50 INSECTS INJURIOUS TO THE APPLE. 



times when not feeding. In five or six weeks they become 

 full grown, and then measure about an inch and three-quarters 

 in length, and present the appearance shown in Fig. 41. The 

 body is hairy and black, with a white stripe down the back, 

 and on each side of this central stripe there are a number of 

 short, irregular, longitudinal yellow lines. On the sides are 

 paler lines, with spots and streaks of pale blue. The under 

 side of the body is nearly black. 



These caterpillars have regular times for feeding, issuing 

 from the openings in their tent in processional order, usually 

 once in the forenoon and once in the afternoon. In very 

 warm weather they sometimes repose upon the outside of the 

 nest, literally covering it and making it appear quite black 

 with their bodies. They are very voracious, and devour the 

 leaves of the trees they are on with great rapidity ; it is esti- 

 mated that each larva when approaching maturity will con- 

 sume two leaves in a day, so that every day that a nest of such 

 marauders is permitted to remain on a tree there is a sacrifice 

 of about five hundred leaves. Where there happen to be 

 several nests on one tree, or if the tree itself is small, they 

 often strip every vestige of foliage from it, and in neglected 

 orchards the trees are sometimes seen as bare of leaves in 

 June as they are in midwinter. As the caterpillars arrive at 

 maturity they leave the trees and wander about in all direc- 

 tions in search of suitable places in which to hide during 

 their chrysalis stage. A favorite place is the angle formed by 

 the projection of the cap-boards of fences or fence-posts. 



Here they construct oblong oval cocoons (Fig. 41, d) of a 

 yellow color, formed of a double web, the outer one loosely 

 woven and slight in texture, the inner one tough and thick. 

 In its construction the silk is mixed with a pasty substance, 

 which, when dry, becomes powdery and resembles sulphur in 

 appearance. Within these cocoons the larva? change to brown 

 chrysalids, from which, in about two or three weeks, the 

 moths escape. This insect feeds on many different trees, but 

 is particularly fond of the apple and wild cherry. 



