PERFECT INSECT. 21 



plants themselves not showing further marks of 

 ravage, it is often thought that the mischief is over ; 

 ■whereas the trouhle may very likely have only ceased 

 for a while, to arise again when a new brood of insects 

 •comes, forth from the chrysalis or pupal state. 



Tig. 19. — Wheat-bulb I'ly, mag. ; larvffi and pupae, uat. size and mag. 



It is also to be observed that many of the brightly 

 coloured caterpillars, such as those of the Death's-head 

 Moth, alter in colour to a livid dirty tint when they 

 are about to cease feeding ; and thus the protection, 

 which is often given by similarity in general tone of 

 colouring of the grub to the colouring of its food, may 

 be changed to the protection of the more earth-like 

 tints when they are about to bury themselves. 



In the case of the Grasshoppers, Aphides, or other 

 insects, known as the " similarly changing," which 

 differ little in appearance and little in habits through- 

 ■out the three stages of their lives, the change is not 

 so marked. When the insect moults its old skin it 

 has to draw itself carefully out of its neatly fitting 

 <3oat, and the operation may be observed in detail if a 

 fair sized insect, such as a Grasshopper, is caught 

 just when it is about to moult. When I have watched 

 it myself the operation took twenty minutes. The 

 1:)ack of the insect, or rather of its old skin, cracked, 

 and through the opening there came out, very slowly 

 and carefully, the insect from within. Each portion 



