FOOD OF INSECTS. 259 



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 twenty-four 

 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 larvae 

 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 coiled-up 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 con- 

 sumed. From experiments, with a detail of which he has favored me, 

 made by Colonel Machell of Beverly on the caterpillars of Etiprepia 

 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 larvae 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 twenty-four hours become about two hundred times heavier 

 than before.^ 



Some insects have the faculty of sustaining a long abstinence from all 

 kinds of food. This seems to depend upon the nature of their habits. 

 If the insect feeds on 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 darkling 

 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'^; and Mr. Stephens, having, in June, 

 1831, put a specimen of Lepisma saccharina (the common "wood" or 

 " sugar fish") in a pill-box containing only a few grains of magnesia, found 

 it, to his great surprise, alive and active in June, 1833, after this pro- 

 tracted confinement, without food, of two years.^ 



' Obs. on the Animal (Economy, p. 221. Compare Reaum. ii. 167. 



* Redi de Insectis, 39. s jy^^ 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. « EnUm. Mag. i. 526. 



