FOOD OF INSECTS. 397 



moth which proceeds from the silk-worm, and several 

 others of the same order; the different species of gad-flies, 

 and the Ephemerae, insects whose history is so well known 

 as to afford a moral or a simile to those most ignorant of 

 natural history. AIL these live so short a time in the 

 perfect state as to need no food. Indeed it may be laid 

 down as a general rule, that almost all insects in this 

 state eat much less than 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 a drop or two of 

 any sweet liquid. 



While in the state of larva? the quantity of food con- 

 sumed by insects is vastly greater in proportion to their 

 bulk than that required by larger animals. Many cater- 

 pillars eat daily twice their weight of leav(;;s, 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 proxi- 

 mate 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 favoured me, made by Colonel Machell on the ca- 



Obs. on the Animal CEcononiy, p. 221. Compare Reaum. ii. 167. 



