the little animals suck up their repast; thus, pump, which, more effective than ours, from which it draws the fluid". A third description of insects, those FOOD OF INSECTS. the extremity, and others serales wo, even to the very handles, was-atten The blood-thirsty gat as fre, some ons in these organs which era, and in many of the as instru ptera, comprising the whole tribe of instruments is ext ca) there is bu Others (Empi needle-shape/ gether forr seen an and I b and C man and even ماني proportion uty of food con a detail of which he Colonel Machell on the caja, he ascertained that, though nirty-six grains voided every twelve een to eighteen grains weight of excre.id not increase in weight in the same period han one or two grains. On the other hand, many Carnivorous larvæ increase in weight in full proportion to the food consumed, and that in an astonishing degree. Redi found that the maggots of flesh-flies, of which one day, twenty-five or thirty did not weigh above a grain, the next weighed seven grains each; having thus in * Obs. on the Animal Economy, p. 221. Compare Reaum. ii. 167. urs become about two hundred times the faculty of sustaining a long absof food. This seems to depend abits. If the insect feeds on f which there is not much it commonly requires ary, it is an insect of ing long deprived wer of fasting, "ous facts by FOOD OF INSECTS. wo, even to the very handles, buck-Assad jder, the scorpion have all in- e organs which gany of the anifest the Le. al exist with atly uninjured, for get it, it will devour Vaillant, whose autho assures us that he kept a spider a sealed glass for ten months, at the ume, though shrunk in size, it was as vi everb. And Mr. Baker, so well known for croscopical discoveries, states that he kept a beetle Blaps mortisaga) alive for three years without food of any kind. Some insects, not of a predaceous description, are gifted with a similar power of abstinence. Leeuwenhoek tells us that a mite, which he had gummed alive to the point of a needle and placed before his microscope, lived in that situation eleven weeks. In some cases the very want of food, however para a Redi de Insectis, 39. ↳ New Travels, i. xxxix. ← Phil. Trans. 1740, p. 441. I confess, notwithstanding Mr. Baker's general accuracy, that I suspect some mistake here. Leeuw. Op. ii. 363. While in the state of larvæ the quantity of food consumed by insects is vastly greater in proportion to their bulk than that required by larger animals. Many caterpillars eat daily twice their weight of leaves, which is as if an ox, weighing sixty stone, were to devour every twentyfour hours three quarters of a ton of grass-a power of stomach which our graziers may thank their stars that their oxen are not endowed with. A probable proximate cause for this voracity in the case of herbivorous larvæ has been assigned by John Hunter, who attributes it to the circumstance of their stomach not having the power of dissolving the vegetable matters received into it, but merely of extracting from them a juice. This is proved both by their excrement, which consists of coiledup and hardened particles of leaf, that being put into water expand like tea; and by the great proportion which the excrement bears to the quantity of food consumed. From experiments, with a detail of which he has favoured me, made by Colonel Machell on the caterpillars of Bombyx Caja, he ascertained that, though a larva weighing thirty-six grains voided every twelve hours from fifteen to eighteen grains weight of excrement, it did not increase in weight in the same period more than one or two grains. On the other hand, many carnivorous larvæ increase in weight in full proportion to the food consumed, and that in an astonishing degree. Redi found that the maggots of flesh-flies, of which one day, twenty-five or thirty did not weigh above a grain, the next weighed seven grains each; having thus in Obs. on the Animal Economy, p. 221. Compare Reaum. ii. 167. twenty-four hours become about two hundred times heavier than before". Some insects have the faculty of sustaining a long abs This seems to depend tinence from all kinds of food. upon the nature of their habits. a substance of a deficiency of which there is not much probability, as on vegetables, &c. it commonly requires a frequent supply. If, on the contrary, it is an insect of prey, and exposed to the danger of being long deprived of its food, it is often endowed with a power of fasting, which would be incredible but for the numerous facts by which it is authenticated. The ant-lion will exist without the smallest supply of food, apparently uninjured, for six months; though, when it can get it, it will devour daily an insect of its own size. Vaillant, whose authority may be here taken, assures us that he kept a spider without food under a sealed glass for ten months, at the end of which time, though shrunk in size, it was as vigorous as ever. And Mr. Baker, so well known for his microscopical discoveries, states that he kept a beetle (Blaps mortisaga) alive for three years without food of any kind. Some insects, not of a predaceous description, are gifted with a similar power of abstinence. Leeuwenhoek tells us that a mite, which he had gummed alive to the point of a needle and placed before his microscope, lived in that situation eleven weeks. In some cases the very want of food, however para * Redi de Insectis, 39. b New Travels, i. xxxix. © Phil. Trans. 1740, p. 441. I confess, notwithstanding Mr. Baker's general accuracy, that I suspect some mistake here. Leeuw. Op. ii. 363. doxical the proposition, seems actually to be a mean of prolonging the life of insects. At least one such instance has fallen under my own observation. The aphidivorous flies, such as Syrphus Pyrastri, &c. live in the larva state ten or twelve days, in the pupa state about a fortnight, and as perfect insects sometimes possibly as long-the whole term of their existence in summer not exceeding at the very utmost six weeks. But one, which I put under a glass on the 2d of June, 1811, when about half grown, and, after supplying it with Aphides once or twice, by accident forgot, I found to my great astonishment alive three months after; and it actually lived until the June following without a particle of food. It had therefore existed in the larva state more than eight times as long as it would have lived in all its states, if it had regularly undergone its metamorphoses-which is as extraordinary a prolongation of life as if a man were to live 560 years. It is true that its existence was not worth having even to the larva of a fly. For the last eight months it remained without motion, attached by its pos terior pair of tubercles to the paper on which it was placed, manifesting no other symptoms of life than by moving the a Not having ever met with another specimen, I am unable to say of what precise species of aphidivorous fly it is the larva, nor can I find a figure of it, though it approaches near to one given by De Geer (vi. t. 7. f. 1-3). Its shape is oblong-oval, length about four lines, and colour pale red speckled with black. Each of the seven or eight segments which compose the body projects on each side into three serrated flat aculei or teeth; three or four similar but smaller aculei arm the head: and two, much larger than the rest, the anus, one on each side of the usual bifid protuberance which bears the respiratory plates. A bifid tubercular elevation is also placed in the middle of the back of each segment. |