224 INSECTS INJURIOUS TO VEGETATION. 



middle of June till after the beginning of July, upon sweet-scented 

 flowers, which it visits during the middle of the day. Its flight 

 is vigorous and rapid, and its strength is so great that it cannot be 

 captured without danger of its being greatly defaced in its strug- 

 gles to escape. The females lay their eggs, singly, on the leaves 

 of the common locust-tree {Robinia jjseudacacia) ^ and on those of 

 the viscid locust {Robinia viscosa) , which, is much cultivated here 

 as an ornamental tree. The caterpillars are hatched in July, and 

 when quite small conceal themselves under a fold of the edge of 

 a leaf, which is bent over their bodies and secured by means of 

 silken threads. When they become larger they attach two or 

 more leaves, together, so as to form a kind of cocoon or leafy case 

 to shelter them from the weather, and to screen them from the 

 prying eyes of birds. The full-grown caterpillar, which attains 

 to the length of about two inches, is of a pale green color, trans- 

 versely streaked with darker green, with a red neck, a very large 

 head roughened with minute tubercles, slightly indented or fur- 

 rowed above, and of a dull red color, with a large yellow spot on 

 each side of the mouth. Although there may be and often are 

 many of these caterpillars on the same tree and branch, yet they 

 all live separately within their own cases. One end of the leafy 

 case is left open, and from this the insect comes forth to feed. 

 They eat only, or mostly, in the night, and keep themselves 

 closely concealed by day. These caterpillars are very cleanly in 

 their habits, and make no dirt in their habitations, but throw it out 

 with a sudden jerk, so that it shall fall at a considerable distance. 

 They frequently transform to chrysalids within the same leaves 

 which have served them for a habitation, but more often quit the 

 trees and construct in some secure place, a cocoon of leaves or 

 fragments of stubble, the interior of which is lined with a loose 

 web of silk. They remain in their cocoons without further change 

 throughout the winter, and are transformed to butterflies in the 

 following summer. The viscid locust-tree is sometimes almost 

 completely stripped of its leaves by these insects, or presents only • 

 here and there the brown and withered remains of foliage, which 

 has served as a temporary shelter to the caterpillars. 



