An Introduction to Entomology: Vol. 2 / or Elements of the Natural History of the Insects

by William Kirby; William Spence

ON THE INSTINCT OF INSECTS.

The greater part of those surprising facts connected with the manners and economy of insects, of which the relation has occupied the preceding letters, is to be referred, I have told you, to their instinct. But what, you will ask, is this instinct?—of what nature is this faculty which produces effects so extraordinary?

To this query I do not pretend to give any satisfactory answer. As I am quite of Bonnet's opinion, that philosophers will in vain torment themselves to define instinct, until they have spent some time in the head of an animal without actually being that animal—a species of metempsychosis through which I have never passed—I shall not attempt to explain what this mysterious energy is. It will not, however, I imagine, be very difficult to show what it is not; and some observations with this view, followed by an enumeration of peculiarities which distinguish the instincts of insects from those of other tribes of animals, and a short inquiry whether their actions are guided solely by instinct, will form the substance of this letter.

I. It is quite superfluous at this day to controvert the explanations of instinct advanced by some of the philosophers of the old school, such as that of Cudworth, who referred this faculty to a certain plastic nature; or that of Des Cartes, who contended that animals are mere machines. Nor, I fancy, would you thank me for entering into an elaborate refutation of the doctrine of Mylius, that many of the actions deemed instinctive are the effect of painful corporeal feelings; the cocoon of a caterpillar, for instance, being the result of a fit of the colic, produced by a superabundance of the gum which fills its silk-bags, and which exuding, is twisted round it, by its uneasy contortions, into a regular ball. Still less need I advert to the notable discovery of some pupils of Professor Winckler, that the brain, alias the soul, of a bee or spider, is impressed at the birth of the insect with certain geometrical figures, according to which models its works are constructed,—a position which these gentlemen demonstrate very satisfactorily by a memorable experiment in which they themselves were able to hear triangles.

It is as unnecessary to waste any words in refutation of the nonsense (for it deserves no better name) of Buffon, who refers the instinct of societies of insects to the circumstance of a great number of individuals being brought into existence at the same time, all acting with equal force, and obliged by the similarity of their internal and external structure, and the conformity of their movements, to perform each the same actions, in the same place, in the most convenient mode for themselves, and least inconvenient for their companions; whence results a regular, well-proportioned, and symmetrical structure: and he gravely tells us that the boasted hexagonal cells of bees are produced by the reciprocal pressure of the cylindrical bodies of these insects against each other[760]!!

Nor is it requisite to advert at length to the explanations of instinctive actions more recently given by Steffens, a German author (one of the transcendentalists, I conclude, from the incomprehensibility of his book to my ordinary intellect), who says that the products of the vaunted instinct of insects are nothing but "shootings out of inorganic animal masses" (anorgische anschüsse)[761]; and by Lamarck[762], who attributes them to certain inherent inclinations arising from habits impressed upon the organs of the animals concerned in producing them, by the constant efflux towards these organs of the nervous fluid, which during a series of ages has been displaced in their endeavours to perform certain actions which their necessities have given birth to. The mere statement of an hypothesis of which the enunciation is nearly unintelligible, and built upon the assumption of the presence of an unseen fluid, and of the existence of the animal some millions of years, is quite sufficient, and would even be unnecessary if it were not of such late origin. Neither shall I detain you with any formal consideration of the hypothesis advanced by Addison and some other authors, that instinct is an immediate and constant impulse of the Deity; which, to omit other obvious objections, is sufficiently refuted by the fact, that animals in their instincts are sometimes at fault, and commit mistakes, which on the above supposition could not in any case happen.

The only doctrine on the subject of instinct requiring any thing like a formal refutation, is that which, contending for the identity of this faculty with reason in man, maintains that all the actions of animals, however complicated, are, like those of the human race, the result of observation, invention, and experience. This theory, maintained by the sceptics, Pythagoras, Plato, and some other ancient philosophers, and in modern times by Helvetius, Condillac, and Smellie, has been by none more ingeniously supported than by Dr. Darwin, who in the chapter treating on instinct, in the first volume of his Zoonomia, has brought forward a collection of facts which give it a great air of plausibility. This plausibility, however, is merely superficial; and the result of a rigorous examination by any competent judge is, that the greater part of Dr. Darwin's facts bear more strongly in favour of the dissimilarity of instinct and reason than of their identity: and that those few which seem to support the latter position, are built upon the relations of persons ignorant of natural history, who have confused together distinct species of animals. Thus, because some anonymous informant told him that hive-bees when transported to Barbadoes, where there is no winter, ceased to lay up a store of honey, Dr. Darwin infers that all the operations of these insects are guided by reason and the adaptation of means to an end—a very just inference, if the statement from which it is drawn were accurate; but that it is not so, is known to every naturalist acquainted with the fact that many different species of bees store up honey in the hottest climates; and that there is no authentic instance on record of the hive-bees' altering in any age or climate their peculiar operations, which are now in the coldest and in the hottest regions precisely what they were in Greece in the time of Aristotle, and in Italy in the days of Virgil. Indeed the single fact, depending on the assertions of such accurate observers as Reaumur and Swammerdam, that a bee as soon after it is disclosed from the pupa as its body is dried and its wings expanded, and before it is possible that it should have received any instruction, betakes itself to the collecting of honey or the fabrication of a cell, which operations it performs as adroitly as the most hoary inhabitant of the hive, is alone sufficient to set aside all the hear-say statements of Dr. Darwin, and should have led him, as it must every logical reasoner, to the conclusion, that these and similar actions of animals cannot be referred to any reasoning process, nor be deemed the result of observation and experience.—It is true, it does not follow that animals, besides instinct, have not, in a degree, the faculty of reason also; and as I shall in the sequel endeavour to show, many of the actions of insects can be adequately explained on no other supposition. But to deny, as Dr. Darwin does, that the art with which the caterpillar weaves its cocoon, or the unerring care with which the moth places her eggs upon food that she herself can never use, are the effects of instinct, is as unphilosophical and contrary to fact, as to insist that the eagerness with which, though it has never tasted milk, the infant seeks for its mother's breast, is the effect of reason.

Instinct, then, is not the result of a plastic nature; of a system of machinery; of diseased bodily action; of models impressed on the brain; nor of organic shootings-out:—it is not the effect of the habitual determination for ages of the nervous fluid to certain organs; nor is it either the impulse of the Deity, or reason. Without pretending to give a logical definition of it, which while we are ignorant of the essence of reason is impossible, we may call the instincts of animals those unknown faculties implanted in their constitution by the Creator, by which, independent of instruction, observation, or experience, and without a knowledge of the end in view, they are impelled to the performance of certain actions tending to the well-being of the individual and the preservation of the species: and with this description, which is in fact merely a confession of ignorance, we must, in the present state of metaphysical science, content ourselves.

I here say nothing of that supposed connexion of the instinct of animals with their sensations, which has been introduced into many definitions of this mysterious power, for two reasons. In the first place, this definition merely sets the world upon the tortoise; for what do we know more than before about the nature of instinct, when we have called it, with Brown, a predisposition to certain actions when certain sensations exist, or with Tucker have ascribed it to the operation of the senses, or to that internal feeling called appetite? But, secondly, this connexion of instinct with bodily sensation, though probable enough in some instances, is by no means generally evident. We may explain in this way the instincts connected with hunger and the sexual passion, and some other particular facts, as the laying of the eggs of the flesh-fly in the flowers of Stapelia hirsuta, instead of in carrion their proper nidus, and of those of the common house-fly in snuff[763] instead of dung; for in these instances the smell seems so clearly the guide, that it even leads into error. But what connexion between sensation and instinct do we see in the conduct of the working-bees, which fabricate some of the cells in a comb larger than others, expressly to contain the eggs and future grubs of drones, though these eggs are not laid by themselves, and are still in the ovaries of the queen? So we may plausibly enough conjecture that the fury with which, in ordinary circumstances, at a certain period of the year, the working-bees are inspired towards the drones, is the effect of some disagreeable smell or emanation proceeding from them at that particular time: but how can we explain, on similar grounds, the fact that in a hive deprived of a queen, no massacre of the drones takes place? Lastly, to omit here a hundred other instances, as many of them will be subsequently adverted to, if we may with some show of reason suppose that it is the sensation of heat which causes bees to swarm; yet what possible conception can we form of its being bodily sensations that lead bees to send out scouts in search of a hive suitable for the new colony, several days before swarming?