140 INSECT TRANSFORMATIONS. 



low, or green colour, and apparently analogous to fat 

 in the larger animals.* This furnishes, as is further 

 supposed, a store of nutriment for promoting the growth 

 of the butterfly. t 



This brief sketch will serve to give the reader a tole- 

 rable notion of the internal structure of caterpillars, and 

 the manner in which their food is elaborated into nutri- 

 ment; but when we know that Ljonnet wrote a large 

 quarto volume on the structure of a single caterpillar, 

 and that INIalpighi, Heroldt, Ramdohr, Sprengel, and 

 Marcel de Serres, are little less voluminous, it will be 

 understood that we give it merely as a sketch which 

 we could easily have extended, had it appeared, as it 

 does UMt, to be suitable to our plan. It will prove more 

 interesting, we think, to pass now to the external struc- 

 ture and appearance. 



It will be obvious from what we have said respect- 

 ing the colours of eggs, that we are not inclined to 

 adopt in all its extent the theory of many naturalists, 

 which maintains the peculiar colours and f()rms of ani- 

 mals to be given them by nature for the purpose of 

 concealment 1mm their enemies. As in the instance 

 of caterpillars this theory meets us agam in full force, 

 we shall mention a tew facts which appear not only to 

 be at variance with it, but show, we think, tiiat the 

 facts- of the theorists may stand as appropriately for 

 exceptions as for a general rule. Since caterpillars 

 form the staple food of soil-billed birds and of the 

 young of most hard-billed birds, not to mention the 

 parasite grubs of ichneumon-Hies which destroy great 

 numbers, nature has provided an immense abundance 

 of them, beyond what is requisite for continuing the 

 race. Were it maintained, therefore, that tlioy were 

 all by design so formed and coloured as to deceive the 

 eyes of birds and ichneumons, the purpose of their 



* Lyonnet, Anal, de la Chenille, 106. 

 1 Ri-aumur, Mem. i, 145. 



