ORCHARD INSECTS 



313 



each side. The spring canker worm has but a single pan* 

 of pro-legs on the middle of the abdomen, while the fall 

 canker worm has two pairs of pro-legs. The mature cater- 

 pillars enter the soil to a depth of two to five inches, where 

 they hollow out earthen cells in which they change to pupae. 



In old sod orchards where the 

 canker worms are always worst, 

 their pupae may be destroyed by 

 plowing and thorough cultivation 

 during the summer. The most 

 effective means of destroying the 

 caterpillars is to spray with arsenate 

 of lead, three pounds to the barrel, 

 just as the foliage has fairly ex- 

 panded. A second spraying just 

 after the blossoms drop will com- 

 plete the control. 



The Tent Caterpillar* (1,9,43), 

 is common on wayside apple and 

 cherry trees everywhere east of the 

 Rockies. The little caterpillars 

 hatch just as the leaf-buds are ex- 

 panding in the spring and they at 

 once commence their characteristic 

 tent-shaped web at the nearest 

 crotch. All the caterpillars from one 

 egg-mass co-operate in spinning the 

 tent which furnishes them a shelter 

 at night and during cold and wet 

 weather. The tent is gradually enlarged by adding new 

 layers of silk, the caterpillars living beneath the outer layers, 

 but no foliage is included as in the webs of the fall web- 



* Malacasoma americana Fab. Family Lasiocampidce, see page 88. 





FIG. 226. Wingless fe- 

 male moth and egg 

 mass, and winged male 

 moth of the fall canker 

 worm twice natural 

 size. (After W. E. 

 Britton.) 



