CRYPTIC COLOUE. 



and colouring' may render a large insect indistinguishable from its 



surroundings. Leaf insects are coloured like a leaf, which may be 



green or dry. Many moths (fig. 61) sit with expanded wings and the 



colour scheme blends with the bark 



on which they sit so well that the 



moth escapes notice. Others sit 



with folded wings and exactly 



resemble bark ; their lower wings 



are then hidden and may be brightly 



coloured. Grasshoppers commonly 



have cryptic colouring, some being 



dry-grass colour, others green-grass 



colour, and so on. Grasshoppers 



that live in the fields and sit on 



the ground are earth colour (fig. 62) 



and have roughened backs like 



a lump of soil. 



Cryptic colouring is very com- 

 mon, usually combined with cryptic 

 form ; it may occur in two different 

 colour schemes in the life of an 

 insect, the change occurring when 

 the changed surroundings make it 



necessary. Thus a young grasshopper that lives in green gi'ass is green, 

 but becomes dry-grass colour when the grass ripens and the insect 

 becomes full grown. A caterpillar that sits on a leafy tree is green, per- 

 haps so long as it remains there ; when it has to crawl down the trunk 

 to reach the ground and pupate, it becomes brown, as the green would 

 make it conspicuous against the bark of the tree. Those larvae which live 

 in nests or other hidden spots change but little at each moult unless their 

 habits require a change. The changes may be small and imperceptible 

 or very marked, and bear a close relation to the differing habits of the 

 young and the old insect. The same is true of the nymphs of the 

 Orthoptera and Hemiptera. With every moult there are distinct changes 

 not due alone to the gradual development of the wings and other 

 imaginal characters, but to changes of colour and form necessitated by 

 changing environment. The very young nymphs of a grasshopper, for 

 instance, which live concealed in grass require a very different colouring 

 from the half -grown insect which leaps actively about in the open ; the 

 colour therefore changes at each moult, adapting the insect to its 

 increased activities and gradually giving place to the colour scheme of 



FIG. 62. 

 Surface Grasshopper, 



