We are indebted to De Geer for the history of a field-bug (Pentatoma grisea), a species found in this country, which shows marks of affection for her young such as I trust will lead you, notwithstanding any repugnant association that the name may call up, to search upon the birch tree, which it inhabits, for so interesting an insect. The family of this field-bug consists of thirty or forty young ones, which she conducts as a hen does her chickens. She never leaves them; and as soon as she begins to move, all the little ones closely follow, and whenever she stops assemble in a cluster round her. De Geer having had occasion to cut a branch of birch peopled with one of those families, the mother showed every symptom of excessive uneasiness. In other circumstances such an alarm would have caused her immediate flight; but now she never stirred from her young, but kept beating her wings incessantly with a very rapid motion, evidently for the purpose of protecting them from the apprehended danger[681].—As far as our knowledge of the economy of this tribe of insects extends, there is no other species that manifests a similar attachment to its progeny; but such may probably be discovered by future observers.
It is De Geer also that we have to thank for a series of interesting observations on the maternal affection exhibited by the common earwig. This curious insect so unjustly traduced by a vulgar prejudice,—as if the Creator had willed that the insect world should combine within itself examples of all that is most remarkable in every other department of nature,—still more nearly approaches the habits of the hen in her care of her family. She absolutely sits upon her eggs as if to hatch them—a fact which Frisch appears first to have noticed—and guards them with the greatest care. De Geer, having found an earwig thus occupied, removed her into a box where was some earth, and scattered the eggs in all directions. She soon, however, collected them one by one with her jaws into a heap, and assiduously sat upon them as before. The young ones, which resemble the parent except in wanting elytra and wings, and, strange to say, are as soon as born larger than the eggs which contained them, immediately upon being hatched creep like a brood of chickens under the belly of the mother, who very quietly suffers them to push between her feet, and will often, as De Geer found, sit over them in this posture for some hours[682]. This remarkable fact I have myself witnessed, having found an earwig under a stone which I accidentally turned over, sitting upon a cluster of young ones just as this celebrated naturalist has described.
We are so accustomed to associate the ideas of cruelty and ferocity with the name of spider, that to attribute parental affection to any of the tribe seems at first view almost preposterous. Who indeed could suspect that animals which greedily devour their own species whenever they have opportunity, should be susceptible of the finer feelings? Yet such is the fact. There is a spider common under clods of earth (Lycosa saccata) which may at once be distinguished by a white globular silken bag about the size of a pea, in which she has deposited her eggs, attached to the extremity of her body. Never miser clung to his treasure with more tenacious solicitude than this spider to her bag. Though apparently a considerable incumbrance, she carries it with her every where. If you deprive her of it, she makes the most strenuous efforts for its recovery; and no personal danger can force her to quit the precious load. Are her efforts ineffectual? A stupefying melancholy seems to seize her, and when deprived of this first object of her cares, existence itself appears to have lost its charms. If she succeeds in regaining her bag, or you restore it to her, her actions demonstrate the excess of her joy. She eagerly seizes it, and with the utmost agility runs off with it to a place of security. Bonnet put this wonderful attachment to an affecting and decisive test. He threw a spider with her bag into the cavern of a large ant-lion, a ferocious insect which conceals itself at the bottom of a conical hole constructed in the sand for the purpose of catching any unfortunate victim that may chance to fall in. The spider endeavoured to run away, but was not sufficiently active to prevent the ant-lion from seizing her bag of eggs, which it attempted to pull under the sand. She made the most violent efforts to defeat the aim of her invisible foe, and on her part struggled with all her might. The gluten, however, which fastened her bag, at length gave way, and it separated: but the spider instantly regained it with her jaws, and redoubled her efforts to rescue the prize from her opponent. It was in vain: the ant-lion was the stronger of the two, and in spite of all her struggles dragged the object of contestation under the sand. The unfortunate mother might have preserved her own life from the enemy: she had but to relinquish the bag, and escape out of the pit. But, wonderful example of maternal affection! she preferred allowing herself to be buried alive along with the treasure dearer to her than her existence; and it was only by force that Bonnet at length withdrew her from the unequal conflict. But the bag of eggs remained with the assassin: and though he pushed her repeatedly with a twig of wood, she still persisted in continuing on the spot. Life seemed to have become a burthen to her, and all her pleasures to have been buried in the grave which contained the germe of her progeny[683]! The attachment of this affectionate mother is not confined to her eggs. After the young spiders are hatched, they make their way out of the bag by an orifice, which she is careful to open for them, and without which they could never escape[684]; and then, like the young of the Surinam toad (Rana pipa), they attach themselves in clusters upon her back, belly, head, and even legs; and in this situation, where they present a very singular appearance, she carries them about with her and feeds them until their first moult, when they are big enough to provide their own subsistence. I have more than once been gratified by a sight of this interesting spectacle; and when I nearly touched the mother, thus covered by hundreds of her progeny, it was most amusing to see them all leap from her back and run away in every direction.
A similar attachment to their eggs and young is manifested by many other species of the same tribe, particularly of the genera Lycosa and Dolomeda. Clubiona holosericea was found by De Geer in her nest with fifty or sixty young ones, when manifesting nothing of her usual timidity, so obstinately did she persist in remaining with them, that to drive her away it was necessary to cut her whole nest in pieces[685].
I must now conduct you to a hasty survey of those insects which live together in societies and fabricate dwellings for the community, such as ants, wasps, bees, humble-bees, and termites, whose great object (sometimes combined indeed with the storing up of a stock of winter provisions for themselves) is the nutrition and education of their young. Of the proceedings of many of these insects we know comparatively nothing. There are, it is likely, some hundreds of distinct species of bees which live in societies, and form nests of a different and peculiar construction. The constitution of these societies is probably as various as the exterior forms of their nests, and their habits possibly curious in the highest degree; yet our knowledge is almost confined to the economy of the hive-bee and of some species of humble-bees. The same may be said of wasps, ants, and termites, of which, though there is a vast variety of different kinds, we are acquainted with the history of but a very few. You will not therefore expect more than a sketch of the most interesting traits of affection for their young, manifested by the common species of each genus.
One circumstance must be premised with regard to the education of the young of most of those insects which live in society, truly extraordinary, and without parallel in any other department of nature: namely, that this office, except under particular circumstances, is not undertaken by the female which has given birth to them, but by the workers, or neuters as they are sometimes called, which, though bound to the offspring of the common mother of the society by no other than fraternal ties, exhibit towards them all the marks of the most ardent parental affection, building habitations for their use, feeding them and tending them with incessant solicitude, and willingly sacrificing their lives in defence of the precious charge. Thus sterility itself is made an instrument of the preservation and multiplication of species; and females too fruitful to educate all their young, are indulged by Providence with a privilege without which nine tenths of their progeny must perish.
The most determined despiser of insects and their concerns—he who never deigned to open his eyes to any other part of their economy—must yet have observed, even in spite of himself, the remarkable attachment which the inhabitants of a disturbed nest of ants manifest towards certain small white oblong bodies with which it is usually stored. He must have perceived that the ants are much less intently occupied with providing for their own safety, than in carrying off these little bodies to a place of security. To effect this purpose the whole community is in motion, and no danger can divert them from attempting its accomplishment. An observer having cut an ant in two, the poor mutilated animal did not relax in its affectionate exertions. With that half of the body to which the head remained attached, it contrived previously to expiring to carry off ten of these white masses into the interior of the nest! You will readily divine that these attractive objects are the young of the ants in one of the first or imperfect states. They are in fact not the eggs, as they are vulgarly called, but the pupæ, which the working ants tend with the most patient assiduity. But I must give you a more detailed account of their operations, beginning with the actual eggs.
These, which are so small as to be scarcely visible to the naked eye, as soon as deposited by the queen ant, who drops them at random in her progress through the nest, are taken charge of by the workers, who immediately seize them and carry them in their mouths, in small parcels, incessantly turning them backwards and forwards with their tongue for the purpose of moistening them, without which they would come to nothing. They then lay them in heaps, which they place in separate apartments[686], and constantly tend until hatched into larvæ; frequently in the course of the day removing them from one quarter of the nest to another, as they require a warmer or cooler, a moister or drier atmosphere; and at intervals brooding over them as if to impart a genial warmth[687]. Experiments have been made to ascertain whether these assiduous nurses could distinguish their eggs if intermixed with particles of salt and sugar, which to an ordinary observer they very much resemble; but the result was constantly in favour of the sagacity of the ants. They invariably selected the eggs from whatever materials they were mixed with, and re-arranged them as before[688].
New and more severe labours succeed the birth of the young grubs which are disclosed from the eggs after a few days. The working ants are now almost without remission engaged in supplying their wants and forwarding their growth. Every evening an hour before sunset they regularly remove the whole brood, as well as the eggs and pupæ, which in an old nest all require attention at the same time, to cells situated lower down in the earth, where they will be safe from the cold; and in the morning they as constantly remove them again towards the surface of the nest. If, however, there is a prospect of cold or wet weather, the provident ants forbear on that day transporting their young from the inner cells, aware that their tender frames are unable to withstand an inclement sky. What is particularly worthy of notice in this herculean task, the ants constantly regulate their proceedings by the sun, removing their young according to the earlier or later rising and setting of that luminary. As soon as his first rays begin to shine on the exterior of the nest, the ants that are at the top go below in great haste to rouse their companions, whom they strike with their antennæ, or, when they do not seem to comprehend them, drag with their jaws to the summit till a swarm of busy labourers fill every passage. These take up the larvæ and pupæ, which they hastily transport to the upper part of their habitation, where they leave them a quarter of an hour, and then carry them into apartments where they are sheltered from the sun's direct rays[689].