398 FOOD OF INSECTS. 



terpillars of Euprepia Caja, he ascertained that, though 

 a larva weighing thirty-six grains voided every twelve 

 hours from fifteen to eighteen grains weight of excre- 

 ment, 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 1 . 



Some insects have the faculty of sustaining a long abs- 

 tinence 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 with- 

 out 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 autho- 

 rity 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 vi- 

 gorous as ever b . And Mr. Baker, so well known for his 

 microscopical discoveries, states that he kept a darkling 

 beetle (Blaps mortisagd) alive for three years without 



a Redi dc Insectis, 39. b New Travels, i. xxxix. 



