Insects, that we must briefly allude to some other of his observations even at the risk of wearying the reader who feels but little interest in the subject of Insect intelligence.

Having discovered that a mason-bee that was engaged in the process of construction would go on building to an useless or even injurious extent, Fabre tried another experiment to ascertain whether a bee that was engaged in the process of provisioning the nest, would do so in conditions that rendered its work futile. Taking away a nest with completely built cell that a bee was storing with food, he substituted for it one in which the cell was only commenced, and therefore incapable of containing food; when the bee with its store of provisions reached this should-be receptacle it appeared to be very perplexed, tested the imperfect cell with its antennae, left the spot and returned again; repeating this several times it finally went to the cell of some stranger to deposit its treasure. In other cases the bee broke open a completed cell, and having done so went on bringing provisions to it, although it was already fully provisioned and an egg laid therein: finally, the little creature having completed the bringing of this superfluous tale of provisions, deposited a second egg, and again sealed up the cell. But in no case does the bee go back from the provisioning stage to the building stage until the cycle for one cell of building, provisioning, and egg-laying is completed: but when this is the case, the building of a fresh cell may be again undertaken. This is a good example of the kind of consecutive necessity that seems to be one of the chief features of the instinct of these industrious little animals. Another equally striking illustration of these peculiarities of instinct is offered by interfering with the act of putting the provisions into the cell. It will be recollected that {43}when the bee brings provisions to add to the stock, it carries both honey and pollen; in order to deliver these it begins by entering head first into the cell and disgorging the honey, then emerging it turns round, enters backwards and scrapes off the pollen from its body. If after the honey has been discharged, the bee be interfered with and gently removed to a slight distance with a straw, it returns to complete its task, but instead of going on with the actions at the point at which the interruption took place, it begins the series over again, going in—at any rate partially—head first, although it has no honey to discharge, and having performed this useless ceremony it then emerges, turns round and adds the pollen. This illustration is in some respects the reverse of what might have been expected, for the Insect here does not continue the act at the interrupted point, but begins the series of actions afresh.

It would be reasonable to suppose that an Insect that takes the pains to provide for the safety of its progeny by constructing a complex edifice of cement, secures thereby the advantage of protection for its young. But this is far from being the case. Notwithstanding the cement and the thick dome of mortar, the _Chalicodoma_ is extremely subject to the attacks of parasites. The work performed by the creature in constructing its mass of masonry is truly astounding; Fabre calculated from measurements he made that for the construction and provisioning of a single cell, the goings and comings of the bee amounted to 15 kilometres, and it makes for each nest sometimes as many as fifteen cells. Notwithstanding all this labour, it would appear that no real safety for the larvae is obtained by the work. Some sixteen—possibly more—other species of Insects get their living off this industrious creature. Another bee, _Stelis nasuta_, breaks open the cells after they have been completely closed and places its own eggs in them, and then again closes the cells with mortar. The larvae of this _Stelis_ develop more rapidly than do those of the _Chalicodoma_, so that the result of this shameless proceeding is that the young one of the legitimate proprietor—as we human beings think it—is starved to death, or is possibly eaten up as a dessert by the _Stelis_ larvae, after they have appropriated all the pudding.

Another bee, _Dioxys cincta_, is even more audacious; it flies about in a careless manner among the _Chalicodoma_ at their {44}work, and they do not seem to object to its presence unless it interferes with them in too unmannerly a fashion, when they brush it aside. The _Dioxys_, when the proprietor leaves the cell, will enter it and taste the contents; after having taken a few mouthfuls the impudent creature then deposits an egg in the cell, and, it is pretty certain, places it at or near the bottom of the mass of pollen, so that it is not conspicuously evident to the _Chalicodoma_ when the bee again returns to add to or complete the stock of provisions. Afterwards the constructor deposits its own egg in the cell and closes it. The final result is much the same as in the case of the _Stelis_, that is to say, the _Chalicodoma_ has provided food for an usurper; but it appears probable that the consummation is reached in a somewhat different manner, namely, by the _Dioxys_ larva eating the egg of the _Chalicodoma_, instead of slaughtering the larva. Two of the Hymenoptera Parasitica are very destructive to the _Chalicodoma_, viz. _Leucospis gigas_ and _Monodontomerus nitidus_; the habits of which we have already discussed (vol. v. p. 543) under Chalcididae. Lampert has given a list of the Insects attacking the mason-bee or found in its nests; altogether it would appear that about sixteen species have been recognised, most of which destroy the bee larva, though some possibly destroy the bee's destroyers, and two or three perhaps merely devour dead examples of the bee, or take the food from cells, the inhabitants of which have been destroyed by some untoward event. This author thinks that one half of the bees' progeny are made away with by these destroyers, while Fabre places the destruction in the South of France at a still higher ratio, telling us that in one nest of nine cells, the inhabitants of three were destroyed by the Dipterous Insect, _Anthrax trifasciata_, of two by _Leucospis_, of two by _Stelis_, and of one by the smaller Chalcid; there being thus only a single example of the bee that had not succumbed to one or other of the enemies. He has sometimes examined a large number of nests without finding a single one that had not been attacked by one or other of the parasites, and more often than not several of the marauders had attacked the nest.

It is said by Lampert and others that there is a passage in Pliny relating to one of the mason-bees, that the Roman author had noticed in the act of carrying off stones to build into its nest; being unacquainted with the special habits of the bee, he {45}seems to have supposed that the insect was carrying the stone as ballast to keep itself from being blown away.

[Illustration: Fig. 20—_Anthidium manicatum_, Carder-bee. A, Male; B, female.]

The bees of the genus _Anthidium_ are known to possess the habit of making nests of wool or cotton, that they obtain from plants growing at hand. We have one species of this genus of bees in Britain; it sometimes may be seen at work in the grounds of our Museum at Cambridge: it is referred to by Gilbert White, who says of it, in his _History of Selborne_: "There is a sort of wild bee frequenting the garden-campion for the sake of its tomentum, which probably it turns to some purpose in the business of nidification. It is very pleasant to see with what address it strips off the pubes, running from the top to the bottom of a branch, and shaving it bare with the dexterity of a hoop-shaver. When it has got a bundle, almost as large as itself, it flies away, holding it secure between its chin and its fore legs." The species of this genus are remarkable as forming a conspicuous exception to the rule that in bees the female is larger than the male. The species of _Anthidium_ do not form burrows for themselves, but either take advantage of suitable cavities formed by other Insects in wood, or take possession of deserted nests of other bees or even empty snail-shells. The workers in cotton, of which our British species _A. manicatum_ is one, line the selected receptacle with a beautiful network of cotton or wool, and inside this place a finer layer of the material, to which is added some sort of cement that prevents the honied mass stored by the bees in this receptacle from passing out of it. _A. diadema_, one of the species that form nests in hollow stems, has been specially observed by Fabre; it will take the cotton for {46}its work from any suitable plant growing near its nest, and does not confine itself to any particular natural order of plants, or even to those that are indigenous to the South of France. When it has brought a ball of cotton to the nest, the bee spreads out and arranges the material with its front legs and mandibles, and presses it down with its forehead on to the cotton previously deposited; in this way a tube of cotton is constructed inside the reed; when withdrawn, the tube proved to be composed of about ten distinct cells arranged in linear fashion, and connected firmly together by means of the outer layer of cotton; the transverse divisions between the chambers are also formed of cotton, and each chamber is stored with a mixture of honey and pollen. The series of chambers does not extend quite to the end of the reed, and in the unoccupied space the Insect accumulates small stones, little pieces of earth, fragments of wood or other similar small objects, so as to form a sort of barricade in the vestibule, and then closes the tube by a barrier of coarser cotton taken frequently from some other plant, the mullein by preference. This barricade would appear to be an ingenious attempt to keep out parasites, but if so, it is a failure, at any rate as against _Leucospis_, which insinuates its eggs through the sides, and frequently destroys to the last one the inhabitants of the fortress. Fabre states that these _Anthidium_, as well as _Megachile_, will continue to construct cells when they have no eggs to place in them; in such a case it would appear from his remarks that the cells are made in due form and the extremity of the reed closed, but no provisions are stored in the chambers.

The larva of the _Anthidium_ forms a most singular cocoon. We have already noticed the difficulty that arises, in the case of these Hymenopterous larvae shut up in small chambers, as to the disposal of the matters resulting from the incomplete assimilation of the aliment ingested. To allow the once-used food to mingle with that still remaining unconsumed would be not only disagreeable but possibly fatal to the life of the larva. Hence some species retain the whole of the excrement until the food is entirely consumed, it being, according to Adlerz, stored in a special pouch at the end of the stomach; other Hymenoptera, amongst which we may mention the species of _Osmia_, place the excreta in a vacant space. The _Anthidium_ adopts, however, a most remarkable system: about the middle of its {47}larval life it commences the expulsion of "frass" in the shape of small pellets, which it fastens together with silk, as they are voided, and suspends round the walls of the chamber. This curious arrangement not only results in keeping the embarrassing material from contact with the food and with the larva itself, but serves, when the growth of the latter is accomplished, as the outline or foundations of the cocoon in which the metamorphosis is completed. This cocoon is of a very elaborate character; it has, so says Fabre, a beautiful appearance, and is provided with a very peculiar structure in the form of a small conical protuberance at one extremity pierced by a canal. This canal is formed with great care by the larva, which from time to time places its head in the orifice in process of construction, and stretches the calibre by opening the mandibles. The object of this peculiarity in the fabrication of the elaborate cocoon is not clear, but Fabre inclines to the opinion that it is for respiratory purposes.

Other species of this genus use resin in place of cotton as their working material. Among these are _Anthidium septemdentatum_ and _A. bellicosum_. The former species chooses an old snail-shell as its nidus, and constructs in it near the top a barrier of resin, so as to shut off the part where the whorl is too small; then beneath the shelter of this barrier it accumulates a store of honey-pollen, deposits an egg, and completes the cell by another transverse barrier of resin; two such cells are usually constructed in one snail-shell, and below them is placed a barricade of small miscellaneous articles, similar to what we have described in speaking of the cotton-working species of the genus. This bee completes its metamorphosis, and is ready to leave the cell in early spring. Its congener, _A. bellicosum_, has the same habits, with the exception that it works later in the year, and is thus exposed to a great danger, that very frequently proves fatal to it. This bee does not completely occupy the snail-shell with its cells, but leaves the lower and larger portion of the shell vacant. Now, there is another bee, a species of _Osmia_, that is also fond of snail-shells as a nesting-place, and that affects the same localities as the _A. septemdentatum_; very often the _Osmia_ selects for its nest the vacant part of a shell, the other part of which is occupied by the _Anthidium_; the result of this is that when the metamorphoses are completed, the latter bee is unable to effect its escape, and {48}thus perishes in the cell. Fabre further states with regard to these interesting bees, that no structural differences of the feet or mandibles can be detected between the workers in cotton and the workers in resin; and he also says that in the case where two cells are constructed in one snail-shell, a male individual is produced from the cell of the greater capacity, and a female from the other.

_Osmia_ is one of the most important of the genera of bees found in Europe, and is remarkable for the diversity of instinct displayed in the formation of the nests of the various species. As a rule they avail themselves for nidification of hollow places already existing; choosing excavations in wood, in the mortar of walls, and even in sandbanks; in several cases the same species is found to be able to adapt itself to more than one kind of these very different substances. This variety of habit will render it impossible for us to do justice to this interesting genus within the space at our disposal, and we must content ourselves with a consideration of one or two of the more instructive of the traits of _Osmia_ life. _O. tridentata_ forms its nest in the stems of brambles, of which it excavates the pith; its mode of working and some other details of its life have been well depicted by Fabre. The Insect having selected a suitable bramble-stalk with a cut extremity, forms a cylindrical burrow in the pith thereof, extending the tunnel as far as will be required to allow the construction of ten or more cells placed one after the other in the axis of the cylinder; the bee does not at first clear out quite all the pith, but merely forms a tunnel through it, and then commences the construction of the first cell, which is placed at the end of the tunnel that is most remote from the entrance. This cavity is to be of oval form, and the Insect therefore cuts away more of the pith so as to make an oval space, but somewhat truncate, as it were, at each end, the plane of truncation at the proximal extremity being of course an orifice.

[Illustration: Fig. 21.—_Osmia tricornis_, ♀. Algeria.]

{49}The first cell thus made is stored with pollen and honey, and an egg is deposited. Then a barrier has to be constructed to close this chamber; the material used for the barrier is the pith of the stem, and the Insect cuts the material required for the purpose from the walls of the second chamber; the excavation of the second chamber is, in fact, made to furnish the material for closing up the first cell. In this way a chain of cells is constructed, their number being sometimes as many as fifteen. The mode in which the bees, when the transformations of the larvae and pupae have been completed, escape from the chain of cells, has been the subject of much discussion, and errors have arisen from inference being allowed to take the place of observation. Thus Dufour, who noted this same mode of construction and arrangement in another Hymenopteron (_Odynerus nidulator_), perceived that there was only one orifice of exit, and also that the Insect that was placed at the greatest distance from this was the one that, being the oldest of the series, might be expected to be the first ready to emerge; and as the other cocoons would necessarily be in the way of its getting out, he concluded that the egg that was last laid produced the first Insect ready for emergence. Fabre tested this by some ingenious experiments, and found that this was not the case, but that the Insects became ready to leave their place of imprisonment without any reference to the order in which the eggs were laid, and he further noticed some very curious facts with reference to the mode of emergence of _Osmia tridentata_. Each Insect, when it desires to leave the bramble stem, tears open the cocoon in which it is enclosed, and also bites through the barrier placed by the mother between it and the Insect that is next it, and that separates it from the orifice of exit. Of course, if it happen to be the outside one of the series it can then escape at once; but if it should be one farther down in the Indian file it will not touch the cocoon beyond, but waits patiently, possibly for days; if it then still find itself confined it endeavours to escape by squeezing past the cocoon that intervenes between it and liberty, and by biting away the material at the sides so as to enlarge the passage; it may succeed in doing this, and so get out, but if it fail to make a side passage it will not touch the cocoons that are in its way. In the ordinary course of events, supposing all to go well with the family, all the cocoons produce their inmates in a state for emergence within {50}a week or two, and so all get out. Frequently, however, the emergence is prevented by something having gone wrong with one of the outer Insects, in which case all beyond it perish unless they are strong enough to bite a hole through the sides of the bramble-stem. Thus it appears that whether a particular _Osmia_ shall be able to emerge or not depends on two things—(1) whether all goes well with all the other Insects between it and the orifice, and (2) whether the Insect can bite a lateral hole or not; this latter point also largely depends on the thickness of the outer part of the stem of the bramble. Fabre's experiments on these points have been repeated, and his results confirmed by Nicolas.

The fact that an _Osmia_ would itself perish rather than attack the cocoon of its brother or sister is certainly very remarkable, and it induced Fabre to make some further experiments. He took some cocoons containing dead specimens of _Osmia_, and placed them in the road of an _Osmia_ ready for exit, and found that in such case the bee made its way out by demolishing without any scruple the cocoons and dead larvae that intervened between it and liberty. He then took some other reeds, and blocked the way of exit with cocoons containing living larvae, but of another species of Hymenoptera. _Solenius vagus_ and _Osmia detrita_ were the species experimented on in this case, and he found that the _Osmia_ destroyed the cocoon and living larvae of the _Solenius_, and so made its way out. Thus it appears that _Osmia_ will respect the life of its own species, and die rather than destroy it, but has no similar respect for the life of another species.

Some of Fabre's most instructive chapters are devoted to the habits and instincts of various species of the genus _Osmia_. It is impossible here to find space even to summarise them, still more impossible to do them justice; but we have selected the history just recounted, because it is rare to find in the insect world instances of such self-sacrifice by an individual for one of the same generation. It would be quite improper to generalise from this case, however, and conclude that such respect for its own species is common even amongst the Osmia. Fabre, indeed, relates a case that offers a sad contrast to the scene of self-sacrifice and respect for the rights of others that we have roughly portrayed. He was able to induce a colony of _Osmia tricornis_ (another species of the genus, be it noted) to establish itself and {51}work in a series of glass tubes that he placed on a table in his laboratory. He marked various individuals, so that he was able to recognise them and note the progress of their industrial works. Quite a large number of specimens thus established themselves and concluded their work before his very eyes. Some individuals, however, when they had completed the formation of a series of cells in a glass tube or in a reed, had still not entirely completed their tale of work. It would be supposed that in such a case the individual would commence the formation of another series of cells in an unoccupied tube. This was not, however, the case. The bee preferred tearing open one or more cells already completed—in some cases, even by itself—scattering the contents, and devouring the egg; then again provisioning the cell, it would deposit a fresh egg, and close the chamber. These brief remarks will perhaps suffice to give some idea of the variety of instinct and habit that prevails in this very interesting genus. Friese observes that the variety of habits in this genus is accompanied as a rule by paucity of individuals of a species, so that in central Europe a collector must be prepared to give some twenty years or so of attention to the genus before he can consider he has obtained all the species of _Osmia_ that inhabit his district.

As a prelude to the remarks we are about to make on the leaf-cutting bees of the genus _Megachile_ it is well to state that the bee, the habits of which were described by Réaumur under the name of "l'abeille tapissière," and that uses portions of the leaves of the scarlet poppy to line its nest, is now assigned to the genus _Osmia_, although Latreille, in the interval that has elapsed since the publication of Réaumur's work, founded the genus _Anthocopa_ for the bee in question. _Megachile_ is one of the most important of the genera of the Dasygastres, being found in most parts of the world, even in the Sandwich Islands; it consists of bees averaging about the size of the honey-bee (though some are considerably larger, others smaller), and having the labrum largely developed; this organ is capable of complete inflection to the under side of the head, and when in the condition of repose it is thus infolded, it underlaps and protects the larger part of the lower lip; the mandibles close over the infolded labrum, so that, when the Insect is at rest, this appears to be altogether absent. These bees are called leaf-cutters, from their habit of forming the cells for their nest {52}out of pieces of the leaves of plants. We have several species in Britain; they are very like the common honey-bee in general appearance, though rather more robustly formed. These Insects, like the Osmiae, avail themselves of existing hollow places as receptacles in which to place their nests. _M. albocincta_ frequently takes possession of a deserted worm-burrow in the ground. The burrow being longer than necessary the bee commences by cutting off the more distant part by means of a barricade of foliage; this being done, it proceeds to form a series of cells, each shaped like a thimble with a lid at the open end (Fig. 22, A). The body of the thimble is formed of large oval pieces of leaf, the lid of smaller round pieces; the fragments are cut with great skill from the leaves of growing plants by the Insect, which seems to have an idea of the form and size of the piece of foliage necessary for each particular stage of its work.

[Illustration: Fig. 22—Nidification of leaf-cutting bee, _Megachile anthracina_. A, one cell separated, with lid open; the larva (_a_) reposing on the food; B, part of a string of the cells. (After Horne.)]

Horne has given particulars as to the nest of _Megachile anthracina_ (_fasciculata_), an East Indian species.[30] The material employed was either the leaves of the Indian pulse or of the rose. Long pieces are cut by the Insect from the leaf, and with these a cell is formed; a circular piece is next cut, and with this a lid is made for the receptacle. The cells are about the size and shape of a common thimble; in one specimen that Horne examined no less than thirty-two pieces of leaf disposed in seven layers were used for one cell, in addition to three pieces for the round top. The cells are carefully prepared, and some kind of matter of a gummy nature is believed to be used to keep in place the pieces forming the interior layers. The cells are placed end to end, as shown in Fig. 22, B; five to seven cells form a series, and four or six series are believed to be constructed by one pair {53}of this bee, the mass being located in a hollow in masonry or some similar position. Each cell when completed is half filled with pollen in the usual manner, and an egg is then laid in it. This bee is much infested by parasites, and is eaten by the Grey Hornbill (_Meniceros bicornis_).

_Megachile lanata_ is one of the Hymenoptera that in East India enter houses to build their own habitations. According to Horne both sexes take

## part in the work of construction, and the spots chosen are frequently of a

very odd nature. The material used is some kind of clay, and the natural situation may be considered to be the interior of a hollow tube, such as the stem of a bamboo; but the barrel of a gun, and the hollow in the back of a book that has been left lying open, have been occasionally selected by the Insect as suitable. Smith states that the individuals developed in the lower part of a tubular series of this species were females, "which sex takes longer to develop, and thus an exit is not required for them so soon as for the occupants of the upper cells which are males." _M. proxima_, a species almost exactly similar in appearance to _M. lanata_, makes its cells of leaf-cuttings, however, and places them in soft soil.

Fabre states that _M. albocincta_, which commences the formation of its nest in a worm-burrow by means of a barricade, frequently makes the barricade, but no nest; sometimes it will indeed make the barricade more than twice the proper size, and thus completely fill up the worm burrow. Fabre considers that these eccentric proceedings are due to individuals that have already formed proper nests elsewhere, and that after completing these have still some strength remaining, which they use up in this fruitless manner.

The SOCIAL BEES (Sociales) include, so far as is yet known, only a very small number of genera, and are so diverse, both in habits and structure, that the propriety of associating them in one group is more than doubtful; the genera are _Bombus_ (Fig. 331, vol. v.), with its commensal genus or section, _Psithyrus_ (Fig. 23); _Melipona_ (Fig. 24), in which _Trigona_ and _Tetragona_ may at present be included, and _Apis_ (Fig. 6); this latter genus comprising the various honey-bees that are more or less completely domesticated in different parts of the world.

In the genus _Bombus_ the phenomena connected with the social life are more similar to what we find among wasps {54}than to what they are in the genus _Apis_. The societies come to an end at the close of the season, a few females live through the winter, and each of these starts a new colony in the following spring. Males, females and workers exist, but the latter are not distinguished by any good characters from the females, and are, in fact, nothing but more or less imperfect forms thereof; whereas in _Apis_ the workers are distinguished by structural characters not found in either of the true sexes.

Hoffer has given a description of the commencement of a society of _Bombus lapidarius_.[31] A large female, at the end of May, collected together a small mass of moss, then made an expedition and returned laden with pollen; under cover of the moss a cell was formed of wax taken from the hind-body and mixed with the pollen the bee had brought in; this cell was fastened to a piece of wood; when completed it formed a subspherical receptacle, the outer wall of which consisted of wax, and whose interior was lined with honey-saturated pollen; then several eggs were laid in this receptacle, and it was entirely closed. Hoffer took the completed cell away to use it for museum purposes, and the following day the poor bee that had formed it died. From observations made on _Bombus agrorum_ he was able to describe the subsequent operations; these are somewhat as follows:—The first cell being constructed, stored, and closed, the industrious architect, clinging to the cell, takes a few days' rest, and after this interval commences the formation of a second cell; this is placed by the side of the first, to which it is connected by a mixture of wax and pollen; the second cell being completed a third may be formed; but the labours of the constructor about this time are augmented by the hatching of the eggs deposited a few days previously; for the young larvae, having soon disposed of the small quantity of food in the interior of the waxen cell, require feeding. This operation is carried on by forming a small opening in the upper part of the cell, through which the bee conveys food to the interior by ejecting it from her mouth through the hole; whether the food is conveyed directly to the mouths of the larvae or not, Hoffer was unable to observe; it being much more difficult to approach this royal founder without disturbing her than it is the worker-bees that carry on similar occupations at a subsequent period in the history of the {55}society. The larvae in the first cell, as they increase in size, apparently distend the cell in an irregular manner, so that it becomes a knobbed and rugged, truffle-like mass. The same thing happens with the other cells formed by the queen. Each of these larval masses contains, it should be noticed, sister-larvae all of one age; when full grown they pupate in the mass, and it is worthy of remark that although all the eggs in one larval mass were laid at the same time, yet the larvae do not all pupate simultaneously, neither do all the perfect Insects appear at once, even if all are of one sex. The pupation takes place in a cocoon that each larva forms for itself of excessively fine silk. The first broods hatched are formed chiefly, if not entirely, of workers, but small females may be produced before the end of the season. Huber and Schmiedeknecht state that though the queen provides the worker-cells with food before the eggs are placed therein, yet no food is put in the cells in which males and females are produced. The queen, at the time of pupation of the larvae, scrapes away the wax by which the cocoons are covered, thus facilitating the escape of the perfect Insect, and, it may also be, aiding the access of air to the pupa. The colony at first grows very slowly, as the queen can, unaided, feed only a small number of larvae. But after she receives the assistance of the first batch of workers much more rapid progress is made, the queen greatly restricting her labours, and occupying herself with the laying of eggs; a process that now proceeds more and more rapidly, the queen in some cases scarcely ever leaving the nest, and in others even becoming incapable of flight. The females produced during the intermediate period of the colony are smaller than the mother, but supplement her in the process of egg-laying, as also do the workers to a greater or less extent. The conditions that determine the egg-laying powers of these small females and workers are apparently unknown, but it is ascertained that these powers vary greatly in different cases, so that if the true queen die the continuation of the colony is sometimes effectively carried on by these her former subordinates. In other cases, however, the reverse happens, and none of the inhabitants may be capable of producing eggs: in this event two conditions may be present; either larvae may exist in the nest, or they may be absent. In the former case the workers provide them with food, and the {56}colony may thus still be continued; but in the latter case, there being no profitable occupation for the bees to follow, they spend the greater part of the time sitting at home in the nest.

Supposing all to go well with the colony it increases very greatly, but its prosperity is checked in the autumn; at this period large numbers of males are produced as well as new queens, and thereafter the colony comes to an end, only a few fertilised females surviving the winter, each one to commence for herself a new colony in the ensuing spring.

The interior of the nest of a bumble-bee (_Bombus_) frequently presents a very irregular appearance; this is largely owing to the fact that these bees do not use the cells as cradles twice, but form others as they may be required, on the old remains. The cells, moreover, are of different sizes, those that produce workers being the smallest, those that cradle females being the largest, while those in which males are reared are intermediate in size. Although the old cells are not used a second time for rearing brood they are nevertheless frequently adapted to the purposes of receptacles for pollen and for honey, and for these objects they may be increased in size and altered in form.

It may be gathered from various records that the period required to complete the development of the individual _Bombus_ about midsummer is four weeks from the deposition of the egg to the emergence of the perfect Insect, but exact details and information as to whether this period varies with the sex of the Insect developed are not to be found. The records do not afford any reason for supposing that such distinction will be found to exist: the size of the cells appears the only correlation, suggested by the facts yet known, between the sex of the individual and the circumstances of development.

The colonies of _Bombus_ vary greatly in prosperity, if we take as the test of this the number of individuals produced in a colony. They never, however, attain anything at all approaching to the vast number of individuals that compose a large colony of wasps, or that exist in the crowded societies of the more perfectly social bees. A populous colony of a subterranean _Bombus_ may attain the number of 300 or 400 individuals. Those that dwell on the surface are as a rule much less populous, as they are less protected, so that changes of weather are more {57}prejudicial to them. According to Smith, the average number of a colony of _B. muscorum_ in the autumn in this country is about 120—viz. 25 females, 36 males, 59 workers. No mode of increasing the nests in a systematic manner exists in this genus; they do not place the cells in stories as the wasps do; and this is the case notwithstanding the fact that a cell is not twice used for the rearing of young. When the ground-space available for cell-building is filled the _Bombus_ begins another series of cells on the ruins of the first one. From this reason old nests have a very irregular appearance, and this condition of seeming disorder is greatly increased by the very different sizes of the cells themselves. We have already alluded to some of these cells, more particularly to those of different capacities to suit the sexes of the individuals to be reared in them. In addition to these there are honey-tubs, pollen-tubs, and the cells of the _Psithyrus_ (Fig. 23), the parasitic but friendly inmates of the _Bombus_-nests. A nest of _Bombus_, exhibiting the various pots projecting from the remains of empty and partially destroyed cells, presents, as may well be imagined, a very curious appearance. Some of the old cells apparently are partly destroyed for the sake of the material they are composed of. Others are formed into honey-tubs, of a make-shift nature. It must be recollected that, as a colony increases, stores of provisions become absolutely necessary, otherwise in bad weather the larvae could not be fed. In good weather, and when flowers abound, these bees collect and store honey in abundance; in addition to placing it in the empty pupa-cells, they also form for it special receptacles; these are delicate cells made entirely of wax filled with honey, and are always left open for the benefit of the community. The existence of these honey-tubs in bumble-bees' nests has become known to our country urchins, whose love for honey and for the sport of bee-baiting leads to wholesale destruction of the nests. According to Hoffer, special tubs for the storing of pollen are sometimes formed; these are much taller than the other cells. The _Psithyrus_ that live in the nests with the _Bombus_ are generally somewhat larger than the latter, and consequently their cells may be distinguished in the nests by their larger size. A bumble-bees' nest, composed of all these heterogenous chambers rising out of the ruins of former layers of cells, presents a scene of such apparent disorder that {58}many have declared that the bumble-bees do not know how to build.

Although the species of _Bombus_ are not comparable with the hive-bee in respect of the perfection and intelligent nature of their work, yet they are very industrious Insects, and the construction of the dwelling-places of the subterranean species is said to be carried out in some cases with considerable skill, a dome of wax being formed as a sort of roof over the brood cells. Some work even at night. Fea has recorded the capture of a species in Upper Burmah working by moonlight, and the same industry may be observed in this country if there be sufficient heat as well as light. Godart, about 200 years ago, stated that a trumpeter-bee is kept in some nests to rouse the denizens to work in the morning: this has been treated as a fable by subsequent writers, but is confirmed in a circumstantial manner by Hoffer, who observed the performance in a nest of _B. ruderatus_ in his laboratory. On the trumpeter being taken away its office was the following morning filled by another individual The trumpeting was done as early as three or four o'clock in the morning, and it is by no means impossible that the earliness of the hour may have had something to do with the fact that for 200 years no one confirmed the old naturalist's observation.

One of the most curious facts in connection with _Bombus_ is the excessive variation that many of the species display in the colour of the beautiful hair with which they are so abundantly provided. There is not only usually a difference between the sexes in this respect, but also extreme variation within the limits of the same sex, more especially in the case of the males and workers; there is also an astonishing difference in the size of individuals. These variations are carried to such an extent that it is almost impossible to discriminate all the varieties of a species by inspection of the superficial characters. The structures peculiar to the male, as well as the sting of the female, enable the species to be determined with tolerable certainty. Cholodkovsky,[32] on whose authority this statement as to the sting is made, has not examined it in the workers, so that we do not know whether it is as invariable in them as he states it to be in queens of the same species. According to Handlirsch,[33] each {59}species of _Bombus_ has the capacity of variation, and many of the varieties are found in one nest, that is, among the offspring of a single pair of the species, but many of the variations are restricted to certain localities. Some of the forms can be considered as actual ("fertige") species, intermediate forms not being found, and even the characters by which species are recognised being somewhat modified. As examples of this he mentions _Bombus silvarum_ and _B. arenicola_, _B. pratorum_ and _B. scrimshiranus_. In other cases, however, the varieties are not so discontinuous, intermediate forms being numerous; this condition is more common than the one we have previously described; _B. terrestris_, _B. hortorum_, _B. lapidarius_ and _B. pomorum_ are examples of these variable species. The variation runs to a considerable extent in parallel lines in the different species, there being a dark and a light form of each; also each species that has a white termination to the body appears in a form with a red termination, and _vice versa_. In the Caucasus many species that have everywhere else yellow bands possess them white; and in Corsica there are species that are entirely black, with a red termination to the body, though in continental Europe the same species exhibit yellow bands and a white termination to the body. With so much variation it will be readily believed that much remains to be done in the study of this fascinating genus. It is rich in species in the Northern hemisphere, but poor in the Southern one, and in both the Ethiopian and Australian regions it is thought to be entirely wanting.

The species of the genus _Psithyrus_ (_Apathus_ of many authors) inhabit the nests of _Bombus_; although less numerous than the species of the latter genus, they also are widely distributed. They are so like _Bombus_ in appearance that they were not distinguished from them by the earlier entomologists; and what is still more remarkable, each species of _Psithyrus_ resembles the _Bombus_ with which it usually lives. There appear, however, to be occasional exceptions to this rule, Smith having seen one of the yellow-banded _Psithyrus_ in the nest of a red-tailed _Bombus_. _Psithyrus_ is chiefly distinguished from _Bombus_ by the absence of certain characters that fit the latter Insects for their industrial life; the hind tibiae have no smooth space for the conveyance of pollen, and, so far as is known, there are only two sexes, males and perfect females.

{60}[Illustration: Fig. 23—_Psithyrus vestalis_, Britain. A, Female, x 3/2; B, outer side of hind leg.]

The _Bombus_ and _Psithyrus_ live together on the best terms, and it appears probable that the latter do the former no harm beyond appropriating a portion of their food supplies. Schmiedeknecht says they are commensals, not parasites; but it must be admitted that singularly few descriptions of the habits and life-histories of these interesting Insects have been recorded. Hoffer has, however, made a few direct observations which confirm, and at the same time make more definite, the vague ideas that have been generally prevalent among entomologists. He found and took home a nest of _Bombus variabilis_, which contained also a female of _Psithyrus campestris_, so that he was able to make observations on the two. The _Psithyrus_ was much less industrious than the _Bombus_, and only left the nest somewhat before noon, returning home again towards evening; after about a month this specimen became still more inactive, and passed entire days in the nest, occupying itself in consuming the stores of honey of its hosts, of which very large quantities were absorbed, the _Psithyrus_ being much larger than the host-bee. The cells in which the young of the _Psithyrus_ are hatched are very much larger than those of the _Bombus_, and, it may therefore be presumed, are formed by the _Psithyrus_ itself, for it can scarcely be supposed that the _Bombus_ carries its complaisance so far as to construct a cell specially adapted to the superior stature of its uninvited boarder. When a _Psithyrus_ has been for some time a regular inhabitant of a nest, the _Bombus_ take its return home from time to time as a matter of course, displaying no emotion whatever at its entry. Occasionally Hoffer tried the introduction of a _Psithyrus_ to a nest that had not previously had one as an inmate. The new arrival caused a great hubbub among the _Bombus_, which rushed to it as if to attack it, but did not do so, and the alarm soon subsided, the _Psithyrus_ taking up the position in the nest usually affected by the individuals of the species. On {61}introducing a female _Psithyrus_ to a nest of _Bombus_ in which a _Psithyrus_ was already present as an established guest, the latter asserted its rights and drove away the new comer. Hoffer also tried the experiment of placing a _Psithyrus campestris_ in the nest of _Bombus lapidarius_—a species to which it was a stranger; notwithstanding its haste to fly away, it was at once attacked by the _Bombus_, who pulled it about but did not attempt to sting it.

When _Psithyrus_ is present in a nest of _Bombus_ it apparently affects the inhabitants only by diminishing their stores of food to so great an extent that the colony remains small instead of largely increasing in numbers. Although _Bombus variabilis_, when left to itself, increases the number of individuals in a colony to 200 or more, Hoffer found in a nest in which _Psithyrus_ was present, that on the 1st of September the assemblage consisted only of a queen _Bombus_ and fifteen workers, together with eighteen specimens of the _Psithyrus_, eight of these being females.

The nests of _Bombus_ are destroyed by several animals, probably for the sake of the honey contained in the pots; various kinds of small mammals, such as mice, the weasel, and even the fox, are known to destroy them; and quite a fauna of Insects may be found in them; the relations of these to their hosts are very little known, but some undoubtedly destroy the bees' larvae, as in the case of _Meloe_, _Mutilla_ and _Conops_. Birds do not as a rule attack these bees, though the bee-eater, _Merops apiaster_, has been known to feed on them very heavily.

The genera of social bees known as _Melipona_, _Trigona_ or _Tetragona_, may, according to recent authorities, be all included in one genus, _Melipona_. Some of these Insects are amongst the smallest of bees, so that one, or more, species go by the name of "Mosquito-bees." The species appear to be numerous, and occur in most of the tropical parts of the continents of the world, but unfortunately very little is known as to their life-histories or economics; they are said to form communities consisting at times of a countless number of individuals; but it has not been thoroughly ascertained whether these are the produce of a single queen, as in the case of the hive-bee, or whether there may be more than one egg-producer in each community. The late F. Smith thought the former of these alternatives would prove to be correct. These mosquito-bees are frequently spoken of as stingless bees, but this is not quite correct, for although they do not sting, {62}von Ihering[34] says that all the essential elements of the sting are present, the pointed or penetrating part of the apparatus being stunted.

It would serve no useful purpose to attempt to construct the social history of these stingless bees from the numerous brief scattered accounts in entomological literature, for they refer to different species; it is, however, positively stated by Smith on the authority of Peckolt[35] that _Trigona mosquito_ sends off swarms after the manner of the hive-bee in this country, and that after searching six hives only one royal female could be found in each.

[Illustration: Fig. 24.—_Melipona_ sp. ♀. Amazons.]

The nests of many of these little bees are rich in honey, and they have a host of enemies from man and monkeys downwards; and as they do not defend themselves by stinging, it might be supposed they would have but a poor time of it. From the accounts that have been published we may, however, gather that they are rich in devices for the protection of their nests, and for the exclusion of intruders. Bates has given some particulars as to _Melipona interrupta_ (_fasciculata_); it is about one-third shorter than the hive-bee, and its colonies are composed of an immense number of individuals. The workers are usually occupied in gathering pollen; but they also collect clay in a similar manner, and convey it to the nest, where it is used for building a wall to complete the fortification of the nest, which is placed either in a suitable bank, or in a trunk of a tree; in either situation it is completely built in with clay. A nest which Bates saw opened contained about two quarts of pleasantly-tasted liquid honey. Forty-five species of these little bees were found in different parts of the Amazons Valley, the largest kind being half an inch in length, the smallest very minute, not more than one-twelfth of an inch. These little creatures are thus masons as well as workers in wax and resin, and they are also gatherers of nectar, pollen, and resin.

{63}According to Gosse, one of these bees is well known in Jamaica, where they are called "Angelitos," in consequence of their not stinging people. He observed a nest of this bee in a tree, and found it to be much infested by black ants anxious to obtain entrance to it; three bees, however, stood sentinel in the entrance, so as to completely block it and keep out intruders, but the middle bee moved on one side out of the way directly one of its fellows wished to come in or out of the nest. The honey accumulated by this species is kept in clusters of cups about the size of a pigeon's egg, at the bottom of the hive and away from the brood-cells. The queen or mother-bee is lighter in colour than the others, and has the hind body twice the length of theirs.

Hockings[36] has given us some details as to the natural history of two of these bees that inhabit Australia, where they are called "Karbi" and "Kootchar," the first being, it is supposed, _Trigona carbonaria_, Smith: it is usually about three-sixteenths of an inch in length, the queen, when fully developed, being nearly twice that length. The comb is built in a most peculiar form, being, it is said, in the shape of a spiral staircase, and tapering towards the ends: honey-pots and pollen are constructed for the storage of food. The comb is encased in wax, and outside it a labyrinth of waxen passages is formed. The entrance to the colony is guarded by a line of bees who inspect every one that arrives, and it is surprising to see how soon a stranger is discovered and pounced upon before it has time even to alight; the intruder, when caught, is held by several bees, who put it on the rack by holding and stretching out its limbs to their full extent, retaining it in this position for as long as an hour, by which time the unfortunate prisoner is usually dead. These bees, as well as many other allied species, fight desperately with their mandibles, and are apparently of a very fierce disposition. The other species, called "Kootchar," is said to produce a very large number of drones, and the habits and dispositions of the bees differ considerably from those of the "Karbi": the entrance to their hive is guarded by a pipe of propolis (a sort of resinous wax) about an inch in length, having an exceedingly sticky outer edge, and it is by this pipe alone that access to the interior can be gained. At night the entrance is closed by numerous minute globules of semi-fluid gum placed against it, thus forming a thin wall full of air-holes. {64}The colonies of "Kootchar" can be united by taking away a queen and then packing her brood-nest, bees and all, against that of the colony it is to be joined to. This cannot be done with the "Karbi." The account given by Mr. Hockings contains a great many other interesting details, and there can be no doubt that a full account of the natural history of these Insects would be very instructive.

Fritz Müller has recorded a singular case bearing on the instinct of these social Insects: he says that a nest of a small _Trigona_ was built in a hollow tree, and that as a consequence of the irregularity of the hole the bees were obliged to give a very irregular shape to their combs of honey. These bees were captured and put in a spacious box (presumably together with the irregular comb, but this he unfortunately does not mention): after a year, "when perhaps not a single bee survived of those which had come from the canella tree," they still continued to build irregular combs, though quite regular combs were built by several other communities of the same species that he had kept. These bees, he also tells us, do not use pure wax for the construction of their combs, but mix it with resin or gum that gives it a peculiar odour and appearance. He captured two communities of a common _Melipona_, one of which had the combs made of dark reddish brown, the other of pale yellowish brown, wax, and in captivity in a distant locality each of the two communities continued to form its comb in the same way, thus showing the continuity that prevails in these cases as long as circumstances permit. Müller thinks this due to imitation, but it seems at least as probable that it is due to perception of the properties of the nest. The nest has a certain colour that the worker-bee matches.

Several species of the _Melipona_ and _Trigona_ were imported from Brazil to France, and kept there for some time in captivity by M. Drory. Girard has published[37] some details as to these colonies, and is of opinion that some of them indicate an intelligence or instinct superior to that of the honey-bee. The queen-bee of _M. scutellaris_ seems to display more intelligence than the corresponding sex of _A. mellifica_. The mode of feeding the larvae apparently differs from that of _A. mellifica_, a provision of pollen being first placed in the cell, then some honey; when {65}sufficient food for the whole consumption of a larva is accumulated the queen deposits an egg in the cell, which is at once completely closed by the worker. The interior of the abode of these bees is quite dark, only a very small orifice being left, and in this a sentinel is constantly on the alert. The same writer states that _Trigona crassipes_ has the very peculiar habit of always locating its brood-comb in the nest of a species of _Termes_.

The honey-bee, _Apis mellifica_ (Fig. 6), is considered the highest form attained by the Anthophilous division of the Hymenoptera. The differentiation of the three forms, male, female, and worker, is here carried to a greater degree of perfection than in the other bees. The drones are the males; the individuals we see gathering honey are always workers, neither the male nor the female in this species taking any part in procuring food for themselves or for the colony. In addition to this the colonies formed may be described as permanent: they do not come to an end at the close of one season, and provision is made for the formation of a new colony while the old one still persists, by means of a peculiar process called swarming. The life-history of _Apis mellifica_ and its anatomy and physiology have been discussed in a whole library of works, and we need only notice the chief features. When a swarm of bees leaves a hive it consists of the queen-bee or female, and a number of workers, these latter being, in fact, the surplus population that has been produced in the hive. The swarm is not a nuptial flight, as is often supposed, but an act of emigration. When this swarm has been housed, the bees commence operations in their new quarters, by secreting wax; they are enabled to do this by having consumed much saccharine food; the wax is produced by means of glands in the hind-body over the inner faces of the ventral plates of the abdominal rings, and it makes its appearance there, after passing from the interior of the body through some peculiar membranes on the ventral segments, in the form of thin projecting plates. These the bee takes off with an apparatus on the hind pair of legs and applies, after working up with the mandibles, to form the cells in which young ones are to be reared and food stored. A large number of bees working in common thus produce the regular and beautiful structure known as the comb; the queen afterwards lays an egg in each cell, and as these soon hatch, great labour is thrown on the workers, which have then to feed the young; this {66}they do by eating honey and pollen, which, being formed into a sort of pap by a portion of their digestive organs, is then regurgitated and given to the young, a quantity of it being placed in the cell, so that the larva is bathed by it, and possibly may absorb the food by the skin as well as the mouth. When the colony is in good progress and young bees emerge, these act as nurses, the older ones cease to prepare food and act as foragers, bringing in honey and pollen which are each stored in separate cells. The larva in the cell increases its size and sheds a very delicate skin several times; when the larva has reached its full size no more food is supplied, but the worker-bees seal up the cell by means of a cover formed of pollen and wax, in such a manner as to be pervious to air: sealed up in the cell the larva spins a cocoon for itself, remains therein for a little time as a larva, then changes to a pupa, and thereafter bites its way out through the cover of the cell, and appears for the first time as a new being in the form of a worker-bee; the whole process of development from the egg-state to the perfect condition of the worker-bee occupies about three weeks.

When the denizens of a hive are about to produce another queen, one or more royal cells are formed; these are much larger than the ordinary worker-cells, and of a quite different form. In this cell is placed an egg, not differing in any respect from the egg that, if placed in an ordinary cell, produces a worker; when the egg has produced a larva this is tended with great care and fed throughout its life with royal jelly. This food appears to be the same as that supplied to an ordinary worker-larva when it is first hatched; but there is this difference, that whereas the worker-larva is weaned, and supplied, after the first period of its existence, with food consisting largely of honey, pollen and water, the queen-larva is supplied with the pap or royal jelly until it is full grown. Some difference of opinion exists as to this royal jelly, some thinking that it is a different substance from what the workers are fed with; and it is by no means improbable that there may be some difference in the secretion of the glands that furnish a part of the material composing the pap. The queen is produced more rapidly than workers are, about sixteen days being occupied in the process of her development. Only one queen is allowed in a hive at a time; so that when several queen-cells are formed, and {67}queen-larvae nurtured in them, the first one that is developed into a perfect queen goes round and stings the royal nymphs to death while they are still in their cells. The production of drones is supposed to depend chiefly on the nature of the egg laid by the queen; it being considered that an unfertilised egg is deposited for this purpose. There is still some doubt on this point, however. Though there is no doubt that drones are produced in great numbers from unfertilised eggs, yet there is not evidence that they cannot also be produced from fertilised eggs.[38] The drone-cells are somewhat larger than the ordinary worker-cells, but this is probably not of much import, and it is said that the larvae intended to produce drones receive a greater proportion of pap than worker-larvae do: about twenty-four days are required to produce a drone from the egg.

From this sketch it will be seen that the production of the worker (or third sex, as it is improperly called, the workers being really females atrophied in some points and specially developed in others) is dependent on the social life, in so far at any rate as the special feeding is concerned. There is good reason for supposing that _A. mellifica_ has been kept in a state of domestication or captivity for an enormous period of time; and this condition has probably led to an increase of its natural peculiarities, or perhaps we should say to a change in them to suit a life of confinement. This is certainly the case in regard to swarming, for this process takes place with comparative irregularity in _Apis mellifica_ in a wild condition. The killing of superfluous queens is also probably a phenomenon of captivity, for it varies even now in accordance with the numbers of the colony. It is interesting to notice that in confinement when a swarm goes from the hive it is the old queen that accompanies it, and this swarm as a rule settles down near the old hive, so that the queen-bee being already fertilised, the new swarm and its subsequent increase are nothing but a division of the old hive, the total products of the two having but a single father and mother. When a second swarm goes off from a hive it is accompanied by a young queen, who frequently, perhaps, in the majority of cases, is unfertilised; this swarm is apt to fly for long distances, so that the probability of cross-fertilisation is {68}greatly increased, as the fertilisation of the young new queen is effected during a solitary flight she makes after the colony has settled down. But in a state of nature the colonies do not send off swarms every year or once a year, but increase to an enormous extent, going for years without swarming, and then when their home is really filled up send off, it may be presumed, a number of swarms in one year. Thus the phenomena of bee-life in a wild condition differ considerably from those we see in artificial confinement. And this difference is probably greatly accentuated by the action of parasites, the proportions of which to their guests are in a state of nature liable to become very great; as we have seen to be the case in _Bombus_.

Under these circumstances it is not a matter for surprise when we find that the honey-bee has formed distinct races analogous to those that exist in the case of the domesticated vertebrate animals. The knowledge of these races is, however, at present very little advanced, and is complicated by the fact that only imperfect information exists as to the true species of the genus _Apis_. There is a bee very like our common honey-bee found in southern Europe called _A. ligustica_; this is certainly a variety of _A. mellifica_, and the same remark applies to a bee found in Egypt, and called _A. fasciata_. This gives the honey-bee a very wide distribution, extending possibly over the whole of the palaearctic region: besides this, the species has been introduced into various other parts of the world.

According to Karsch the honey-bee shows in Germany several varieties, all of which belong to the northern form, which may be spoken of as the _A. domestica_ of Ray; the _A. ligustica_ and _A. fasciata_ form as we have said distinct races, and it is a remarkable fact that these races remain distinct even when imported into other climates; though for how long a period of time this remains true there is very little evidence to show. The northern form, _A. domestica_, is now found in very widely separated parts of the world, in some of which it is wild; Smith mentions it as occurring in the West India islands, throughout the North American continent as far south as Mexico, even in Central and Southern Africa, and in Australia and New Zealand. The var. _ligustica_ has been found also at the Cape of Good Hope. The other species known of the genus _Apis_ all belong to the Old World, so that there is very little doubt that _A. mellifica_ is also {69}a true native of the eastern hemisphere, and its original home may possibly have been not far from the shores of the eastern portion of the Mediterranean sea. Seven or eight other species of _Apis_ are known, all but one of which occur in Asia, extending as far as Timor and Celebes. The exceptional one, _A. adansonii_, occurs in tropical Africa and in Madagascar. Gerstaecker thought these species might be reduced to four, but Smith's statement that the males and even the workers show good distinctive characters seems to be correct. Very little is known as to the honey-bees of China and Japan.

The queen-bee greatly resembles the worker, but has the hind body more elongated; she can, however, always be distinguished from the worker by the absence of the beautiful transverse, comb-like series of hairs on the inner side of the first joint of the hind foot, the planta, as it is called by the bee-keeper: she has also no wax plates and differs in important anatomical peculiarities. The male bee or drone is very different, being of much broader, more robust build, and with very large eyes that quite meet in the middle of the upper part of the head: he also has the hind leg differently shaped. The form of this limb enables the male of _A. mellifica_ to be distinguished from the corresponding sex of allied species of the genus.

[Illustration: Fig. 25.—Portions of hind-feet, 1, of male, 2, of worker, 3, of queen, of the honey-bee; series on the left, outer faces; on the right, inner faces. _a_, Tip of tibia: _b_, first joint; _c_, second joint of tarsus.]

We are indebted to Horne for some particulars as to the habits of _A. dorsata_, an allied East Indian species. He informs us that these bees greatly disfigure buildings, such as the Taj Mahal at Agra, by attaching their pendent combs to the marble arches, and are so pertinacious that it is almost useless to destroy the nests. This bee is said to be so savage in its disposition that it cannot be domesticated; it attacks the sparingly clad Hindoos {70}with great ferocity when they disturb its nest. Notwithstanding its inclination and power to defend its societies this Insect appears to be destroyed wholesale. Colonel Ramsay failed to establish hives of it, because the Insects were eaten up by lizards. The crested honey-buzzard carries off large portions of the comb, and devours it on a branch of some tree near by, quite regardless of the stings of the bees; while the fondness of bears for the honey of the "Dingar," as this species is called, is well known.

Note to P. 33: It has just been discovered that a most remarkable symbiosis, with structural modification of the bee, exists between the females of _Xylocopa_, of the Oriental sub-genus _Koptorthosoma_, and certain Acarids. A special chamber, with a small orifice for entry, exists in the abdomen of the bee, and in this the Acari are lodged.—See Perkins, _Ent. Mag._ xxxv. 1899, p. 37.

Note to P. 80: referring to the habits of social wasps in warm countries. The anticipation we ventured to indulge in is shown to be correct by the recent observations of Von Ihering.[39] He states that social wasps in Brazil may be divided into two great groups by their habits, viz. 1. Summer communities, lasting for one year, and founded annually by fertilised females that have hibernated—example, _Polistes_; 2. Perennial communities, founded by swarms after the fashion of bee colonies—examples, _Polybia_, _Chartergus_.

Note to Vol. V. Pp. 545, 546: The development of _Encyrtus fuscicollis_ has now been studied by Marchal, who has discovered the existence of embryonic dissociation. The chain of embryos and the epithelial tube in which they are placed, are formed as follows: the _Encyrtus_ deposits an egg in the interior of the egg of the _Hyponomeuta_. This does not kill the egg of the Lepidopteron, but becomes included in the resulting caterpillar. The amnion of the Chalcid egg lengthens, and forms the epithelial tube; while the cells within it become dissociated in such a way as to give rise to a chain of embryos, instead of a single embryo.—_C.R. Ac. Paris_, cxxvi. 1898, p. 662, and translation in _Ann. Nat. Hist._ (7), ii. 1898, p. 28.

{71}