100 ANIMAL COLORATION. 



ance, which would be considerably diminished did the middle 

 segments have legs. The anterior legs are often directed 

 forwards when the larva is resting outstretched from a branch, 

 and suggest buds at the extremity of a branchlet. The two pairs 

 of posterior legs, with which the larva grasps the branch, 

 in the Brimstone moth (Riimia crattegata), and the tract of 

 body lying between them has numerous minute fleshy tuber- 

 cles, which soften the contrast between the caterpillar and the 

 branch, and thus heighten its resemblance to a twig. These 

 Geometer caterpillars are very plentiful ; and any one can 

 observe them for himself even in a London garden. 



A resemblance to> a twig shown by a tree-feeding caterpillar 

 seems to be so obviously useful, that it might be assumed, 

 without any further discussion, that the need for protection 

 was the cause of the whole likeness which these caterpillars 

 bear to twigs. The Geometrfe form a large group of moths 

 spread over the whole world, and feeding in the larval con- 

 dition upon every variety of tree, shrub, and plant. They have, 

 therefore, to cope with most varied conditions, and with enemies 

 of all kinds. 



Although the prevailing device for protective purposes which 

 they exhibit is a likeness to a twig, there are some species, 

 which appear to imitate bits of curled-up and withered leaf, 

 or even empty snail-shells ; while others lose their resemblance 

 to a twig by their strikingly unt wig-like coloration (e.g. Magpie 

 moths), or by their habit of extending themselves along leaves- 

 instead of resting stretched out from a branch. And yet, in 

 spite of these varied resemblances, the same general form is 

 found in all Geometer larvre, and in no others excepting in 

 some genera which are nearly allied to these moths. 



We must, therefore, not too hastily assume that the chief 

 features of resemblance which the caterpillars of the Pepper- 



