98 MANUAL OF VEGETABLE-GARDEN INSECTS 



first on the soft tissues on the underside of the leaves. As 

 they increase in size, tliey become yellowish ^reen in color 

 with (lark markings and consume almost the entire leaf. The 

 caterpillars feed by preference on the older, outer leaves and do 

 not attack the newjer leaves at the center of the plant until 

 the others have been consumed. Their feeding grounds are 

 covered by a slight silken web. The full-grown caterpillar is 

 about an inch in length, yellowish white with a broad black 

 median stripe and a broader sub-dorsal stripe and marked with 

 numerous piliferous spots surrounded by black rings. The 

 larva becomes mature in about three weeks and constructs a 

 silken tube in the ground within which it forms a cocoon and 

 pupates. The winter cocoon is about three times the length 

 of the larva and the summer cocoon only twice as long. There 

 are usually three generations a year and in some cases a small 

 fourth brood may occur. A few of the first, a considerable 

 part of the second, and nearly all of the third generation cater- 

 pillars do not transform till the following spring. The first 

 brood are destructive while the sugar-beet plants are small and 

 easily killed. At this time the crown of the plant is often 

 attacked. When the later broods appear, the plants are larger 

 and rarely killed outright but the size and sugar-content of the 

 roots are greatly decreased by the defoliation of the plants. 

 The third brood is the least injurious because the plants are 

 more nearly mature and the brood is smaller. 



In some regions in which the sugar-beet is grown extensively, 

 the caterpillars often occur in countless numbers and the moths 

 attract attention by flying in clouds over the fields. 



Means of control. 



The sugar-beet webworm may be controlled on sugar-beets 

 by thorough spraying with 3 pounds of paris green in 100 gallons 

 of water to which 6 pounds of whale-oil soap or 3 pounds of 

 lime are added as an adhesive. About 100 gallons of the mix- 



