52 INSECTS INJURIOUS TO THE APPLE 



the outer gummy covering and egg-shell, and deposits its eggs 

 within the egg of the tent-caterpillar, where the young grubs 

 of the parasite hatch and feed upon the contents of the egg- 

 shell of our enemy. A small mite, very similar to that shown 

 in Fig. 31, is also very destructive to these eggs, eating into 

 them and feeding on their occupants. Two larger Ichneumon 

 flies prey upon the caterpillar, Pimpla 

 conquisitor (Say) (Fig. 42) and Ichneu- 

 mon Isetus Brulle, as well as one or more 

 species of Tachina flies, two-winged in- 

 sects a little larger than the common 

 house-fly, similar to Fig. 46. All these 

 latter parasites watch their opportunity 

 when the growing caterpillar is feeding, 

 and deposit their eggs on or under the 

 skin of their victim, which shortly hatch, when the grubs 

 burrow into the bodies of the tent-caterpillars and feed on 

 them, carefully avoiding the destruction of the vital organs. 

 The infested larvae usually reach maturity and construct their 

 cocoons, but after a time, instead of the moth, one or more of 

 these friendly insects make their appearance. Several preda- 

 ceous insects also devour the larvae ; these are referred to in 

 detail under No. 21. 



No. 21. — The Forest Tent-caterpillar. 



Clisiocampa sylvatica Harris. 



This insect closely resembles the common tent-caterpillar. 

 No. 20. The moth (6, Fig. 43) is of a similar color, but 

 paler, or more yellowish. The space between the two oblique 

 lines is usually darker than the rest of the wing, and the 

 lines themselves are dark brown instead of whitish. In the 

 figure, a represents the egg-cluster, c one of the eggs, much 

 enlarged, as seen from the top, d a side-view of the same. 



The eggs of this species may be distinguished by their 

 almost uniforsn diameter and by their being cut off squarely 

 at each end. The number of eggs in each cluster is usually 



