We often wonder how the cheese-mite (Acarus Siro) is at hand to attack a cheese wherever deposited; but when we learn from Leeuwenhoek, that one lived eleven weeks gummed on its back to the point of a needle without food, our wonder will be diminished[314]. Another species of mite (Uropoda vegetans) was observed by De Geer to live some time in spirits of wine[315]. This last circumstance reminds me of an event which befel myself, that I cannot refrain from relating to you, since it was the cause of my taking up the pursuit I am recommending to you. One morning I observed on my study window a little lady-bird yellow with black dots (Coccinella 22-punctata)—"You are very pretty," said I to myself, "and I should like to have a collection of such creatures." Immediately I seized my prey, and not knowing how to destroy it, I immersed it in geneva. After leaving it in this situation a day and a night, and seeing it without motion, I concluded it was dead, and laid it in the sun to dry. It no sooner, however, felt the warmth than it began to move, and afterward flew away. From this time I began to attend to insects.—The chamæleon-fly (Stratyomis Chamæleon) was observed by Swammerdam to retain its vital powers after an immersion equally long in spirits of wine. Gœdart affirms that this fly, on which account it was called chamæleon, will live nine months without food; a circumstance, if true, more wonderful than what I formerly related to you with respect to one of the aphidivorous flies[316].—If insects will escape unhurt from a bath of alcohol, it may be supposed that one of water will be less to be dreaded by them. To this they are often exposed in rainy weather, when ruts and hollows are filled with water: but when the water is dried up, it is seldom that any dead carcases of insects are to be seen in them. Mr. Curtis submerged the fragile aphides for sixteen hours; when taken out of the water they immediately showed signs of life, and out of four, three survived the experiment:—an immersion of twenty-four hours, however, proved fatal to them[317].
The late ingenious, learned, and lamented Dr. Reeve of Norwich once related to me that he found in a hot fountain on the top of a mountain, near Leuk in the Valais in Switzerland, in which the thermometer stood at 205°, transparent larvæ, probably of gnats, or some such insect.—Lord Bute also, in a letter to my late revered friend, the Rev. William Jones of Nayland, imparts a similar observation made by His Lordship at the baths of Abano, near the Euganian mountains, on the borders of the Paduan states. They are strong, sulphureous, boiling springs, oozing out of a rocky eminence in great numbers, and spreading over an acre of the top of a gentle hill. In the midst of these boiling springs, within three feet of five or six of them, rises a tepid one about blood warm. But the most extraordinary circumstance which he relates is, that not only confervas were found in the boiling springs, but numbers of small black beetles, that died upon being taken out and plunged into cold water[318].—And once, having taken in the hot dung of my cucumber-bed a small beetle (Synchita Juglandis), I immersed it in boiling water; and after keeping it submerged a sufficient time, as I thought, to destroy it, upon taking it out, and laying it to dry, it soon began to move and walk. Its native station being of so high a temperature, Providence has fitted it for it, by giving it extraordinary powers of sustaining heat. Other insects are as remarkable for bearing any degree of cold. Some gnats that De Geer observed, survived after the water in which they were was frozen into a mass of ice: and Reaumur relates many similar instances[319].
The last passive means of defence that I mentioned, was the multiplication of insects. Some species, the Aphides for instance, and the Grasshoppers and Locusts, have such an infinite host of enemies, that were it not for their numbers the race would soon be annihilated.—But as passive means of defence have detained us sufficiently long, it is enough to have touched upon this head. Let us then now proceed to such as may be called active; in which the volition of the animal bears some part.
II. The active means of defence, which tend to secure insects from injury or attack, are much more numerous and diversified than the passive; and also more interesting, since they depend, more or less, upon the efforts and industry of these creatures themselves. When urged by danger, they endeavour to repel it either by having recourse to certain attitudes or motions; producing particular noises; emitting disagreeable scents or fluids; employing their limbs; or weapons, and valour; concealing themselves in various ways; or by counteracting the designs and attack of their enemies by contrivances that require ingenuity and skill.
The attitudes which insects assume for this purpose are various. Some are purely imitative, as in many instances detailed above. I possess a diminutive rove-beetle (Aleochara complicans, K. Ms.) to which my attention was attracted as a very minute, shining, round, black pebble. This successful imitation was produced by folding its head under its breast, and turning up its abdomen over its elytra; so that the most piercing and discriminating eye would never have discovered it to be an insect.—I have observed that a carrion beetle (Silpha thoracica) when alarmed has recourse to a similar manœuvre. Its orange-coloured thorax, the rest of the body being black, renders it particularly conspicuous. To obviate this inconvenience, it turns its head and tail inwards till they are parallel with the trunk and abdomen, and gives its thorax a vertical direction, when it resembles a rough stone.—The species of another genus of beetles (Agathidium) will also bend both head and thorax under the elytra, and so assume the appearance of shining globular pebbles.
Related to the defensive attitude of the two last-mentioned insects, and precisely the same with that of the Armadillo (Dasypus) amongst quadrupeds, is that of one of the species of woodlouse (Armadillo vulgaris). This insect when alarmed rolls itself up into a little ball. In this attitude its legs and the underside of the body, which are soft, are entirely covered and defended by the hard crust that forms the upper surface of the animal. These balls are perfectly spherical, black, and shining, and belted with narrow white bands, so as to resemble beautiful beads; and could they be preserved in this form and strung, would make very ornamental necklaces and bracelets. At least so thought Swammerdam's maid, who, finding a number of these insects thus rolled up in her master's garden, mistaking them for beads, employed herself in stringing them on a thread; when to her great surprise, the poor animals beginning to move and struggle for their liberty, crying out and running away in the utmost alarm she threw down her prize[320].—The golden-wasp tribe also, (Chrysis and Parnopes,) all of which I suspect to be parasitic insects, roll themselves up, as I have often observed, into a little ball when alarmed, and can thus secure themselves—the upper surface of the body being remarkably hard, and impenetrable to their weapons—from the stings of those Hymenoptera whose nests they enter with the view of depositing their eggs in their offspring. Latreille noticed this attitude in Parnopes carnea, which, he tells us, Bembex rostrata pursues, though it attacks no other similar insect, with great fury; and, seizing it with its feet, attempts to dispatch it with its sting, from which it thus secures itself[321].
Other insects endeavour to protect themselves from danger by simulating death. The common dung-chafer (Geotrupes stercorarius) when touched, or in fear, sets out its legs as stiff as if they were made of iron-wire—which is their posture when dead—and remaining perfectly motionless, thus deceives the rooks which prey upon them, and like the ant-lion before celebrated[322] will eat them only when alive. A different attitude is assumed by one of the tree-chafers (Hoplia pulverulenta) probably with the same view. It sometimes elevates its posterior legs into the air, so as to form a straight vertical line, at right angles with the upper surface of its body.—Another genus of insects of the same order, the pill-beetles (Byrrhus), have recourse to a method the reverse of this. They pack their legs, which are short and flat, so close to their body, and lie so entirely without motion when alarmed, that they look like a dead body, or rather the dung of some small animal.—Amongst the weevil tribe, most of the species of Germar's genus Cryptorynchus, including several modern genera or subgenera, when an entomological finger approaches them, as I have often experienced to my great disappointment, applying their rostrum and legs to the underside of their trunk, fall from the station on which you hope to entrap them, to the ground or amongst the grass; where, lying without stirring a limb, they are scarcely to be distinguished from the soil around them. Thus also, doubtless, they often disappoint the birds as well as the entomologist.—A little timber-boring beetle (Anobium pertinax), (and others of the genus have the same faculty,) which, when the head is withdrawn somewhat within the thorax, much resembles a monk with his hood, has long been famous for a most pertinacious simulation of death. All that has been related of the heroic constancy of American savages, when taken and tortured by their enemies, scarcely comes up to that which these little creatures exhibit. You may maim them, pull them limb from limb, roast them alive over a slow-fire[323], but you will not gain your end; not a joint will they move, nor show by the least symptom that they suffer pain. Do not think, however, that I ever tried these experiments upon them myself, or that I recommend you to do the same. I am content to believe the facts that I have here stated upon the concurrent testimony of respectable witnesses, without feeling any temptation to put the constancy of the poor insect again to the test.—A similar apathy is shown by some species of saw-flies (Serrifera), which when alarmed conceal their antennæ under their body, place their legs close to it, and remain without motion even when transfixed by a pin.—Spiders also simulate death by folding up their legs, falling from their station, and remaining motionless; and when in this situation, they may be pierced and torn to pieces without their exhibiting the slightest symptom of pain[324].
There is a certain tribe of caterpillars called surveyors (Geometræ), that will sometimes support themselves for whole hours, by means of their posterior legs, solely upon their anal extremity, forming an angle of various degrees with the branch on which they are standing, and looking like one of its twigs. Many concurring circumstances promote this deception. The body is kept stiff and immoveable with the separations of the segments scarcely visible; it terminates in a knob, the legs being applied close, so as to resemble the gem at the end of a twig; besides which, it often exhibits intermediate tubercles which increase the resemblance. Its colour too is usually obscure, and similar to that of the bark of a tree. So that, doubtless, the sparrows and other birds are frequently deceived by this manœuvre, and thus balked of their prey. Rösel's gardener, mistaking one of these caterpillars for a dead twig, started back in great alarm when upon attempting to break it off he found it was a living animal[325].
But insects do not always confine themselves to attitudes by which they meditate escape or concealment; they sometimes, to show their courage, put themselves in a posture of defence, and even have in view the annoyance as well as the repelling of their foes. The great rove-beetle (Goerius olens) presents an object sufficiently terrific, when with its large jaws expanded, and its abdomen turned over its head, like a scorpion, it menaces its enemies, some of which this ferocious attitude may deter from attacking it. Mr. Bingley informs us that the giant earwig (Labidura gigantea), a rare species that his researches have added to the catalogue of British insects, turns up over its head, in a similar manner, its abdomen, which being armed at the end with a large forceps must give it an appearance still more alarming[326].
The caterpillars of some hawk-moths (Sphinx), particularly that which feeds upon the privet, when they repose, holding strongly with their prolegs the branch on which they are standing, rear the anterior part of their body so as to form nearly a right angle with the posterior; and in this position it will remain perfectly tranquil,—thus eluding the notice of its enemies, or alarming them,—perhaps for hours. Reaumur relates that a gardener in the employment of the celebrated Jussieu used to be quite disconcerted by the self-sufficient air of these animals, saying they must be very proud, for he had never seen any other caterpillars hold their head so high[327]. From this attitude, which precisely resembles that which sculptors have assigned to the fabulous monster called by that name, the term Sphinx has been used to designate this genus of insects.—The caterpillar of a moth (Lophopteryx camelina) noticed by the author just quoted, whenever it rests from feeding, turns its head over its back, then become concave, at the same time elevating its tail, the extremity of which remains in a horizontal position, with two short horns like ears behind it. Thus the six anterior legs are in the air, and the whole animal looks like a quadruped in miniature; the tail being its head—the horns its ears—and the reflexed head simulating a tail curled over its back[328]. In this seemingly unnatural attitude it will remain without motion for a very long time.