Part 19

De Geer states that he had seen them of the length of two feet[1015]; but they vary considerably in this respect. In ants, in which Gould detected them, he states their length to be not more than half an inch[1016]. In caterpillars, which they sometimes infest, they are longer; in that of _Notodonta Ziczac_, De Geer found one three inches and a half long[1017]; and Rösel three, of six inches, in that of _Deilephila Euphorbiæ_[1018]; and in _Phalangium cornutum_, according to Latreille, they extend to more than seven inches[1019]. In the larva of a _Phryganea_ L. the author first named found one which was more than a foot long, corresponding exactly with the _Gordius aquaticus_ of Linné; being forked at one extremity, brown above, gray below, and black at each end[1020]. These animals _appear_ to die as soon as they leave the body[1021] they have preyed upon; except this happens in water, when their activity has no repose. In this element they give their bodies every possible inflexion, often tying themselves in knots in various places, interlacing and twisting themselves in a hundred different ways; so that when confined in the body of an insect, from their extreme suppleness and power of contortion they find sufficient space wherein to pack their often enormous length[1022]. Linné makes one of their habitats clay; and Mr. W. S. MacLeay finds them very common at Putney in clay at the bottom of pools.

Dr. Matthey asks--How does the _Gordius_ get into _Acrida viridissima_[1023]? And De Geer--Why do they die after having quitted a caterpillar? and where do they perpetuate their species[1024]? These questions, without further observations, cannot easily be answered. However, it may be supposed that carnivorous insects, such as _Harpali_, &c. may swallow them when found apparently dead in clay, where the water has been evaporated, or when they have been ejected by other insects; and they may revive in their bodies, as Dr. Matthey found them to do in water. It is not difficult to conjecture that the larvæ of _Phryganeæ_ may meet with them when young in the water, and sometimes unluckily swallow them with their food. Why they become as dead when they emerge from their prey we cannot at present conjecture; but no doubt to answer some wise purpose;--in rainy seasons they probably revive and get into little hollows full of rain-water. Upon De Geer's last question--How they perpetuate their species--at present I can offer no conjecture.

I am, &c.

FOOTNOTES:

[918] _Ps._ civ. 29.

[919] _Hist. Animal._ l. viii. c. 27.

[920] _The Principles of Botany and of Vegetable Physiology_, § 310-353.

[921] Dr. Leach, from a communication of Sir Joseph Banks, has given a very interesting history of a spider which, having lost five of its legs, from a web-weaver had become a hunter; these legs it afterwards reproduced, though shorter than the others. _Linn. Trans._ xi. 393. Comp. _N. Dict. d'Hist. Nat._ ii. 282.

[922] VOL. I. p. 55--.

[923] VOL. II. p. 166--.

[924] Huber _Abeilles_ ii. 409.

[925] _N. Dict. d'Hist. Nat._ i. 42.

[926] De Geer i. 72--.

[927] Reaum. iv. 342.

[928] _Naturf._ xii. 224. _t._ v. _f._ 8.

[929] _Naturf._ xvi. _t._ iv. _f._ 1-3.

[930] Huber _Fourmis_, 174. note 1.

[931] VOL. II. p. 365.

[932] _N. Dict. d'Hist. Nat._ i. 42.

[933] De Geer vi. 75. Latr. _Hist. Nat._ xiv. 371.

[934] Jacquin _Collectan._ iii. _t._ xxiii. _f._ 7.

[935] De Geer _ubi supr._

[936] Dr. Bevan asserts (_The Honey-bee_, 197) "that we have no evidence that pollen constitutes any part of the food of _adult_ bees." Had he consulted Reaumur (v. 418) he would have found that this great man examined the proceedings of a bee with a magnifying glass, and distinctly saw her devour very deliberately the masses of pollen on her hind legs. He says also (Ibid. 419.) that if the stomach and intestines are opened, they will be found filled with that substance.

[937] Schirach _Hist._ &c. 54. Reaum. v. 713. _N. Dict. d'Hist. Nat._ i. 42.

[938] _N. Dict. d'Hist. Nat._ i. 42. Schirach _Hist._ 56.

[939] Latr. _Hist. Nat._ xiv. 163--. _N. Dict. d'Hist. Nat._ iv. 134--.

[940] _Œuvr._ ii. 48--.

[941] Lesser L. ii. 121.

[942] _Synops. Meth. Fung._ 687. _g._ 63. _n._ 1, 2.

[943] _Ibid._ 4. _g._ 1. _n._ 4.

[944] VOL. III. p. 335--.

[945] VOL. I. p. 267--.

[946] _Mon. Ap. Angl._ ii. 111. _Linn. Trans._ xi. 90--.

[947] Reaum. ii. 439.

[948] _Ibid._ 415. Mouffet 57.

[949] _Hist. Ins._ Præf. xv.

[950] _Cat. Cant._ 137.

[951] See above, p. 162--.

[952] Reaum. vi. 306.

[953] _Fn. Suec._ 1626.

[954] _Linn. Trans._ iii. 26.

[955] De Geer i. 608. Linné has made a mistake with regard to the Ichneumon here alluded to, in calling De Geer's saltatorious Ichneumon _I. Muscarum_, and referring for it to _t._ xxxii. _f._ 19, 20 of that author; whereas the Ichneumon that preys upon the aphidivorous flies does not jump, and is figured by De Geer 605. _t._ xxxiv. _f._ 26-29. The jumping one feeds on the larva of a _Coccinella_.

[956] Vallisnieri _Lettere_, &c. 80.

[957] Reaum. vi. 296--.

[958] Linné evidently has described another species under _I. Ovulorum_, in _Fn. Suec._ 1644.

[959] De Geer i. 593--.

[960] _N. Dict. d'Hist. Nat._ vi. 10.

[961] Geoffr. _Hist. Ins. Par._ ii. 361.

[962] _Linn. Trans._ v. 102--.

[963] PLATE XX. FIG. 22. _a._

[964] De Geer ii. 850--.

[965] Reaum. ii. 444--.

[966] De Geer ii. 863--.

[967] Panzer _Fn. Germ. Init._ lxxii. 4.

[968] De Geer, i. 583--. ii. 822--. 907.

[969] Reaum. vi. 312.

[970] Leeuwenh. _Epist._ Oct. 6, 1700. De Geer ii. 869.

[971] _Ibid._ i. 604.

[972] Rai. _Hist. Ins._ 259--.

[973] See above, p. 217; and VOL. I. p. 356.

[974] _Ibid._ 348.

[975] Reaum. vi. 303--.

[976] Reaum. ii. 454--.

[977] De Geer ii. 879--.

[978] _N. Dict. d'Hist. Nat._ xvii. 513.

[979] De Geer vi. 411--.

[980] VOL. I. p. 172.

[981] _Linn. Trans._ iv. 236.

[982] VOL. I. p. 50--. 170--. Since that Volume of the present Edition was printed, Say's account of the Hessian Fly has been met with, where he distinguishes it by the above name. (_Journal of the Acad. of Nat. Sciences of Philadelphia_ 1817.) The Ichneumon he calls _Ceraphron Destructor_.

[983] De Geer, i. 605. This, as before observed, is not the _I. Muscarum_ of Linné; but it ought to have that name, and the other instead to be named, _I. Coccinellæ_.

[984] _Ent. Carn._ 760, 761.

[985] De Geer i. 587.

[986] _Ibid._ ii. 876.

[987] Reaum. ii. 417--.

[988] Reaum. ii. 419--.

[989] De Geer i. 583--.

[990] _Ibid._ ii. 884.

[991] See above, p. 164.

[992] Reaum. vi. 312.

[993] VOL. I. p. 99.

[994] De Geer _ubi supr._

[995] _Ibid._ 883.

[996] _Linn. Fn. Suec._ 1609.

[997] Reaum. ii. 443. De Geer i. 196--, 550--. vi. 24.

[998] Reaum. ii. 440--.

[999] VOL. I. p. 99.

[1000] Ibid. 84, 97.

[1001] VOL. I. p. 163. note^c. VOL. III. p. 162. note^b.

[1002] De Geer v. 8--.

[1003] _Naturf._ xxiii. _t._ i. _f._ 8.

[1004] _N. Dict. d'Hist. Nat._ xx. 110--.

[1005] _Ent. Carn._ 1052-4.

[1006] _Hister_ particularly.

[1007] De Geer vii. 126--.

[1008] De Geer vii. 144--.

[1009] Lamarck _Anim. sans Vert._ iii. 196.

[1010] De Geer ii. 554--. Pictet _Bibliotheq. Univers._ num. ult.

[1011] The existence of this animal has been satisfactorily ascertained by M. de Blainville, who had a specimen, extracted from a human body, sent him by M. Girard, a surgeon of Guadaloupe.

[1012] De Geer ii. 555.

[1013] Matthey _ubi supr._

[1014] _Philos. Trans._ 1823. 8. _t._ i. ii.

[1015] De Geer ii. 556.

[1016] Gould _Ants_, 63.

[1017] De Geer i. 551.

[1018] Rösel I. iii. 20.

[1019] Latr. _Fourmis_, 373.

[1020] De Geer ii. _ubi supr._ _t._ xiv. _f._ 12-14.

[1021] _Ibid._ i. 553.

[1022] Ibid. ii. 556. _t._ xiv. _f._ 12, 13.

[1023] _Ubi supra._

[1024] De Geer i. 553.

LETTER XLV.

_SENSES OF INSECTS._

At first one would think that the _senses_ of insects might be described in very few words, and scarcely afford matter for a separate letter; but when we find that physiologists are scarcely yet agreed upon this subject, and that the use of some of their organs, which appear to be organs of sensation, has not yet been satisfactorily ascertained--we shall not wonder that it requires more discussion than at the first blush we were aware of. In treating on this head I shall first say something on the senses in _general_, and then confine myself to those of insects.

Touch, taste, smell, hearing, and sight, I need not tell you, is the usual enumeration of the senses: but as the term includes every means of communication with the external world, the list perhaps might be increased; and there is ground for thinking that the number _seven_, so signalized as a _sacred_ number[1025], may also here have place. Dr. Virey, an eminent physiologist, whose sentiments on various subjects I have before noticed with approbation[1026], appears to be of opinion that there are really _seven_ senses; which he divides into those that are altogether _physical_, and those that are more connected with the _intellect_. The first of these divisions contains _four_ senses,--touch, love, taste, and smell;--the second _three_,--hearing, sight, and the internal sense of thought, or the brain[1027]. That he is right in adding _love_ to the list seems to me evident, because it is as distinct from _touch_, as _smelling_ and _taste_ are. With regard to the other, though it may be expected that there should be a transitive sense connecting the intellect (if I may so speak) with the external organ of sense, and as a medium by which the former can receive the notices of the external world furnished by the latter; yet it seems improper to make the _entire brain_ itself a _sense_. We know that the agent between the common sensory and the sense is the consciousness or _perception_ of the impression. "Seeing we may see and not _perceive_, and hearing we may hear and not _understand_." The picture may be painted upon the retina of the eye, the sound may strike upon the tympanum of the ear; but neither the one nor the other be received by the intellect, unless the internal power or faculty of perception be in action and mediate between them. This is what I mean by the _internal sense_, which, to use a term of Mr. W. S. MacLeay's[1028], is _osculant_ between intellect and sense, or forms the transit from one group of powers to the other.

Of the ordinary senses, _sight_ holds the first rank: it can dart to the region of the stars, and convey by the perceiving sense, to the sensory, ideas of innumerable objects. Next in rank is _hearing_, which can receive sounds from a great distance; but the ideas it remits are confined only to one object, the variations of tones. In the other organs the sensitive power is much more confined. There is another difference between the intellectual and physical senses:--the former are the only ones that receive and convey sensations of the beautiful and sublime; of harmony and discord,--the latter, though they minister more to our sensual enjoyments, add little to our intellectual; and therefore too devoted an indulgence in them debases our nature, and levels us with the brutes, which use their eyes and ears only for information, not for pleasure[1029].

In man the ordinary five senses are usually in their greatest perfection, although in some animals particular senses have a greater range. The Vertebrates in general are also gifted with the same number, though there are some exceptions. But in the _Invertebrates_ they are seldom to be met with all together in the same object. The _Cephalopods_ have no _smell_. Several _Gasteropods_ can neither _hear_ nor _see_. The animals of bivalve shells have neither eyes, nor ears, nor smell; and the zoophytes and the races below them have, it is affirmed, only the single sense of _touch_, which in them is so extremely delicate as to be acted upon even by _light_[1030].

Not so our insects. These, there is good reason to believe, possess all the ordinary senses. That they can _see_, _touch_, _taste_, and _smell_, no one denies. Linné and Bonnet, however, thought them deprived of _hearing_[1031]; but numerous observations prove the contrary. That they hear in their _larva_ state, is evident from facts stated by the latter physiologist. He found that the sound of his voice evidently affected some caterpillars; which he attributes, but surely without reason, to the delicacy of their sense of touch: at another time, when some caterpillars of a different species were moving swiftly, he rang a small bell; upon which they instantly stopped and moved the anterior part of their body very briskly[1032]. That they possess this faculty in their _imago_ state is confirmed still more strongly by facts. I once was observing the motions of an _Apion_ under a pocket microscope: on seeing me it receded. Upon my making a slight but distinct noise, its antennæ started: I repeated the noise several times, and invariably with the same effect. A _Harpalus_, which I was holding in my hand, answered the sound in the same manner repeatedly. Flies, I have observed, at brisk and distinct sounds move all their legs; and spiders will quit their prey and retire to their hiding places. Insects that live in society give notice of intended movements, or assemble their citizens for emigration by a certain _hum_[1033]. But the most satisfactory proof of the hearing of these animals is to be had from those _Orthoptera_ and _Hemiptera_ whose males are vocal. Brunelli kept and fed several males of _Acrida viridissima_ (a grasshopper with us not uncommon) in a closet, which were very merry, and continued singing all the day; but a rap at the door would stop them instantly. By practice he learned to imitate their chirping: when he did this at the door, at first a few would answer him in a low note, and then the whole party would take up the tune and sing with all their might. He once shut up a male in his garden, and gave the female her liberty; but as soon as she heard the male chirp, she flew to him immediately[1034].

But although physiologists are for the most part agreed that insects have the ordinary five senses of vertebrate animals, yet a great variety of opinions has obtained as to their external organs; so that it has been matter of doubt, for instance, whether the _antennæ_ are for smell, touch, or hearing; and the _palpi_ for smell, taste, or touch. Nor has the question, as it appears to me, been satisfactorily decided: for though it is now the most general opinion that the primary use of antennæ is to _explore_ as _tactors_, yet by the most strenuous advocates of this opinion they are owned not to be _universally_ so employed; so that granting this to be _one_ of their principal functions, yet it seems to follow that there may be _another_ common to them all, which of course would be their _primary_ function. We are warned, however, not to lay any stress upon the argument to be drawn from analogy; and told that we might as well dispute about the identity of the nose of a man, the proboscis of the elephant, the horn of the rhinoceros, the crest of the cock, or the beak of the toucan[1035]. But this is merely casting dust in our eyes: for though three of these are _nasal_ organs, bearing _nostrils_; the two others have no relation to the question, the horn of the rhinoceros and the crest of the cock being merely _appendages_, and have no more analogy to the nose and nostrils, which co-exist with them, than they have to the eyes or ears. I have on a former occasion observed, that a gradual change sometimes takes place in the functions of particular organs; but still, generally speaking, this observation regards _secondary_ functions--the _primary_ usually remaining untouched. We may say, for instance, with regard to the primary use of the _legs_ of animals, that it is locomotion; while the secondary is either walking, running, jumping, flying, or swimming, according to the circumstances and nature of the animal. Thus the _fore-legs_ of the _Mammalia_, in _birds_ become _wings_, and both pair in _fish_ are changed to _fins_. Observe, I do not say _always_ and invariably, but in most cases,--that analogous parts have analogous uses, at least as far as _primary_ uses are concerned. When, therefore, we cannot have demonstrative evidence concerning the function of an organ discoverable in any animal, we may often derive satisfactory probable arguments from the analogies observable in their structure compared with that of other animals, concerning the nature of whose organs we have no doubt. In fact, the chief evidence we have with regard to the office of the organs of sense in the animals immediately below ourselves, is that of analogy;--because _we_ see with our eyes, hear with our ears, &c., we conclude, with reason, that _they_ do the same.

In inquiring therefore into what may be the most general use of the antennæ of insects, I shall endeavour to discover whether there is any part in the higher animals to which they may be deemed to exhibit any analogy. And here I must refer you to what I have said on a former occasion upon the present subject; where I made it evident, I hope, that the great bulk of the parts and organs of insects, in this

## particular differing from the majority of Invertebrates, are, some

in one respect, some in another, and some in many, really analogous to those of the higher animals[1036]; and that a great many of them, though varying in their structure, have the same functions. Thus the analogues of the _eyes_ of Vertebrates are for _seeing_; of the _jaws_ for _masticating_; of the _lips_ for _closing_ the _mouth_; of the _legs_ for _walking_, &c. We have seen also very recently, that a similar analogy, more or less strongly marked, holds also in their internal organs[1037]; so that it may be safely affirmed, that if all the invertebrate insects, though gifted with numerous peculiarities, present the most striking picture of those animals that have an internal skeleton, and more particularly of the _Mammalia_,--we may assume it as a probability, the above circumstances being allowed their due weight, that where facts do not prove the contrary, the function of analogous organs is more or less synonymous, though perhaps the structure and _modus operandi_ may be different.

In the letter lately referred to, I observed that the antennæ of insects are analogous to _ears_ in Vertebrates[1038]. Their _number_ corresponds; they also stand out from the head; and what has weighed most with me, unless they are allowed as such, no other organ can have any pretension to be considered as representing the ear. If we reflect, that in every other part and organ, the head of insects has an analogy to that of _Mammalia_, we must regard it as improbable that these prominent organs should not also have their representative. Admitting then that they are the analogues of ears, it will follow, not as demonstratively certain, but as probable, that their _primary_ function may be something related to hearing. I do not say direct _hearing_, or that the vibrations of sound are communicated to the sensorium by a complex structure analogous to that of the internal ear in _Mammalia_--but something _related_ to hearing. I conceive that antennæ, by a peculiar structure, may collect notices from the atmosphere, receive pulses or vibrations, and communicate them to the sensorium, which, though not precisely to be called hearing, may answer the same purpose. From the _compound_ eyes that most of them have, the sense of seeing in insects must be very different from what it is in vertebrate animals; and yet we do not hesitate to call it _sight_: but since antennæ, as we shall see, apparently convey a _mixed_ sensation, I shall have no objection, admitting it as their primary function, to call it after Lehmann _Aëroscepsy_[1039]. I lately related some instances of _sound_ producing an effect on the _antennæ_ of insects: I will now mention another that I observed, still more remarkable. A little moth was reposing upon my window; I made a quiet, not loud, but distinct noise: the antenna nearest to me immediately moved towards me. I repeated the noise at least a dozen times, and it was followed every time by the same motion of that organ; till at length the insect being alarmed became more agitated and violent in its motions. In this instance it could not be _touch_; since the antenna was not applied to a surface, but directed towards the quarter from which the sound came, as if to listen. Bonsdorf made similar observations, to which Lehmann seems not disposed to allow their proper weight[1040]. It has been used as an argument to prove that antennæ are primarily _tactors_, or instruments of _touch_, that _Fœnus Jaculator_, before it inserts its ovipositor, plunges its _antennæ_ into the hole forming the nidus of the bee, to the grub of which it commits its egg[1041]. But had those who used this argument _measured_ the antennæ and the ovipositor of this ichneumon, they would have discovered that the latter is thrice the length of the former: and as these insects generally insert it so that even part of the abdomen enters the hole, it is clear that the antenna cannot _touch_ the larva; its object therefore cannot be to explore by that sense. Others suppose that by these organs it _scents_ out the destined nidus for its eggs; but Lehmann has satisfactorily proved that they are not _olfactory_ organs. We can therefore only suppose, either that by means of its antennæ it _hears_ a slight noise produced by the latent grub, perhaps by the action of its mandibles; or else that by its motions it generates a _motion_ in the atmosphere of its habitation, which striking upon the antennæ of the _Fœnus_, are by them communicated to its sensory. A similar disproportion is observable between the antennæ and ovipositor of _Pimpla Manifestator_, before signalized[1042]. Bees, when collecting honey and pollen, first insert the organs in question into the flowers which they visit; but, as I have more than once observed, they merely insert the _tip_ of them. If anthers are bursting, or the nectar is exuding, these processes probably are attended by a slight noise, or motion of the air within the blossom, which, as in the last case, affects, without immediate contact, the exploring organs.

If the _structure_ of antennæ be taken into consideration, it will furnish us with additional reasons in favour of the above hypothesis, with regard to their primary function. We shall find that these organs, in most of those insects which take their food by suction, are usually less gifted with powers of motion, than they are in the mandibulate tribes; so that in the majority of the Homopterous _Hemiptera_ and _Diptera_, as is generally acknowledged, they cannot be used for _touch_. Under this view, they may be divided into _active_ antennæ and _passive_ antennæ: of the former, the _most_

## active and versatile are those of the _Hymenoptera_. By means of