CHAPTER III

HYMENOPTERA ACULEATA _CONTINUED_—DIVISION III. FOSSORES OR FOSSORIAL SOLITARY WASPS—FAMILY SCOLIIDAE OR SUBTERRANEAN FOSSORS—FAMILY POMPILIDAE OR RUNNERS—FAMILY SPHEGIDAE OR PERFECT-STINGERS

DIVISION III. FOSSORES.

_Aculeate Hymenoptera, in which the abdomen, though very diverse in form, does not bear prominences on the upper aspect of the basal segments; front wing without longitudinal fold along the middle; hairs of body not plumose. Only two forms (male and female) of each species._

Fossorial Hymenoptera are distinguished from other Aculeates at present only by negative characters, _i.e._ they are Aculeates, but are not ants, bees or wasps. According to their habits they fall into four, by no means sharply distinguished, groups—(1) those that form no special receptacles for their young, but are either of parasitic or sub-parasitic habits, or take advantage of the abodes of other Insects, holes, etc.; (2) constructors of cells of clay formed into pottery by the saliva of the Insect, and by drying; (3) excavators of burrows in the ground; (4) makers of tunnels in wood or stems of plants. Several species make use of both of the last two methods. The habits are carnivorous; the structures formed are not for the benefit of the makers, but are constructed and stored with food for the next generation. Their remarkable habits attracted some attention even 2000 years or more ago, and were to some extent observed by Aristotle. The great variety in the habits of the species, the extreme industry, skill, and self-denial they display in carrying out their voluntary labours, render them one of the most instructive groups of the animal kingdom. There are no social or gregarious {91}forms, they are true individualists, and their lives and instincts offer many subjects for reflection. Unlike the social Insects they can learn nothing whatever from either example or precept. The skill of each individual is prompted by no imitation. The life is short, the later stages of the individual life are totally different from the earlier: the individuals of one generation only in rare cases see even the commencement of the life of the next; the progeny, for the benefit of which they labour with unsurpassable skill and industry, being unknown to them. Were such a solicitude displayed by ourselves we should connect it with a high sense of duty, and poets and moralists would vie in its laudation. But having dubbed ourselves the higher animals, we ascribe the eagerness of the solitary wasp to impulse or instinct, and we exterminate their numerous species from the face of the earth for ever, without even seeking to make a prior acquaintance with them. Meanwhile our economists and moralists devote their volumes to admiration of the progress of the civilisation that effects this destruction and tolerates this negligence.

[Illustration: Fig. 37.—_Sceliphron nigripes_ ♀ (Sub-Fam. Sphegides). Amazons. × 3/2.]

{92}It should be noted that in the solitary as in the social Insects the males take no part whatever in these industrial occupations, and apparently are even unaware of them. It is remarkable that, notwithstanding this, the sexual differences are in the majority less than is usual in Insects. It is true that the various forms of Scoliidae exhibit sexual distinctions which, in the case of Thynnides and Mutillides are carried to an extreme degree, but these are precisely the forms in which skill and ingenuity are comparatively absent, the habits being rather of the parasitic than of the industrial kind, while the structure is what is usually called degraded (_i.e._ wingless). The great difference between the habits of the sexes, coupled with the fact that there is little or no difference in their appearance, has given rise to a curious Chinese tradition with regard to these Insects, dating back to Confucius at least.[45] The habit of stinging and storing caterpillars in a cell, from which a fly similar to itself afterwards proceeds having been noticed, it was supposed to be the male that performed these operations; and that when burying the caterpillars he addressed to them a spell, the burden of which is "mimic me." In obedience the caterpillars produce the wasp, which is called to this day "Jiga," that is in English "mimic me." The idea was probably to the effect that the male, not being able to produce eggs, used charmed caterpillars to continue the species.

SUMMARY OF THE PREY OF FOSSORES.

Group of Fossores. Food or Occurrence.

Fam. Scoliidae. Sub-Fam. Mutillides As parasites on Hymenoptera Aculeata. " Thynnides (?) Parasites on Lepidopterous pupae. " Scoliides Larvae of Coleoptera [(?) spiders in the case of _Elis 4-notata_]. " Rhopalosomides Unknown. " Sapygides The provisions stored by bees. Caterpillars (teste Smith). Fam. Pompilidae Spiders. Rarely Orthoptera (Gryllidae and Blattidae, teste Bingham) or Coleoptera. Fam. Sphegidae. Sub-Fam. Sphegides Orthoptera (especially Locustidae), larvae of Lepidoptera, Spiders [(?) same species (_Sceliphron madraspatanum_ and _Sphex coeruleus_), both spiders and caterpillars]. " Ampulicides Orthoptera (Blattidae only). {93} " Larrides Orthoptera of various divisions. Aculeate Hymenoptera, in the case of _Palarus_. [Spiders stolen from nests of _Pelopaeus_ by _Larrada_.] " Trypoxylonides Spiders, caterpillars, Aphidae. " Astatides _Astata boops_ uses Pentatomid bugs, cockroaches, and even Aculeate Hymenoptera (_Oxybelus_, teste Smith). " Bembecides Diptera and _Cicada_. " Nyssonides Diptera, Homoptera (_Gorytes mystaceus_ takes _Aphrophora_ out of its "cuckoo- spit"). " Philanthides Aculeate Hymenoptera (_Philanthus_). Hard beetles, viz. Curculionidae, Buprestidae, Chrysomelidae (_Cerceris_). " Mimesides Small Homoptera, even Aphidae. Diptera (Tipulidae) in Hawaii. " Crabronides Diptera, Aphidae [? the same species of wasps both of these]. Other small Homoptera. Ants (in the case of _Fertonius_). Parasitic Hymenoptera (in the case of _Lindenius_).

Great diversity of opinion exists as to the classification of the Fossores. This arises chiefly from the incomplete state of the collections studied, and from the fact that the larger part of the works published are limited to local faunae. Opinions as to the families vary; some admitting only three or four, others upwards of twenty. After consideration of the various views, the writer thinks it best to admit at present only three families, which speaking broadly, correspond with habits, viz. (1) Scoliidae, subterranean stingers; (2) Pompilidae, runners; (3) Sphegidae, stingers above ground.

1. Scoliidae. Pronotum and tegulae in contact. Abdomen with the plane of the ventral surface interrupted by a chink between the first and second segments. Numerous wingless forms.

2. Pompilidae. Pronotum and tegulae in contact. Abdomen with the plane of the ventral surface not interrupted by a chink. Legs very long. No wingless forms.

3. Sphegidae. Pronotum and tegulae not in contact. No wingless forms.

We shall treat as sub-families those divisions of Scoliidae and Sphegidae considered by many as families.

{94}FAM. 1. SCOLIIDAE.

The members of this family, so far as is known, display less perfect instincts than the Sphegidae and Pompilidae, and do not construct cells or form burrows. Information as to the habits is almost confined to European forms. We adopt five sub-families.

SUB-FAM. 1. MUTILLIDES.—_The sides of the pronotum reach the tegulae: the female is destitute of wings and ocelli, frequently having the parts of the thorax so closely soldered that the divisions between them are obliterated: the males are winged, furnished with ocelli, and having the thoracic divisions distinct; intermediate tibiae with two apical spurs. Front wing with two or three sub-marginal cells. The larvae live parasitically at the expense of other Hymenoptera Aculeata._

The Mutillides have some resemblance to ants, though, as they are usually covered with hair, and there is never any node at the base of the abdomen, they are readily distinguished from the Formicidae. The great difference between the sexes is their most striking character. Their system of coloration is often very remarkable, the velvet-like pubescence clothing their bodies being variegated with patches of sharply contrasted vivid colour; in other cases the contrast of colour is due to bare, ivory-like spaces. They have the faculty of stridulating, the position and nature of the organ for the purpose being the same as in ants.

Very little exact information exists as to the habits and life-histories of the species. Christ and Drewsen, forty or fifty years ago, recorded that _M. europaea_ lives in the nests of bees of the genus _Bombus_, and Hoffer has since made some observations on the natural history of the same species in South East Europe, where this _Mutilla_ is found in the nests of ten or eleven species of _Bombus_, being most abundant in those of _B. agrorum_ and _B. variabilis_; occasionally more individuals of _Mutilla_ than of bees may be found in a nest. He supposes that the egg of the _Mutilla_ is placed in the young larva of the _Bombus_, and hatches in about three days; the larva feeds inside the bee-larva, and when growth is completed a cocoon is spun in the interior of the pupa-case of the bee. When the perfect Insects emerge, the males leave the nest very speedily, but the females remain for some time feeding on the bees' honey. Females are usually produced in greater numbers than males. This account leaves {95}much to be desired. From the observations of Radoszkowsky it is clear that other species of Mutillides are by no means confined to the nests of _Bombus_ but live at the expense of Aculeate Hymenoptera of various groups. This naturalist asserts that the basal abdominal segment of the parasite resembles in form that of the species on which it preys.

The apterous condition of the females of Mutillides and Thynnides is very anomalous in the Fossors; this sex being in the other families distinguished for activity and intelligence. The difference between the sexes is also highly remarkable. The males differ from the females by the possession of wings and by the structural characters we have mentioned, and also in a most striking manner in both colour and form; Burmeister, indeed, says that in South America—the metropolis of Mutillides—there is not a single species in which the males and females are alike in appearance; this difference becomes in some cases so extreme that the two sexes of one species have been described as Insects of different families.

[Illustration: Fig. 38—_Mutilla stridula._ Europe. A, Male; B, female.]

Upwards of one thousand species are assigned to the genus _Mutilla_, which is distributed over the larger part of the world; there is so much difference in these species as to the nervuration of the wings in the males, that several genera would be formed for them were it not that no corresponding distinctions can be detected in the females. Three or four species of _Mutilla_ are described as being apterous in the male as well as in the female sex; they are very rare, and little is known about them. Only three species of Mutillides occur in Britain, and they are but rarely seen, except by those who are acquainted with their {96}habits. The African and East Indian genus, _Apterogyna_, includes some extremely peculiar Hymenoptera; the males have the wing nervuration very much reduced, and the females are very ant-like owing to the deep constriction behind the first abdominal ring.

SUB-FAM. 2. THYNNIDES.—_Males and females very different in form; the male winged, the front wing with three, or only two, sub-marginal cells; the female wingless and with the thorax divided into three sub-equal parts._

[Illustration: Fig. 39—_Methoca ichneumonides._ A, Male; B, female. Britain.]

The Thynnides are by some entomologists not separated from the Mutillides; but the distinction in the structure of the thorax of the females is very striking. In the Thynnides the nervuration of the wing appears always to extend to the outer margin, and in the Mutillides not to do so. This family is represented in Britain by a single very rare Insect, _Methoca ichneumonides_: to the unskilled observer the female would appear to be without doubt an ant. This Insect is by some considered as the type of a family distinct from the Thynnides proper. Thynnides are numerous in Australia. Very little is really known as to their habits, though it has been stated that they are parasitic on Lepidoptera, Bakewell having obtained specimens from subterranean cocoons of that Order. Those who are interested in differences between the sexes of one species should examine the extraordinary examples of that phenomenon presented by the Thynnides; the dissimilarity throughout the group—which is now of considerable extent—being so extreme that no entomologist would from simple inspection believe the two sexes to have any connection; but the fact that they are so connected has been demonstrated beyond doubt. In very few {97}cases, however, have the sexes been matched, so that at present males are no doubt standing in the lists of Hymenoptera as one species and their females as other species.

SUB-FAM. 3. SCOLIIDES.—_Pronotum reaching back to the tegulae; legs stout; intermediate tibiae with one apical spur; both sexes winged; the nervures not extending to the posterior_ (i.e. _distal_) _margin_.

This group includes some of the largest and most powerful of the Aculeate Hymenoptera. Its members are usually hairy Insects with thick legs, the colour being black, more or less variegated with bands or spots of red or yellow; the hind body is elongate, has only a very short pedicel, and in the male is usually terminated by three projecting spines. The pronotum is of variable dimensions, but its front angles are always co-adapted with the points of insertion of the front wings. The nervuration of the front wings is confined to the basal part, the extensive apical or outer area possessing no nervures. There is frequently a great difference in the size of the two sexes of the same species, the female being very much larger than the other sex. The larvae, so far as is known, devour those of Lamellicorn Coleoptera.

[Illustration: Fig. 40.—_Scolia haemorrhoidalis_ ♀. Europe.]

Fabre has investigated the habits of some of the species of Scoliides found in France, and has informed us that their means of subsistence consists of larvae of the larger Lamellicorn beetles, _Cetonia_, _Oryctes_, _Anoxia_, and _Euchlora_; these beetles belong to very different divisions of the Lamellicornia, but they have in common the fact that their larvae are of subterranean habits, living in the earth or in accumulations of débris in which there is a large proportion of vegetable matter or roots. The female _Scolia_ penetrates into the ground in order to find the Lamellicorn larvae necessary as food for its progeny. _Scolia bifasciata_ {98}attacks the larvae of several species of _Cetonia_, and _S._ (_Colpa_) _interrupta_ chooses the larvae of the chafers _Anoxia villosa_ and _A. matutinalis_. The mother _Scolia_ enters the ground in August or September, and having found a suitable larva stings it and deposits an egg on the ventral surface of the prey; the paralysed larva is left where it was found, no attempt being made to place it in a special receptacle. The egg is placed on the ventral surface, well behind the feet, under a mass of matter in the alimentary canal. Shortly after being hatched the young destroyer penetrates with its head the skin of the victim, and in this position commences to feed; it is necessary that it should obtain its food without killing the _Cetonia_ larva, for it cannot prosper on decaying food, so that if the _Cetonia_ larva die the _Scolia_ larva likewise perishes; the latter, accordingly, does not withdraw its head from the interior of the victim, but remains always in the same position, as it grows larger extending its head forwards into the front part of the interior of its victim; the internal organs of the latter are consumed in a systematic order so as to delay bringing about its death till the last moment, and thus all the interior of the _Cetonia_ larva is appropriated till nothing remains but an empty skin. By a series of experiments, Fabre showed how essential it is that this apparently revolting operation should be carried on with all details strictly _en règle_. If the head of the _Scolia_ larva be taken out from the victim and applied to another part of the body of the _Cetonia_, the result is that it cannot eat; even if it be replaced in the original situation, after being taken away, it frequently happens that the _Cetonia_ larva dies, its death involving also that of the destroyer. It is necessary, too, that the victim should be paralysed, for if an intact _Cetonia_ larva be taken and bound down in such a position that it cannot move, and if a small orifice in its skin be made in the proper spot and a young _Scolia_ larva be placed on it, the little parasite will avail itself of the opportunity and commence to feed on the larva provided for it, but the latter will speedily die, and the _Scolia_ necessarily perishes with it. Thus both the paralysis of the victim and the special mode of eating are essential to the life of the _Scolia_. The operation of stinging the larva so as to produce the necessary paralysis, or rather insensibility, is a difficult one, and requires great skill and patience. The _Cetonia_ larva is of large size, and must be pierced in one particular spot; {99}in order to reach this the _Scolia_ mounts on its victim, and is frequently dislodged by its struggles; sooner or later, however, the proper position is obtained by the wasp, and the larva is then stung in the exact spot necessary to allow the sting (and the poison introduced by it) to reach the most important of the nervous ganglia that control the movements of the body, this spot being, in the case of the _Cetonia_, the line of demarcation between the pro- and meso-thorax, on the middle line of the ventral surface of the body. The _Scolia_ gives but one sting to the victim, and this it will not administer until it can do so exactly in the proper place. This practice of devouring the victim slowly, without killing it till all is eaten, is very widely spread in the Hymenoptera, and it is satisfactory to find that we may infer from Fabre's observations that it is not so horrible as it would at first appear; for it is probable that the stinging prevents decomposition of the victim, not by reason, as some have supposed, of the poison injected by the wasp having an antiseptic effect, but rather by means of destroying sensibility, so that the creature does not die from the pain, as it is believed it did in certain cases where Fabre induced the young _Scolia_ larva to feed on a victim that had not been stung. We may here remark that very little exact information exists as to the operation of stinging. Fabre attaches great importance to the sting being inflicted on a nerve-ganglion. Whether a sting that did not reach this part might not have a sufficient effect appears, however, doubtful.[46]

A remarkable form of Scoliides, with wings of smaller size than usual and deeply divided, has been described by Saunders under the name _Pseudomeria graeca_. Still more remarkable is _Komarovia victoriosa_ found in Central Asia; in this Insect the male retains the appearance of a slender, pallid _Scolia_, but the female differs totally in form, and has the peculiar wings so reduced in size as to be useless for flight.

SUB-FAM. 4. SAPYGIDES.—_Closely allied to the Scoliides, but possessing slender legs and antennae; also the first abdominal segment is less disconnected from the second, so that the outline {100}is less interrupted; the eyes are deeply emarginate; the hind body is not spinose at the apex._

[Illustration: Fig. 41.—_Sapyga 5-punctata_ ♀, Britain.]

The economy of _Sapyga_, the only genus, has been the subject of difference of opinion. The views of Latreille and others that these species are parasitic upon bees is confirmed by the observations of Fabre, from which it appears that _S. 5-punctata_ lives in the burrows of species of the bee-genus _Osmia_, consuming the store of provisions, consisting of honey-paste, that the bee has laid up for its young. According to the same distinguished observer, the _Sapyga_ larva exhibits hypermetamorphosis (_i.e._ two consecutive forms), and in its young state destroys the egg of the bee; but his observations on this point are incomplete and need repetition. We have two species of _Sapyga_ in Britain; they differ in colour, and the sexes of _S. 5-punctata_ also differ in this respect; the abdomen, spotted with white in both sexes is in the female variegate with red. Smith found our British _Sapyga 5-punctata_ carrying caterpillars.

SUB-FAM. 5. RHOPALOSOMIDES.—_Antennae elongate, spinigerous; ocelli very prominent; tarsi of peculiar structure, their claws bifid._

[Illustration: Fig. 42—_Rhopalosoma poeyi._ A, female imago; B, front of head. Cuba. (After Westwood.)]

This sub-family has recently been proposed by Ashmead[47] for {101}an extremely rare American Insect that had previously been placed by Cresson among parasitic Hymenoptera. Westwood classed _Rhopalosoma_ among Diploptera, saying of it "animal quoad affinitates excrucians." We reproduce Westwood's figure, but not being acquainted with the Insect we can express no opinion as to whether it is allied to the Scoliidae or to the Sphegidae. The habits are, we believe, quite unknown.

FAM. 2. POMPILIDAE.

_Pronotum at the sides reaching the tegulae; hind body never definitely pedicellate, though the first segment is sometimes elongate and conical; hind legs long; eyes elliptic in form, not emarginate._

The Pompilidae are perhaps the most extensive and important of the groups of Fossores, and are distributed over all the lands of the globe, with the exception of some islands and of the inclement arctic regions. The sting of the Pompilidae, unlike that of most of the Fossores, inflicts a burning and painful wound; the creatures sometimes attain a length of two or three inches, and a sting from one of these giants may have serious results. Although there is considerable variety in the external form of the members of the group, the characters given above will enable a Pompilid to be recognised with approximate certainty. The elongation of the hind legs includes all the parts, so that while the femur extends nearly as far back as the extremity of the body—in dried examples at any rate—the tibiae and the long tarsi extend far beyond it; thus these Insects have great powers of running; they are indeed remarkable for extreme activity and vivacity. They may frequently be seen running rapidly on the surface of the ground, with quivering wings and vibrating antennae, and are probably then employed in the search for prey, or some other of the operations connected with providing a store of food for their young. Spiders appear to be their special, if not their only, prey. Several authors have recorded details as to the various ways in which the prey is attacked. Fabre has observed the habits of several species, and we select his account of the _modus operandi_ of species of the genera _Pompilus_ and _Calicurgus_, in their attacks on poisonous spiders that inhabit holes in the ground or in walls. The wasp goes to the mouth of the spider's burrow, and the latter then dashes to the entry, apparently enraged at the audacity of its persecutor.

{102}[Illustration: Fig. 43.—_Calicurgus hyalinatus_ ♀. Britain.]

The _Calicurgus_ will not actually enter a burrow when there is a spider in it, because if it did so the spider would speedily dispose of the aggressor by the aid of its poisonous fangs. The _Calicurgus_, therefore, has recourse to strategy with the object of getting the spider out of its nest; the wasp seizes its redoubtable foe by one foot and pulls; probably it fails to extract the spider, and in that case rapidly passes to another burrow to repeat its tactics; sooner or later a spider is in some moment of inattention or incapacity dragged from its stronghold, and, being then comparatively helpless, feels itself at a disadvantage and offers but a feeble resistance to the wasp, which now pounces on its body and immediately inflicts a sting between the fangs of the foe, and thus at once paralyses these dangerous weapons; thereafter it stings the body of the spider near to the junction of the abdomen and cephalothorax, and so produces complete inactivity. Having secured its prey, the wasp then seeks a suitable hole in which to deposit it; probably an empty burrow of a spider is selected for the purpose, and it may be at a height of several feet in a wall; the Hymenopteron, walking backwards, drags its heavy prey up the wall to bring it to the den. When this is accomplished an egg is deposited on the spider, and the wasp goes in search of a fragment or two of mortar, with which the mouth of the burrow is finally blocked. Fabre's accounts refer to the habits of several species, and give a good insight into some points of the instincts of both the spider and the wasp. It seems that a sense of superiority is produced in one or other of the foes, according as it feels itself in suitable conditions; so that though a spider out of its burrow and on the ground is speedily vanquished by the Pompilid, yet if the two be confined together in a vase, both are {103}shy and inclined to adopt defensive or even evasive tactics, the result probably being that the wasp will be killed by the spider during the night, that being the period in which the attacking powers of the spider are more usually brought into play.

It seems to be the habit of some _Pompilus_ to procure a victim before they have secured a place for its reception; and Fabre took advantage of this fact, and made very interesting observations on some points of the instinct of these wasps. Having found a _Pompilus_ that, after having caught a spider and paralysed it, was engaged in making a retreat for its reception, he abstracted the booty, which was deposited at the top of a small tuft of vegetation near to where the _Pompilus_ was at work. In this case the burrow in course of preparation was subterranean, and was formed by the _Pompilus_ itself, which therefore could not, while it was engaged underground, see what took place near it. It is the habit of the wasp to leave its work of excavation from time to time, and to visit the prey as if to assure itself of the safety of this object, and to enjoy the satisfaction of touching it with the mouth and palping it. Desirous of testing the wasp's memory of locality, Fabre took the opportunity, while the Insect was working at the formation of its burrow, of removing, as we have said, the booty from the place where it had been deposited, and putting it in another spot some half-yard off. In a short time the _Pompilus_ suspended work and went straight to the spot where it had deposited its property, and finding this absent, entered on a series of marches, counter-marches, and circles round the spot where it had left the prey, as if quite sure that this was really the place where the desired object ought to be. At last convinced that the paralysed prey was no longer where it had been placed, the _Pompilus_ made investigations at a greater distance and soon discovered the spider. Fabre recounts that its movements then appeared to indicate astonishment at the change of position that it thus ascertained to have occurred. The wasp, however, soon satisfied itself that this was really the very object it was seeking, and seizing the spider by the leg slightly altered its position by placing it on the summit of a small tuft of vegetation; this latter proceeding being apparently always carried out by this species of _Pompilus_. Then it returned to its excavation, and Fabre again removed the spider to a third spot; the wasp when it next rested from its work made its way {104}immediately to the second spot, where it had last left the spider, thus showing that it possessed an accurate memory for locality; the wasp was very much surprised at the absence of the valued prize and persisted in seeking it in the immediate vicinity without once returning to the place where it had been first located. Fabre repeated this manoeuvre five times, and the _Pompilus_ invariably returned at once to the spot where it had last left its prey. The acute memory for localities displayed by this Insect seems to be more or less general throughout the Aculeate Hymenoptera, and is of very great importance to them. The power of finding the object appears to depend on sight, for when Fabre, after removing the spider to a fresh spot, made a slight depression in the ground, placed the spider in it and covered it over with a leaf, the wasp did not find it. At the same time, the Insect's sight must be a very different sense from our own, for the wasp, when seeking its lost booty, frequently passed within a couple of inches of it without perceiving it, though it was not concealed.

Belt gives an example of the habits of the Mexican _Pompilus polistoides_. He noticed it, when hunting for spiders, make a dart at a web in the centre of which a spider was stationed; by this movement the creature was frightened and fell to the ground, where it was seized by the wasp and stung. The _Pompilus_ then dragged its prisoner up a tree and afterwards flew off with it, the burden being probably too heavy for conveyance to the nest without the vantage of an elevation to start from.

Several modifications adopted by Pompilidae in their mode of stinging their spider-victims have been recorded by Ferton; these we cannot allude to in detail, but will nevertheless mention that one species stings the body of its spider-prey at random, and that in other cases it would appear that the paralysis of the spider is evanescent. In short, there are various degrees of perfection in the details of the art of stinging.

The most remarkable of the forms of Pompilidae are the numerous species of _Pepsis_, a genus peculiar to America, whence upwards of 200 species are already known.[48] Some of them attain a length of two inches or more, and are able to conquer the largest spiders; even the formidable _Mygale avicularis_ succumbs to their agility and skill. Some of these _Pepsis_ have beautifully coloured wings; according to Cameron, this may be {105}due to scales. _P. formosus_, Say, is called in Texas the tarantula-killer; according to Buckley, its mode of attack on the huge spider is different from that made use of by its European ally. When it discovers a tarantula it flies "in circles in the air, around its victim. The spider, as if knowing its fate, stands up and makes a show of fighting, but the resistance is very feeble and of no avail. The spider's foe soon discovers a favourable moment and darts upon the tarantula, whom it wounds with its sting, and again commences flying in circles." The natural retreat of this huge spider, _Mygale hentzii_, is in holes in the ground, and this account does not inform us whether the spider allows itself to be overcome when in its nest, or is only attacked when out of its retreat.

The genus _Mygnimia_ includes a very large number of species, and has a wider geographical distribution than _Pepsis_, being found in the tropical regions of both the Old and New Worlds, some of them rivalling in size and ferocity the larger specimens of the genus _Pepsis_. In the Insects of this genus there is usually a more or less distinct small space of more pallid colour on the middle of each front wing. _Parapompilus_ is a curious genus consisting of Insects of a great variety of peculiar coloration, and having the wings short, so as to be of little use for flight. _P. gravesii_ is an inhabitant of Chili.

_Agenia carbonaria_ and _A. hyalipennis_ are small and feeble Insects inhabiting the south of Europe. _A. carbonaria_ extends to the south of England. They construct, as nests for their offspring, small earthenware vessels, differing in form according to the species, those of _A. hyalipennis_ being vase-like in shape, while those of _A. carbonaria_ are contracted near the mouth, something after the fashion of a wide-mouthed bottle. The Insect is able by some means—Fabre thinks by the use of saliva—to varnish the interior of the vessel so that it will not absorb water; the outside of the cells is, however, not so protected, and speedily crumbles away when exposed to the action of water; hence the vessel is placed in a protected situation, such as in a tree-stump, or a hole in a wall, or even in an empty snail-shell under a heap of stones. The cells are stored with spiders that have been paralysed by stinging and that serve as food for the larva of the _Agenia_. The larva of _A. carbonaria_ has been described, and some particulars as to its habits have been given by Verhoeff. {106}It has been stated that this wasp does not paralyse its prey by stinging, but substitutes a process of biting to prevent the spider from hurting the larva that is to feed on it; and Verhoeff's observations seem to show that the legs of the spider are broken by some proceeding of the kind. The _Agenia_ larva is of peculiar shape, the head not being inflexed, while the pleurae of each segment, from the second onwards, are prominent, so as to give the outline of the body a scalloped appearance. This larva is much infested by an Ichneumon that devours, it appears, not only the larva itself, but also the spider that was destined to be food for the larva. Verhoeff seems to have found some evidence that _Pompilus sericeus_ may also be a parasite on the _Agenia_.

The construction of earthenware cells, instead of the burrows usual in Pompilidae, by the species of this genus is one of the cases alluded to in our introductory remarks as to allied Fossores exhibiting different habits. Mr. Pride has recently sent us from Brazil similar earthen vessels constructed by some Pompilid.

The habits of Pompilids of the genus _Ceropales_ are analogous to those of the parasitic bees. Pérez has recently given us information as to a very curious form of parasitism in this genus; he says that when a _Pompilus_ has obtained a spider as provision for its young, it is pursued by a _Ceropales_, which lays an egg on the spider, thus as it were substituting in advance its own young for that of the _Pompilus_. Information as to the subsequent course of events in this case is not at present forthcoming. In another case a _Ceropales_ was observed to oviposit on the spider, not while this is being carried in, but subsequently by entering the nest for the purpose; a habit quite similar to that of some parasitic bees. Ferton has recently made the unexpected discovery that some _Pompilus_ act as robbers; one individual taking away by force the spider that another has captured and is carrying off.

Lichtenstein described a Pompilid larva, that he afterwards ascertained to be _Calicurgus hyalinatus_, as possessing the extraordinary habit of feeding as an external parasite fixed to the dorsal surface of a spider; thus repeating, it would appear, the habits of some of the Ichnemonidae, though the perfect Insect (Fig. 143) does not differ in structure from its congeners. Emery has given an account of some Pompilids that do not bury their prey, but after stinging it and depositing an egg, simply leave the spider on the spot.

{107}Buller has described the habits of a Pompilid in New Zealand; his account is interesting because it shows a remarkable similarity in the proceedings of this antipodean wasp to those of its congeners on our own side of the world. The species is not scientifically named, but it appears that it is known in New Zealand as "the Mason-bee." It forms a nest of yellow clay consisting apparently of about eight cells, each of which is filled with one or more spiders in a paralysed condition. The figure given of the larva of this Insect by Buller shows it to possess a peculiarly formed head.

It is pleasing to find that Pompilidae do not make use of cruel methods when others will serve their purpose. We are informed that a large Australian Pompilid—_Priocnemis bicolor_—may find a _Cicada_ sucking sap from a hole it has pierced in a tree. The _Priocnemis_ has not the art of making the puncture necessary to procure sap, so the wasp seizes the _Cicada_, and shakes it till it leaves its hold and flies away, when the _Priocnemis_ takes its place and sips the sap. It is added that the wasp never hurts the Cicada.

FAM. 3. SPHEGIDAE.

_Pronotum free from the tegulae; when the stigmatic lobes extend as far back as the wing-insertion, they are placed below it and separated by a space from it._

This large assemblage of Fossores is the one about which the greatest difference of opinion prevails. It is based entirely on the prothoracic characters mentioned above, and cannot be looked on as natural. We shall, however, follow Kohl[49] in treating for the present as only one family the divisions considered by many as distinct families. They are ten in number.

SUB-FAM. 1. SPHEGIDES.—_Hind body with a slender pedicel of variable length; two spurs on the middle tibia. The propodeum usually horizontally elongate_.[50]

This group includes a great number of species, about 200 of which are referred to the genus _Sphex_.

{108}The habits of one species of this genus have been fully described by Fabre; he assigns to the species the name of _S. flavipennis_, but Kohl considers that it is more probably _S. maxillosus_. This Insect forms its nests, in the South of France, in the ground, excavating a main shaft with which are connected cells intended for the reception of the provisions for the young. The entrance to the burrow is formed by piercing a hole in the side of a very slight elevation of the soil. Thus the entrance to the construction consists of a horizontal gallery, playing the part of a vestibule, and this is used by the _Sphex_ as a place of retreat and shelter for itself; at the end of the vestibule, which may be two or three inches long, the excavation takes an abrupt turn downwards, extending in this manner another two or three inches, and terminating in an oval cell the larger diameter of which is situate in a horizontal plane. When this first cell has been completed, stored with food, and an egg laid in it, the entrance to it is blocked up, and another similar cell is formed on one side; a third and sometimes a fourth are afterwards made and provisioned, then the Insect commences anew, and a fresh tunnel is formed; ten such constructions being the number usually prepared by each wasp. The Insect works with extreme energy, and as the period of its constructive activity endures only about a month, it can give but two or three days to the construction and provisioning of each of its ten subterranean works. The provisions, according to Fabre, consist of a large species of field-cricket, of which three or four individuals are placed in each cell. Kohl states, however, that in Eastern Europe an Insect that he considers to be the same species as Fabre's _Sphex_, makes use of locusts as provisions, and he thinks that the habit may vary according to the locality or to the species of Orthoptera that may be available in the neighbourhood. However that may be, it is clear from Fabre's account that this part of the _Sphex's_ duties do not give rise to much difficulty. The cricket, having been caught, is paralysed so that it may not by its movements destroy the young larva for whose benefit it is destined. The _Sphex_ then carries it to the burrow to store it in one of the cells; before entering the cell the Insect is in the habit of depositing its prey on the ground, then of turning round, entering the burrow backwards, seizing as it does so the cricket by the antennae, and so dragging it into the cell, itself going {109}backwards. The habit of depositing its prey on the ground enabled Fabre to observe the process of stinging; this he did by himself capturing a cricket, and when the wasp had momentarily quitted its prey, substituting the sound cricket for the paralysed one. The _Sphex_, on finding this new and lively victim, proceeds at once to sting it, and pounces on the cricket, which, after a brief struggle, is overcome by the wasp; this holds it supine, and then administers three stings, one in the neck, one in the joint between the pro- and meso-thorax, and a third at the base of the abdomen, these three spots corresponding with the situation of the three chief nervous centres governing the movements of the body. The cricket is thus completely paralysed, without, however, being killed. Fabre proved that an Insect so treated would survive for several weeks, though deprived of all power of movement. Three or four crickets are placed by the wasp in each cell, 100 individuals or upwards being thus destroyed by a single wasp. Although the sting has such an immediate and powerful effect on the cricket, it occasions but a slight and evanescent pain to a human being; the sting is not barbed, as it is in many bees and true wasps, and appears to be rarely used by the Insect for any other purpose than that of paralysing its victims. The egg is laid by the _Sphex_ on the ventral surface of the victim between the second and third pairs of legs. In three or four days the young larva makes its appearance in the form of a feeble little worm, as transparent as crystal; this larva does not change its place, but there, where it was hatched, pierces the skin of the cricket with its tiny head, and thus begins the process of feeding; it does not leave the spot where it first commenced to feed, but gradually enters by the orifice it has made, into the interior of the cricket. This is completely emptied in the course of six or seven days, nothing but its integument remaining; the wasp-larva has by this time attained a length of about 12 millimetres, and makes its exit through the orifice it entered by, changing its skin as it does so. Another cricket is then attacked and rapidly consumed, the whole stock being devoured in ten or twelve days from the commencement of the feeding operations; the consumption of the later-eaten crickets is not performed in so delicate a manner as is the eating of the first victim. When full-grown, the process of forming a cocoon commences: this is a very elaborate operation, for the encasement consists of three layers, in {110}addition to the rough silk that serves as a sort of scaffolding on the exterior: the internal coat is polished and is of a dark colour, owing to its being coloured with a matter from the alimentary canal: the other layers of the cocoon are white or pale yellow. Fabre considers that the outer layers of the cocoon are formed by matter from the silk-glands, while the interior dark coat is furnished by the alimentary canal and applied by the mouth of the larva: the object of this varnish is believed to be the exclusion of moisture from the interior of the cocoon, the subterranean tunnels being insufficient for keeping their contents dry throughout the long months of winter. During the whole of the process of devouring the four crickets, nothing is ejected from the alimentary canal of the larva, but after the cocoon is formed the larva ejects in it, once for all, the surplus contents of the intestine. Nine months are passed by the Insect in the cocoon, the pupal state being assumed only towards the close of this period. The pupa is at first quite colourless, but gradually assumes the black and red colour characteristic of the perfect wasp. Fabre exposed some specimens of the pupa to the light in glass tubes, and found that they went through the pupal metamorphosis in just the same manner as the pupae that remained in the darkness natural to them during this stage of their existence.

_Sphex coeruleus_ is frequently stated to have the habit of provisioning its nests with both Orthoptera and Spiders; but Kohl considers with reason that this record is, as regards spiders, a mistake, arising probably from a confusion with some other Insect of similar appearance, such as _Pelopaeus_ (_Sceliphron_) _coeruleus_. _S. coeruleus_ is no doubt the same as _S._ (_Chlorion_) _lobatus_, which Rothney observed in East India, provisioning its nests with Orthoptera. He discovered a nest in process of construction, and during the absence of the mother-wasp abstracted from the burrow a large field-cricket that she had placed in it; he then deposited the Orthopteron near the cell; the parent _Sphex_ on returning to work entered the tunnel and found the provision placed therein had disappeared; she came out in a state of excitement, looked for the missing cricket, soon discovered it, submitted it to the process of malaxation or kneading, and again placed it in the nest, after having cleared it from some ants that had commenced to infest it. She then disappeared, and Rothney repeated the experiment; in due course the same series {111}of operations was performed, and were repeated many times, the _Sphex_ evidently acting in each case as if either the cricket had disappeared owing to its being incompletely stunned, or to its having been stolen by ants. Finally, the observer placed the cricket at a greater distance from the nest, when it recovered from the ill-treatment it had received sufficiently to make its escape. The points of interest in this account are the fact that the cricket was only temporarily paralysed, and that the wasp was quite able to cope with the two special difficulties that must frequently occur to the species in its usual round of occupations.

The genus _Ammophila_ is of wide distribution, and its species make vertical tunnels in the ground. The habits of some of the species found in France have been described by Fabre. The Insect does not inhabit the burrow while it is in process of formation, but quits it; and some of the species temporarily close the entry to the incomplete nest with a stone. The tunnel is a simple shaft with a single cell at its termination; this is stored with caterpillars, the different species of _Ammophila_ selecting different grubs for the purpose. _A. hirsuta_ hibernates in the perfect state, and carries on its work in the spring; it chooses a single larva of considerable size belonging to one of the nocturnal Lepidoptera, and this it paralyses by a series of about nine stings, of which one is implanted in each segment from the first thoracic ring backwards; it forms the burrow only after the food to be placed therein has been obtained. The caterpillar used is subterranean in habit, and the _Ammophila_ detects the larva by some sense, the nature of which appears at present quite uncertain. _A. holosericea_ chooses smaller larvae of the family Geometridae, and uses only one or two stingings to paralyse each larva; several caterpillars are used to provision a single cell, and they are often selected of different colours.

Marchal has also published an important account of the proceedings of _A. affinis_; he confirms Fabre's observations, and even adds to their interest by suggesting that the _Ammophila_ administers special stings for the purpose of paralysing the mandibles of the caterpillar and depriving it of any power of afterwards injuring the larva that will feed on it. He thinks the mother-_Ammophila_ herself profits by appropriating an exudation from the victim.

Some species of Sphegides have the curious habit of choosing {112}the interiors of human habitations as the spots most suitable for the formation of their own domestic establishments. Fabre has given a charming account of the habits of _Pelopaeus_ (_Sceliphron_) _spirifex_, a species that inhabits the South of Europe, and that forms its nests in the cottages of the peasants. The spot usually selected is a nook in the broad, open fireplace, out of reach of the flames, though not of the smoke; here the _Pelopaeus_ forms a nest of earth, consisting of ten to fifty cells, the material being mud or clay brought in little balls by the aid of the Insect's mandibles; about twenty visits are required in order to complete one cell, so that for the construction of a large nest of fifty cells, about one thousand visits must be made by the Insect. It flies in and out of the house apparently not at all incommoded by the human habitants, or by the fact that the peasant's potage may be simmering on the fire quite close to where the fearless little creature is carrying on its architectural operations. The cells are stored with spiders, of which the wasp has to bring a plentiful supply, so that its operations extend over a considerable period. The prey is captured by the _Pelopaeus_ whilst on the wing, and carried off at once, being probably stung by the wasp during the process of transit; apparently it is killed by the operation, not merely paralysed. Only small spiders are taken by this species, and the larva of the _Pelopaeus_ consumes them in a short time, one by one, before the process of decomposition sets in; the egg, too, is laid on the first spider introduced, and this is of course at the bottom of the cell, so that the spiders are eaten by the wasp's larva in the order in which they were brought to the cell. The cell is sealed up when full, the number of spiders placed in it being on the average about eight. The larva completes its task of consuming the store in about ten days, and then forms a cocoon for its metamorphosis. Two or three generations are produced in a single year, the autumnal one passing eight or nine months in the clay cells, which are lodged in a nook of the peasant's hearth, and exposed to the smoke of his fire during all the months of winter. _Pelopaeus_ (_Sceliphron_) is a genus including many species;[51] several of them are known {113}to be specially attached to the habitations of human beings. Roth has given an account of the habits of _P._ (_Sceliphron_) _laetus_ in Australia; he says that in some parts it is very difficult to keep these wasps out of the houses; the nest is formed of mud, and constructed on the furniture or in any part of a room that suits the fancy of the Insect. This it must be admitted is, according to human ideas, liable to the charge of being very capricious. Roth timed a wasp building its nest, and found that it brought a fresh load of mud every two or three minutes. If the wasp be allowed to complete the nest undisturbed, she does so by adding to the exterior diagonal streaks of mud, so giving to the nest the look of a small piece of the bark of a common acacia. The construction consists of from ten to twenty cells, and when completed is provisioned with spiders for the use of the young. This wasp is much pestered by parasites, some of which prevent the development of the larvae by consuming the spiders intended by the mother-wasp for its young. A fly, of the Order Diptera, is said to follow the wasp when carrying a spider, and to deposit also an egg on the food; as the Dipterous larvae have more rapid powers of assimilation, the _Pelopaeus_ larvae are starved to death; and their mildewed remains may be found in the cell, after their enemies have become fully developed and have flown away. Another parasite is said to eat the wasp-larva, and attains this end by introducing an egg through the mud wall and the cocoon of the wasp—a habit that seems to indicate a _Leucospid_ parasite. _Tachytes australis_, a wasp of the sub-family Larrides also dispossesses this _Pelopaeus_ in a manner we shall subsequently describe. This fragment of natural history from Australia has a special interest, for we find repeated there similar complex biological relations to those existing in the case of the European congeners.

_P._ (_Sceliphron_) _madraspatanus_ is common in the north-west provinces of Hindostan, and is called the "mud-dauber" by the European residents. According to Horne it constructs its cells in the oddest places, but chiefly about the inhabited apartments in houses. It is perfectly fearless when engaged in building: the cells are four to six in number, and are usually provisioned with spiders to the number of about twenty. On one occasion it was observed that green caterpillars were stored instead of {114}spiders. The species is said to be protected by a peculiar odour as well as by its sting; it is also stated that it disguises its edifice when completed by making it look like a dab of mud, and on one occasion "rays of mud were observed round the nest, even more exactly imitating a lump of mud thrown with some force." _P._ (_Sceliphron_) _bilineatus_, formerly thought to be a variety of _P. madraspatanus_, builds its nests in hedges and trees.

SUB-FAM. 2. AMPULICIDES.—_Prothorax long and narrow, forming a neck in front; clypeus beak-like; four submarginal cells, the outer one being complete; metathorax elongate, the posterior part of the metasternum deeply divided to allow a perfect inflection of the abdomen._

[Illustration: Fig. 44—_Ampulex compressa_. Male. East India.]

This is one of the smallest of the divisions of the Sphegidae, but has a very wide distribution, being represented in both the Eastern and Western Hemispheres. It is allied to the Sphegides, but differs by the prolongation of the neck and of the head, and by the articulation between the petiole and thorax being placed on the under surface of the body; the wing-nervures are said to be of inferior importance owing to their frequently differing in individuals of the same species. These Insects appear to be rare in individuals, as well as few in species, and but little has been recorded as to their habits; but it is known that they live on cockroaches. Perkins has given a brief sketch of the habits of _Ampulex sibirica_ that is of great interest, but requires confirmation. He says that this Insect, in West Africa, enters apartments where cockroaches abound, and attacking one, that may probably be four times its own size, succeeds, after a struggle, in stinging it; the cockroach instantly becomes quiet and submissive, and suffers itself to be led away and placed in confinement in some {115}spot such as a keyhole, and in one case was apparently prevented from afterwards escaping, by the wasp carrying some heavy nails into the keyhole. The larva of the _Ampulex_ may be presumed to live on the Blattid, as it is added that dead bodies of the cockroaches are frequently found with the empty cocoon protruding from them. This account, if correct, points to some features in the habits of this Insect that are unique. A remark made by Rothney in reference to the habits of _A._ (_Rhinopsis_) _ruficornis_ seems to indicate some similar instinct on the part of that species; he says, "I also saw two or three of these wasps collar a peculiar cockroach by the antennae and lead it off into a crack in the bark, but as the cockroach reappeared smiling each time, I don't know what was up." The same observer records that this species associates with _Sima rufonigra_, an ant it greatly resembles in appearance, as well as with a spider that is also of similar appearance (Fig. 72). Schurr has given a brief account of the proceedings of _Ampulex compressa_, and his statements also tend to confirm the correctness of Perkins' report. The habits of a species of _Ampulex_ were partially known to Réaumur, who described them on the authority of M. Cossigni. The species is believed to be _A. compressa_, which occurs not only in East India, but also in the island of Bourbon, the locality where M. Cossigni made his observation: his account is, like the others, a mere sketch of certain points observed, the most important of which is that when _Ampulex_ cannot introduce the cockroach into a hole that it has selected as suitable, it bites off some portions of the body in order to reduce the poor Insect to the necessary extent.

From these fragmentary observations it would appear that the sting of the _Ampulex_ has not so powerful a paralysing effect as that of most other Fossores; and that the _Ampulex_ does not form any nest, but takes advantage of suitable holes and crevices to store the victim in; also that it displays considerable ingenuity in the selection of materials with which to block up the cavity in which it has placed the partially incapacitated creature.

The genus _Dolichurus_ is by some entomologists considered the type of a sub-family allied to the Ampulicides; it long consisted of a small and rare European Insect, but some exotic species have recently been added to it. It will probably prove not {116}sufficiently distinct from Ampulicides, although the pronotum is much shorter, but Handlirsch has recently observed that the European species attacks Blattidae as do the normal Ampulicides; and Ferton has recorded that _D. haemorrhous_ lives at the expense of _Loboptera decipiens_, the wasp depositing its egg on the left intermediate femur of the prey. This is placed in a solitary cell, and is entirely consumed by the larva, life being preserved till within a few hours of the end of the repast, which occupies altogether eight days.

SUB-FAM. 3. LARRIDES.—_Hind body not pedicellate, or with only a short pedicel; one spur on the middle tibia; labrum inconspicuous. Marginal cell of the front wings appendiculate,[52] or mandibles excised externally, or both._

This group is by some writers called Tachytides instead of Larrides, as owing to a change of nomenclature _Tachytes_ may now be considered its principal genus. It is in connection with this and the neighbouring sub-families of Sphegidae that some of the greatest taxonomical difficulties exist. We include in Larrides the "_Miscophus_ group" of Kohl.

The species of the genus _Tachytes_ seem to have habits very similar to those of the genus _Sphex_; they form shafts in the earth and provision them with Orthoptera; like the _Sphex_ and other Fossores, they have the habit, when they fly to their tunnel with a victim, of depositing it for a short time on the ground close to the mouth of the burrow while they turn round and enter backwards; and, after doing this they again seize their prey and drag it into the burrow. Fabre availed himself of an opportunity to remove the prey while the Hymenopteron was entering the hole alone; as a result it had to come out again to seek the object; this it soon found, and carried to the hole, relinquishing it again as usual while it turned round; Fabre repeated the operation several times, and always with the same result; the wasp, though it might have kept hold of the victim while it turned, and thus have saved itself from losing the precious object, never did so.

{117}One species of _Tachytes_ in the south of France selects as its prey Orthoptera of the family Mantidae, Insects of a highly ferocious disposition, and provided with most powerful front legs, capable of cutting in two by a single act the body of an aggressor like the _Tachytes_; the latter is, however, by no means dismayed by the arms of its future victim, but hovering above the latter for some time, as if to confuse it, and causing it repeatedly to turn its very mobile head, the _Tachytes_ at last pounces down and instantaneously stings the _Mantis_ in the nerve centre between the formidable arms, which at once are reduced to incapacity; subsequently the _Tachytes_ paralyses each of the other pairs of legs, and then carries off its victim.

[Illustration: Fig. 45.—_Tachytes pectinipes_ ♀. Britain.]

_Larra anathema_ chooses mole-crickets as the viand for its young, and _Tachysphex panzeri_ selects grasshoppers of the family Acridiidae. _Larra pompiliformis_ (= _Tachytes niger_, Fabre) sometimes associates itself with _Sphex flavipennis_ (_? S. maxillosus_, according to Kohl), forming its burrow amidst the works of a colony of that species, and making use, like the _Sphex_, of crickets for provender. This led Fabre to believe that the _Larra_ stole its prey from the _Sphex_, but he has since withdrawn this indictment, and declares that the _Larra_ obtains its crickets by the more honourable, if not more humane, process of catching and stinging them itself. Smith has informed us, on the faith of his own observation, that _L. pompiliformis_ uses both Lepidopterous larvae and grasshoppers for its stores.

_T._ (_Larrada_) _australis_, according to Whittell, plays the part of a burglar, breaking open the cells of _Pelopaeus_ (_Sceliphron_) _laetus_ after they have been completed and stored with spiders; it then takes possession of the cell, and curiously enough the _Pelopaeus_ permits this, although the cell contains its egg and the store of food that is intended for the use of its own young. To us this seems very strange, but it is probable that the _Pelopaeus_ has no idea of the consequences of the intruder's operations; {118}it being one of the strange facts of nature that these highly endowed creatures never even see the offspring for whose welfare they labour with such extraordinary ingenuity and perseverance. Neither can we suppose that they have a conception of it derived from a knowledge of their own individual history; for their very complete metamorphosis is scarcely reconcilable with any such recollection on their part. It may possibly therefore be the case that, having no idea whatever of the offspring, they are equally destitute of any conception that it will be destroyed by the operations of the _Larrada_. However this may be, Whittell informs us that both wasps skirmish about for a little as if each were mistrustful and somewhat afraid of the other; this ends by the _Pelopaeus_ withdrawing its opposition and by the _Larrada_ taking possession of the cell, which it then proceeds to divide into two, using for the purpose of the partition portions of the material of the nest itself; possibly it is only a contraction of the size of the cell, not a true division, that is effected; however this may be, after it is accomplished the _Larrada_ deposits its own egg in the cell, having, it is believed by Whittell, previously destroyed that of the _Pelopaeus_. Judging from what occurs in other species it is, however, more probable that the destruction of the egg or young of the _Pelopaeus_ is carried out by the larva of the _Larrada_ and not by the parent-wasp. From a remark made by Maindron as to the proceedings of _Larrada modesta_, in Ternate, it seems probable that its habits may prove to be similar to those of _L. australis_, for it frequents the nests of _Pelopaeus_ after they have been completed.

SUB-FAM. 4. TRYPOXYLONIDES.—_Differ from Larrides by the inner margin of the eyes being concave, and the marginal cell not appendiculate. (In_ Trypoxylon _there is only one distinct submarginal and one distinct discoidal cell, a second of each being indicated faintly.)_

The nervuration of _Trypoxylon_ is very peculiar, and differs from that of the widely-distributed genus _Pison_, though according to Kohl's views the two may be correctly associated to form this sub-family. The species of _Trypoxylon_ are apparently rather fond of human propinquity, and build clay- or mud-nests in or near houses. _T. albitarse_ has this habit, and is well known in Southern Brazil under the name of "_Marimbouda da casa_"; {119}this Insect, like _Pelopaeus_, stores its nest with spiders, and Peckholt has remarked that however great may be the number of spiders placed by the mother-wasp in a cell, they are all consumed by the larva, none ever being found in the cell after the perfect Insect escapes therefrom. The European _T. figulus_ forms a nest either in bramble-stems or in sandy soil or walls; it makes use of spiders as provisions.

SUB-FAM. 5. ASTATIDES.—_Eyes very large in the male, meeting broadly on the vertex; two spurs on the middle tibia._

[Illustration: Fig. 46—_Astata boops_, male. Britain.]

We have two species of the genus _Astata_ in Britain: one of them—_A. boops_—is known to form burrows in the ground, each of which contains only a single cell; this, it appears, is usually provisioned with bugs of the genus _Pentatoma_, Insects remarkable for their strong and offensive odour. St. Fargeau records that this species also makes use of a small cockroach for forming the food-store: thus exhibiting an unique catholicity in the toleration of the disagreeable; almost the only point of connection between bugs and cockroaches being their disagreeable character. According to Smith, _Oxybelus_, another genus of Fossores, is also used. Authorities are far from agreement as to the validity and relations of the sub-family Astatides. It consists only of the widely-distributed genus _Astata_, with which the North American _Diploplectron_ (with one species) is doubtfully associated.

SUB-FAM. 6. BEMBECIDES.—_Labrum frequently elongate; wing-nervures extending very near to the outer margin; marginal cell of front wing not appendiculate; mandibles not emarginate externally; hind body stout, not pedicellate._

The elongation of the labrum, though one of the most trustworthy of the characters of the Bembecides, cannot be altogether {120}relied on owing to the variation it presents both in this and the allied sub-families. The Bembecides carry their prey to their young tucked underneath their own bodies and hugged to the breast; they affect loose, sandy soils for nidification; make use, in the great majority of the cases where the habits are known, of Diptera for provisions, and give these dead to the young; making repeated visits to supply fresh food to the progeny, which notwithstanding this fact, are distributed in isolated burrows.

[Illustration: Fig. 47.—_Bembex rostrata_ ♂. Europe.]

One of the most interesting of Fabre's studies of the instincts of Hymenoptera is devoted to _Bembex rostrata_. The Bembecides have the habit of forming their nests in the ground in wide expanses of sand, and of covering them up, they leave them so that there appears to be absolutely nothing by which the exact position of the nest can be traced; nevertheless the _Bembex_ flies direct to it without any hesitation. How necessary it is to these Insects to possess this faculty of finding their nests will be understood when we recall that the _Bembex_ does not provision its nest once and for all, but supplies the young at first with only insufficient food, and has therefore to return at daily, or other intervals, with a fresh store of provisions. The burrow is made in the sand by means of the fore-legs; these work with such rapidity and skill that a constant stream of sand flows out behind the Insect while it is engaged in the act of excavation. The nest or cell in which the larva is to live, is formed by this process of digging; but no fastening together of the material occurs, nor does any expedient seem to be resorted to, other than that of making a way through the sand by clearing out all the pieces of stick or stone that might diminish facility of access. The cell being formed, the _Bembex_ leaves the spot in search of prey, and when it has secured a victim in the shape of a two-winged fly, it returns therewith to the burrow, and the booty is placed therein, an egg being deposited on it. The wasp then leaves the burrow, disguising, however, the spot where it is situate, and flies away; to proceed possibly with the formation {121}of other burrows.[53] In the course of twenty-four hours the egg hatches, and the larva in two or three days completely devours the stock provided for it. The mother-wasp then returns with another fly—this time probably a larger one—penetrates rapidly to the bottom of the burrow, and again retreats, leaving the second stock of provisions for the benefit of the greedy larva. These visits of supply are repeated with increased frequency, as the appetite of the larva for the benefit of which they are made increases with its growth. During the fourteen or fifteen days that form this portion of the life-cycle, the single larva is supplied with no less than fifty to eighty flies for food. To furnish this quantum, numerous visits are made to each burrow, and as the mother _Bembex_ has several burrows—though how many does not appear to be known—her industry at this time must be very great. All the while, too, a great danger has to be avoided, for there is an enemy that sees in the booty brought by the _Bembex_ to its young, a rich store for its own progeny. This enemy is a feeble, two-winged fly of the family Tachinidae and the genus _Miltogramma_; it hangs about the neighbourhood of the nests, and sooner or later finds its opportunity of descending on the prey the _Bembex_ is carrying, choosing for its purpose a moment when the _Bembex_ makes a brief delay just at the mouth of the burrow; then down comes the _Miltogramma_ and lays one, two, or three eggs on some portion of the booty that may be projecting from beneath the body of the wasp. This latter carries in the food for its own young, but thus introduces to the latter the source of its destruction, for the _Miltogramma_ larvae eat up the supply of food intended for the _Bembex_ larvae, and if there be not enough of this provender they satisfy their voracity by eating the _Bembex_ larva itself. It is a remarkable fact that notwithstanding the presence of these strange larvae in the nest the mother _Bembex_ continues to bring food at proper intervals, and, what is stranger still, makes no effort to rid the nest of the intruders: returning to the burrow with a supply of food she finds therein not only her legitimate offspring, a single tenant, but several others, strangers, it may be to the number of twelve; although she would have no difficulty in freeing the nest from this band of little brigands, she makes no attempt to do so, but continues to bring the {122}supplies. In doing so she is fulfilling her duty; what matters it that she is nourishing the enemies of her race? Both race and enemies have existed for long, perhaps for untold periods of time, why then should she disturb herself, or deviate from her accustomed range of duties? Some of us will see in such proceedings only gross stupidity, while others may look on them as sublime toleration.

The peculiar habits of _Bembex rostrata_ are evidently closely connected with the fact that it actually kills, instead of merely paralysing, its prey; hence the frequent visits of supply are necessary that the larvae may have fresh, not putrefying, food; it may also be because of this that the burrow is made in a place of loose sand, so that rapid ingress may be possible to the _Bembex_ itself, while the contents of the burrow are at the same time protected from the inroads of other creatures by the burrow being filled up with the light sand. Fabre informs us that the _Bembex_ larva constructs a very remarkable cocoon in connection with the peculiar nature of the soil. The unprotected creature has to pass a long period in its cocoon, and the sandy, shifting soil renders it necessary that the protecting case shall be solid and capable of keeping its contents dry and sound. The larva, however, appears to have but a scanty supply of silk available for the purpose of constructing the cocoon, and therefore adopts the device of selecting grains of sand, and using the silk as a sort of cement to connect them together. For a full account of the ingenious way in which this difficult task is accomplished the reader should refer to the pages of Fabre himself. Bembecides appear to be specially fond of members of the Tabanidae (or Gad-fly family) as provender for their young. These flies infest mammals for the purpose of feasting on the blood they can draw by their bites, and the Bembecides do not hesitate to capture them while engaged in gratifying their blood-thirsty propensities. In North America a large species of Bembecid sometimes accompanies horsemen, and catches the flies that come to attack the horses; and Bates relates that on the Amazons a Bembecid as large as a hornet swooped down and captured one of the large blood-sucking Motuca flies that had settled on his neck. This naturalist has given an account of some of the Bembecides of the Amazons Valley, showing that the habits there are similar to those of their European congeners.

{123}_Sphecius speciosus_ is a member of the Stizinae, a group recognised by some as a distinct sub-family. It makes use, in North America, of Insects of the genus _Cicada_ as food for its young. Burrows in the ground are made by the parent Insect; the egg is deposited on the _Cicada_, and the duration of the feeding-time of the larva is believed to be not more than a week; the pupa is contained in a silken cocoon, with which much earth is incorporated. Riley states that dry earth is essential to the well-being of this Insect, as the _Cicada_ become mouldy if the earth is at all damp. As the _Cicada_ is about twice as heavy as the _Sphecius_ itself, this latter, when about to take the captured burden to the nest, adopts the plan of climbing with it to the top of a tree, or some similar point of vantage, so that during its flight it has to descend with its heavy burden instead of having to rise with it, as would be necessary if the start were made from the ground.

SUB-FAM. 7. NYSSONIDES.—_Labrum short; mandibles entire on the outer edge; hind body usually not pedicellate; wing with the marginal cell not appendiculate._

This group has been but little studied, and there is not much knowledge as to the habits of the species. It is admitted to be impossible to define it accurately. It is by some entomologists considered to include _Mellinus_, in which the abdomen is pedicellate (Fig. 48), while others treat that genus as forming a distinct sub-family, Mellinides. Kohl leaves _Mellinus_ unclassified. Gerstaecker has called attention to the fact that many of the Insects in this group have the trochanters of the hind and middle legs divided: the division is, as a rule, not so complete as it usually is in Hymenoptera Parasitica; but it is even more marked in some of these Nyssonides than it is in certain of the parasitic groups.

_Mellinus arvensis_ is one of our commonest British Fossores, and we are indebted to the late F. Smith for the following account of its habits: "It preys upon flies, and may be commonly observed resorting to the droppings of cows in search of its prey; it is one of the most wary and talented of all its fraternity; were it at once to attempt, by a sudden leap, to dart upon its victim, ten to one it would fail to secure it; no, it does no such thing, it wanders about in a sort of innocent, unconcerned way, amongst {124}the deluded flies, until a safe opportunity presents itself, when its prey is taken without any chance of failure; such is its ordinary mode of proceeding. At Bournemouth the flies are more active, more difficult to capture, or have they unmasked the treacherous _Mellinus?_ and is it found necessary to adopt some fresh contrivance in order to accomplish its ends? if so, it is not deficient in devices. I noticed once or twice, what I took to be a dead specimen of _Mellinus_, lying on patches of cow-dung; but on attempting to pick them up off they flew; I at once suspected the creature, and had not long to wait before my suspicions were confirmed. Another, apparently dead fellow, was observed; and there, neither moving head or foot, the treacherous creature lay, until a fine specimen of a Bluebottle ventured within its grasp, when, active as any puss, the _Mellinus_ started into life, and pounced upon its victim."

[Illustration: Fig. 48.—_Mellinus arvensis_ ♀. Britain.]

Lucas states that in the north of France _Mellinus sabulosus_ provisions its nest with Diptera, which it searches for on the flowers of Umbelliferae, and then carries to its nest. This is a burrow in the earth, and when it is reached the Hymenopteron deposits its Insect burden for a moment on the ground while it turns round in order to enter the burrow backwards. The same writer states that two varieties of this Insect live together—or rather in the same colonies—and make use of different species of Diptera, even of different genera, as food for their young. These Diptera are stung before being placed in the nest. The stinging does not kill the Insect, however, for Lucas was able to keep one specimen alive for six weeks after it had passed this trying ordeal.

SUB-FAM. 8. PHILANTHIDES.—_Labrum small; anterior wings with three complete submarginal cells; hind body constricted at the base but not so as to form a slender pedicel._

This sub-family contains Insects resembling wasps or Crabronides in appearance, and is, as regards the pronotal structure, {125}intermediate between the two great divisions of the Fossores, for the pronotal lobe extends nearly or quite as far back as the tegulae, and in _Philanthus_ the two come into almost actual contiguity.

The species of the genus _Cerceris_ are numerous in Europe, and several of them are known to make burrows in the ground, and store them with beetles for the benefit of the future larvae. The beetles chosen differ in family according to the species of _Cerceris_; but it appears from the observations of Fabre and Dufour that one kind of _Cerceris_ never in its selection goes out of the limits of a particular family of beetles, but, curiously enough, will take Insects most dissimilar in form and colour provided they belong to the proper family. This choice, so wide in one direction and so limited in another, seems to point to the existence of some sense, of the nature of which we are unaware, that determines the selection made by the Insect. In the case of our British species of _Cerceris_, Smith observed _C. arenaria_ carrying to its nest Curculionidae of very diverse forms; while _C. labiata_ used a beetle—_Haltica tabida_—of the family Chrysomelidae.

[Illustration: Fig. 49.—_Philanthus triangulum_ ♂. Britain.]

The beetles, after being caught, are stung in the chief articulation of the body, that, namely, between the pro- and mesothorax. _Cerceris bupresticida_ confines itself exclusively to beetles of the family Buprestidae. It was by observations on this Insect that Dufour first discovered the fact that the Insects stored up do not decay: he thought, however, that this was due to the liquid injected by the wasp exercising some antiseptic power; but the observations of Fabre have shown that the preservation in a fresh state is due to life not being extinguished; the stillness, almost as if of death, being due to the destruction of the functional activity of the nerve centres that govern the movements of the limbs.

{126}It has long been known that some species of _Cerceris_ prey on bees of the genus _Halictus_, and Marchal has recently described in detail the proceedings of _C. ornata_. This Insect catches a _Halictus_ on the wing, and, holding its neck with the mandibles, bends her body beneath it, and paralyses it by a sting administered at the front articulation of the neck. The _Halictus_ is subsequently more completely stunned or bruised by a process of kneading by means of the mandibles of the _Cerceris_. Marchal attaches great importance to this "malaxation"; indeed, he is of opinion that it takes as great a part in producing or prolonging the paralysis as the stinging does. Whether the malaxation would be sufficient of itself to produce the paralysis he could not decide, for it appears to be impossible to induce the _Cerceris_ to undertake the kneading until after it has reduced the _Halictus_ to quietude by stinging.

Fabre made some very interesting observations on _Cerceris tuberculata_, their object being to obtain some definite facts as to the power of these Insects to find their way home when removed to a distance. He captured twelve examples of the female, marked each individual on the thorax with a spot of white paint, placed it in a paper roll, and then put all the rolls, with their prisoners, in a box; in this they were removed to a distance of two kilometres from the home and then released. He visited the home five hours afterwards, and was speedily able to assure himself that at any rate four out of the twelve had returned to the spot from whence they had been transported, and he entertained no doubt that others he did not wait to capture had been equally successful in home-finding. He then commenced a second experiment by capturing nine examples, marking each with two spots on the thorax, and confining them in a dark box. They were then transported to the town of Carpentras, a distance of three kilometres, and released in the public street, "in the centre of a populous quarter," from their dark prison. Each _Cerceris_ on being released rose vertically between the houses to a sufficient height, and then at once passed over the roofs in a southerly direction—the direction of home. After some hours he went back to the homes of the little wasps, but could not find that any of them had then returned; the next day he went again, and found that at any rate five of the _Cerceris_ liberated the previous day were then at home. This record is of considerable {127}interest owing to two facts, viz. that it is not considered that the _Cerceris_ as a rule extends its range far from home, and that the specimens were liberated in a public street, and took the direction of home at once.

_Philanthus apivorus_ is one of the best known of the members of this sub-family owing to its habit of using the domestic honey-bee as the food for its offspring. In many respects its habits resemble those of _Cerceris ornata_, except that the _Philanthus_ apparently kills the bee at once, while in the case of the _Cerceris_, the _Halictus_ it entombs does not perish for several days. The honey-bee, when attacked by the _Philanthus_, seems to be almost incapable of defending itself, for it appears to have no power of finding with its sting the weak places in the armour of its assailant. According to Fabre, it has no idea of the _Philanthus_ being the enemy of its race, and associates with its destroyer on amicable terms previous to the attack being made on it. The _Philanthus_ stings the bee on the under-surface of the mentum; afterwards the poor bee is subjected to a violent process of kneading, by which the honey is forced from it, and this the destroyer greedily imbibes. The bee is then carried to the nest of the _Philanthus_. This is a burrow in the ground; it is of unusual depth—about a yard according to Fabre—and at its termination are placed the cells for the reception of the young; in one of these cells the bee is placed, and an egg laid on it: as the food in this case is really dead, not merely in a state of anæsthesia, the _Philanthus_ does not complete the store of food for its larvae all at once, but waits until the latter has consumed its first stock, and then the mother-wasp supplies a fresh store of food. In this case, therefore, as in _Bembex_, the mother really tends the offspring.

SUB-FAM. 9. MIMESIDES.—_Small Insects with pedicellate hind body, the pedicel not cylindric; mandibles not excised externally; inner margin of eyes not concave; middle tibia with one spur; wings with two, or three, submarginal cells._

Mimesides is here considered to include the Pemphredonides of some authors. Mimesides proper comprises but few forms, and those known are small Insects. _Psen concolor_ and _P. atratus_ form their nests in hollow stems, and the former provisions its nest with Homopterous Insects of the family Psyllidae. Little {128}information exists as to their habits; but Verhoeff states that the species of _Psen_—like members of the Pemphredoninae—do not form cocoons.

The Pemphredonine subdivision includes numerous small and obscure Insects found chiefly in Europe and North America (Fig. 51, _P. lugubris_); they resemble the smaller black species of Crabronides, and are distinguished from them chiefly by the existence of at least two complete, submarginal cells on the anterior wing instead of one.

[Illustration: Fig. 50.—_Mimesa bicolor_ ♂. Britain.]

The species of _Passaloecus_ live in the burrows that they form in the stems of plants; _Pemphredon lugubris_ frequents the decayed wood of the beech. The larva and pupa of the latter have been described by Verhoeff; no cocoon is formed for the metamorphosis. Both these genera provision their nests with Aphidae. This is also the case with _Stigmus pendulus_, but the burrows of this species form a complex system of diverticula proceeding from an irregular main channel formed in the pithy stems of bushes. _Cemonus unicolor_, according to Giraud, forms its burrows in bramble-stems, but it also takes advantage, for the purposes of nidification, of the abandoned galls of _Cynips_, and also of a peculiar swelling formed by a fly—_Lipara lucens_—on the common reed, _Arundo phragmites_. This species also makes use of Aphidae, and Verhoeff states that it has only an imperfect instinct as to the amount of food it stores.

[Illustration: Fig. 51.—_Pemphredon lugubris_ ♀. Britain.]

SUB-FAM. 10. CRABRONIDES.—_Pronotum short, front wing with one complete submarginal and two discoidal cells: hind body {129}variable in form, pedicellate in some abnormal forms, but more usually not stalked._

The Crabronides (_Vespa crabro_, the hornet, is not of this sub-family) are wasp-like little Insects, with unusually robust and quadrangular head. They frequently have the hind tibiae more or less thickened, and the clypeus covered with metallic hair. It appears at present that they are specially attached to the temperate regions of the northern hemisphere, but this may possibly be in part due to their having escaped attention elsewhere. In Britain they form the most important part of the fossorial Hymenoptera, the genus _Crabro_ (with numerous sub-genera) itself comprising thirty species. The males of some of the forms have the front tibiae and tarsi of most extraordinary shapes. They form burrows in dead wood, or in pithy stems, (occasionally in the earth of cliffs), and usually store them with Diptera as food for the larvae: the wings and dried portions of the bodies of the flies consumed by Crabronides are often exposed to view when portions of old wood are broken from trees.

[Illustration: Fig. 52.—_Crabro cephalotes_ ♀. Britain.]

The genus _Oxybelus_ is included by some systematists, but with doubt, in this sub-family; if not placed here, it must form a distinct sub-family. It has the metathorax spinose, and the sub-marginal and first discoidal cells are not, or are scarcely, separated.

_Crabro leucostomus_ has been observed by Fletcher to form cells for its larvae in the soft wood of broken willows: the food stored therein consists of two-winged flies of the family Dolichopodidae. This _Crabro_ is parasitised by an Ichneumonid of the genus _Tryphon_, and by a two-winged fly of uncertain genus, but belonging to the family Tachinidae. The metamorphoses of _Crabro chrysostomus_ have been briefly described by Verhoeff: the food stored consists of Diptera, usually of the family {130}Syrphidae; the larva spins an orange-red cocoon, passes the winter therein, and assumes the pupal form in the spring; there is, he says, a segment more in the female pupa than there is in the male.

The species of the sub-genus _Crossocerus_ provision their nests with Aphididae, but _C. wesmaeli_ makes use, for the purpose, according to Ferton, of an elegant little fly of the family Tipulidae; according to Pissot this same wasp also makes use of a species of _Typhlocyba_, a genus of the Homopterous division of Rhynchota. Supposing there to be no mistake as to this latter observation, the choice of Diptera and of Homoptera by the same species indicates a very peculiar habit.

_Fertonius_ (_Crossocerus_) _luteicollis_ in Algeria forms cells at a slight depth in sandy soil, and provisions them with ants. The ant selected is _Tapinoma erraticum_, and the individuals captured are the wingless workers. The mode of hunting has been described by Ferton; the wasp hovers over one of the ant-paths at a distance of a few millimetres only above the surface, and when an ant that is considered suitable passes, the _Fertonius_ pounces on it, stings it, and carries it off to the burrow; forty or fifty ants are accumulated in a cell, the egg is laid in the heap of victims about one-third of the depth from the bottom; the resulting larva sucks the ants one by one, by attaching itself to the thorax behind the first pair of legs. There is a very interesting point in connection with the habits of this species, viz. that the ants are not only alive, but lively; they have, however, lost the power of co-ordinating the movements of the limbs, and are thus unable to direct any attack against the feeble larva. Ferton thinks there are three generations of this species in a single year.

* * * * *

Note.—In a note on p. 99 we have mentioned the new publication of Mr. and Mrs. Peckham on the habits of Fossores. We may here add that it contains much fresh information on these Insects, together with criticisms of the views of Fabre and others. One of the points most noteworthy is that they have observed _Crabro stirpicola_ working night and day for a period of forty-two consecutive hours. They made experiments on _Bembex spinolae_ with a view of ascertaining whether the female provisions two nests simultaneously; as the result they think this improbable. If the female Bembecid make nests only consecutively, it is clear it must have but a small fecundity. The larval life extends over about fifteen days; and if we allow three months as the duration of life of a female, it is evident that only about six young can be produced in a season.

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