INFANCY OF CRABS AND CATERPILLARS 249 



may be seen in our illustrations, the body bears an extra- 

 ordinary likeness to one of the twigs of its food-plant, 

 and the deception is still further completed by the ability 

 of the insect to support itself by its hinder clasping legs 

 alone, while the body is held out stiffly at a sharp angle 

 with the supporting stem ; and is maintained in an ab- 

 solutely rigid and motionless position for hours at a time. 

 Some support the pull of the body by means of a silken 

 thread, almost invisible, from the mouth to the twig, but 

 more commonly no such aid is used. Thus, when not feed- 

 ing, they become a part and parcel of their surroundings, 

 absolutely invisible. 



Even more remarkable are the caterpillars of the blotched 

 emerald (Euchloris pustulata) and the Essex emerald (E. 

 smaragdana), which attach portions of the food-plant to 

 their bodies, so that, unless they move, they are absolutely 

 indistinguishable from their surroundings. These frag- 

 ments are attached by means of threads of silk to hooked 

 bristles, running down the body. When these deceptive 

 trappings are removed, a reddish-coloured, longitudinally- 

 striped skin is revealed, a coloration in itself protective. 



What strange and subtle influences have been at work 

 to bring about this extraordinary conduct f The question 

 is the more difficult to answer since the young caterpillars, 

 the moment they leave the egg, begin to disguise them- 

 selves, so that parental instruction and imitation are out 

 of the question. More singular still is the fact that some 

 crabs adopt a precisely similar device, attaching pieces of 

 seaweed to a spine-covered shell by means of the big 

 claws ! 



But these disguises are assumed to enable their defenceless 

 wearers to escape the prying eyes of their enemies. Dis- 

 guise, however, has often a more sinister purpose ; and 



