54 ON PLANTS AND INSECTS. [LECT. 



three points : What do the eye-spots and the faint 

 lateral line mean ? and why are some green, and some 

 brown, offering thus such a marked contrast to the leaves 

 of the Epilobium parvum, on which they feed ? Other 



FIG. 40. Chccrocampa elpenor. First stage. 



questions will suggest themselves later. I must now call 

 your attention to the fact that, when the caterpillars first 

 quit the egg, and come into the world (Fig. 40), they are 

 quite different in appearance, being, like so many other 



FIG. 41. Chccrocampa elpenor. Second stage. 



small caterpillars, bright green, and almost exactly the 

 colour of the leaves on which they feed. That this colour 

 is not a necessary or direct consequence of the food, we 

 see from the case of quadrupeds, which, as I need scarcely 



FIG. 42. Chcerocampa elpcno'r. Just before second moult. 



say, are never green. It is, however, so obviously a 

 protection to small caterpillars, that the explanation of 

 their green colour suggests itself to every one. After 

 five or six days, and when they are about a quarter of 



