164 MANUAL OF VEGETABLE-GARDEN INSECTS 



vine. The pupa is brown, becoming darker with age and is 

 about f inch in length. The insect remains in the pupal stage 

 from a week to ten days in warm weather. In two or three 

 days after emergence, the moths lay eggs for another brood. 

 Reproduction is continuous throughout the season. 



After the tubers have formed, they may become infested 

 in several ways. Some of the caterpillars may leave the stalks 

 and migrate to the potatoes. When the soil is loose and the 

 potatoes are near the surface, the moths may work their way 

 down through the cracks and lay their eggs on the tubers. 

 When the potatoes are planted shallow some of the tubers 

 may become exposed and the moths will lay their eggs on them. 

 Potatoes are most likely to become infested at digging time. 

 If left exposed in the field during late afternoon or overnight, 

 eggs are laid on them in abundance. When the piles of pota- 

 toes are covered with infested vines, the caterpillars may leave 

 the stalks and enter the tubers. When infested tubers are 

 placed in storage, the insect will continue breeding throughout 

 the winter provided the temperature does not fall below 40^ 

 or 50° F. When deposited on the tubers, the eggs are usually 

 placed around the eyes or on the edge of holes made b}^ the 

 larvse. On hatching the young caterpillar soon works its way 

 into the potato, throwing out a small mass of frass through 

 the opening. The young caterpillars at first burrow just 

 underneath the skin but when half grown or more work their 

 way into the flesh, sometimes quite to the center of the tuber. 

 The burrow is lined with a silken tube through which the larva 

 can move back and forth readily. When about to pupate, 

 the larva leaves the tuber and in some crack or corner or be- 

 tween two potatoes spins its cocoon. In storage the insect 

 will continue to breed as long as any potatoes remain in con- 

 dition to serve as food for the larvae. Five or six generations 

 may develop in the course of a year. 



Under storage conditions, a longer period is required for the 



