It does not follow, however, that reason may not have a part in inducing some of these last-mentioned actions, though the actions themselves are purely instinctive. I do not pretend to explain in what way or degree they are combined; but certainly some of the facts do not seem to admit of explanation, except on this supposition. Thus, in the instance above cited from Huber, in which the bees bent a comb at right angles in order to avoid a slip of glass, the remarkable variations in the form of the cells can only, as I have there said, be referred to instinct. Yet the original determination to avoid the glass seems, as Huber himself observes, to indicate something more than instinct, since glass is not a substance against which Nature can be supposed to have forewarned bees, there being nothing in hollow trees (their natural abodes) resembling it either in polish or substance: and what was most striking in their operations was, that they did not wait until they had reached the surface of the glass before changing the direction of the comb, but adopted this variation at a considerable distance, as though they foresaw the inconveniences which might result from another mode of construction[804].—However difficult it may be to form a clear conception of this union of instinct and reason in the same operation, or to define precisely the limits of each, instances of these mixed actions are sufficiently common among animals to leave little doubt of the fact. It is instinct which leads a greyhound to pursue a hare; but it must be reason that directs "an old greyhound to trust the more fatiguing part of the chase to the younger, and to place himself so as to meet the hare in her doubles[805]."
As another instance of these mixed actions in which both reason and instinct seem concerned, but the former more decidedly, may be cited the account which Huber gives of the manner in which the bees of some of his neighbours protected themselves against the attacks of the death's-head-moth (Acherontia Atropos), laid before you in a former letter[806], by so closing the entrance of the hive with walls, arcades, casements, and bastions, built of a mixture of wax and propolis, that these insidious marauders could no longer intrude themselves.
We can scarcely attribute these elaborate fortifications to reason simply; for it appears that bees have recourse to a similar defensive expedient when attacked even by other bees; and the means employed seem too subtle and too well adapted to the end to be the result of this faculty in a bee.
But on the other hand, if it be most probable that in this instance instinct was chiefly concerned, if we impartially consider the facts, it seems impossible to deny that reason had some share in the operations. Pure instinct would have taught the bees to fortify themselves on the first attack. If the occupants of a hive had been taken unawares by these gigantic aggressors one night, on the second, at least, the entrance should have been barricadoed. But it appears clear from the statement of Huber, that it was not until the hives had been repeatedly attacked and robbed of nearly their whole stock of honey, that the bees betook themselves to the plan so successfully adopted for the security of their remaining treasures; so that reason taught by experience, seems to have called into action their dormant instinct[807].
If it be thus probable that reason has some influence upon the actions of insects, which must be mainly regarded as instinctive, the existence of this faculty is still more evident in numerous traits of their history where instinct is little if at all concerned. An insect is taught by its instincts the most unerring means to the attainment of certain ends; but these ends, as I have already had occasion more than once to remark, are limited in number, and such only as are called for by its wants in a state of nature. We cannot reasonably suppose insects to be gifted with instincts adapted for occasions that are never likely to happen. If therefore we find them, in these extraordinary and improbable emergencies, still availing themselves of the means apparently best calculated for ensuring their object;—and if in addition they seem in some cases to gain knowledge by experience; if they can communicate information to each other; and if they are endowed with memory;—it appears impossible to deny that they are possessed of reason.—I shall now produce facts in proof of each of these positions; not by any means all that might be adduced, but a few of the most striking that occur to me.
First, then, insects often in cases not likely to be provided for by instinct, adopt means evidently designed for effecting their object.
A certain degree of warmth is necessary to hatch a hen's eggs, and we give her little credit for reason in sitting upon them for this purpose. But if any one had ever seen a hen make her nest in a heap of fermenting dung, among the bark of a hot-bed, or in the vicinity of a baker's oven, where, the heat being as well adapted as the stoves of the Egyptians to bring her chickens into life, she left off the habit of her race, and saved herself the trouble of sitting upon them,—we should certainly pronounce her a reasoning hen: and if this hen had chanced to be that very one figured and so elaborately described by Professor Fischer, with the profile of an old woman[808], a Hindoo metaphysician at least could not doubt of her body, however hen-like, being in truth directed in its operations by the soul of some quondam amateur of poultry-breeding. Now societies of ants have more than once exhibited a deviation from their usual instinct, which to me seems quite as extraordinary and as indicative of reason as would be that supposed in a hen. A certain degree of warmth is required for the exclusion and rearing of their eggs, larvæ and pupæ; and in their ordinary abodes, as you have been already told[809], they undergo great daily labour in removing their charge to different parts of the nest, as its temperature is affected by the presence or absence of the sun. But Reaumur, in refuting the common notion of ants being injurious to bees, tells us that societies of the former often saved themselves all this trouble, by establishing their colonies between the exterior wooden shutters and panes of his glass hives, where, owing to the latter substance being a tolerably good conductor of heat, their progeny was at all times, and without any necessity of changing their situation, in a constant, equable, and sufficient temperature[810]. Bonnet observed the same fact. He found that a society of ants had piled up their young to the height of several inches, between the flannel-lined case of his glass hives and the glass. When disturbed they ran away with them, but always replaced them[811].
I am persuaded that after duly considering these facts, you will agree with me that it is impossible consistently to refer them to instinct, or to account for them without supposing some stray ant, that had insinuated herself into this tropical crevice, first to have been struck with the thought of what a prodigious saving of labour and anxiety would occur to her compatriots by establishing their society here;—that she had communicated her ideas to them;—and that they had resolved upon an emigration to this new-discovered country—this Madeira of ants—whose genial clime presented advantages which no other situation could offer. Neither instinct, nor any conceivable modification of instinct, could have taught the ants to avail themselves of a good fortune which but for the invention of glass hives would never have offered itself to a generation of these insects since the creation; for there is nothing analogous in nature to the constant and equable warmth of such a situation, the heat of any accidental mass of fermenting materials soon ceasing, and no heat being given out from a society of bees when lodged in a hollow tree, their natural residence. The conclusion, then, seems irresistible, that reason must have been their guide, inducing a departure from their natural instinct as extraordinary as would be that of a hen which should lay her eggs in a hot-bed, and cease to sit upon them.
The adaptation of means to an end not likely to have been provided for by instinct, is equally obvious in the ingenious mode by which a nest of humble-bees propped up their tottering comb, the particulars of which having before mentioned to you[812], I need not here repeat.