THE NYMPHS 113 



surface of the leaf-blade and leaving the network of veins 

 untouched. 



These caterpillars continue to feed in this manner for 

 about a week, remaining side by side when feeding, and 

 marching in processions from one leaf to another as the 

 food supply is exhausted. Wherever they go, each spins a 

 silken thread on the surface traversed, so that 

 the combination of all the threads makes a 

 sort of carpet that serves as a foothold for 

 the caterpillars. At the end of the week 

 they moult or cast their skins, a process in 

 which the skin of each larva splits open 

 along the back, and the larva crawls out 

 covered with a new skin that had been formed 

 beneath the old one. This new skin stretches ing-cioak, laid in 



a cluster on a twig. 



somewhat after the caterpillar emerges, so (^™°^ HoUand). 

 that the insect is able to increase considerably in size. 

 At the period of moulting, the caterpillars remain quiet 

 for a short time, but they soon become active again and 

 begin feeding with increased voracity. 



During the next three weeks, this moulting process is re- 

 peated three times, the caterpillars becoming larger each 

 time, and leaving their cast skins upon the denuded twigs. 

 They soon scatter more or less over neighboring leaves, 

 but remain in closely associated colonies. As they increase 

 in size, they eat more and more of the leaf substance; when 

 half grown, they devour all but the mid-rib and the side 

 veins; but when they get larger, only the midribs are left. 



The carpet web that they form becomes more conspicu- 

 ous as the caterpillars become full grown. They then 

 leave the tree or shrub on which they have been feeding, 

 and scatter about, seeking some sheltered situation. Hav- 



