84 



THE FOREST TENT CATERPILLAR 



pillars commonly eat through the leaf in such a way that the 

 outer end drops to the ground. Examples of this sort of injury 

 are shown in Figs. 20, 26, and 27. The result is that in the 

 case of the badly-infested trees the ground beneath is covered 

 with these leaf fragments, which may be heard falling continu- 

 ally as the caterpillars work. This habit causes the insect to 

 be relatively much more destructive than if it simply devoured 

 the whole leaf because the tree is robbed of more of its leaf-sur- 

 face, the damage done being somewhat analogous to that of the 

 cutworms, which eat off the stem of a corn plant without devour- 

 ing the leaves. 



During the moulting periods, as well as during long-con- 

 tinued storms, the caterpillars collect together in great masses, 

 resting upon a silken web attached to the bark of the tree. 

 (Fig. 24.) Here they remain a day or two, until the old skins 

 are sloughed off and the new ones are ready for use. 



The caterpillar of this species is at once distinguished from 



the common American 

 Tent Caterpillar by the 

 differences in the mark- 

 ings of the line along 

 the middle of the back. 

 In the Forest Tent 

 Caterpillar this line is 

 interrupted, consisting 

 of a series of white 

 markings like that 

 shown in the middle 

 of Fig. 22, a, while in 

 the common Tent Cat- 

 erpillar the line along 

 the middle of the back is continuous. (Fig. 28, a.) 



The two species of caterpillars may frequently be found 

 intermingled. Sometimes a brood of the Forest species will 

 collect upon the outside of the tent of the common species. 



When an orchard or grove in which the caterpillars have 

 developed is defoliated, they will migrate to neighboring trees 

 in a way suggestive of the migrations of the Army Worm. 

 At such times thev mav be seen in incredible numbers. 



Fig. 28. American Tent Caterpillar ; a, mark- 

 ings on one ring of the back ; d, markings on 

 one ring of the side. 



