224 FOOD OF INSECTS. 



in that of larvae. The voracious caterpillar, when transformed into a 

 butterfly, needs only a small quantity of honey ; and the gluttonous maggot, 

 when become a fly, contents itself with an occasional drop or two of any 

 sweet liquid. 



While in the state of larvae 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 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. l 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 propor- 

 tion 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 of Beverley on the caterpillars of Enprepia 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. 2 



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 fast- 

 ing, which would be incredible out 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. 3 And Mr. Baker, so well known for his micro- 

 scopical discoveries, states that he kept a darkling beetle (Blaps mortisaga) 

 alive for three years without food of any kind. 4 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 5 ; and Mr. Stephens, having, in June, 1831, put a specimen of 



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



2 Redi de Insectis, 39. 



5 New Travels, i. xxxix. 



4 Phil. Trans. 1740, p. 441. I confess, notwithstanding Mr. Baker's general accu- 

 racy, that I suspect some mistake here. 

 * Leeuw. Op. ii. 363. 



