HYMENOFrERA 



67 



FJG. 57. Thalessa boring in an ash tree to 

 deposit its eggs in the burrow of a horn-tail 

 larva, a wood borer. Photograph, nat- 

 ural size. 



the larvae may feed on 

 wood-boring larvae. . Ich- 

 neumon flies render great 

 service to agriculture by 

 keeping in check the 

 harmful caterpillars. 



Chalcis Flies 



The chalcids have 

 habits similar to the ich- 

 neumons from which they 

 may be distinguished by 

 the outward bend of the 

 antennae and the almost 

 entire absence of veins 



in the fore wings. They are all small, being from an eighth 

 of an inch to a fourth of an inch long. Large numbers of 



them may be se- 

 cured by collecting 

 a dozen or two 

 cabbage worms 

 (Fig. 67) in au- 

 tumn and feeding 

 them daily with 

 fresh cabbage 



FIG. 58. A bunch of five chalcid larvae on the canker i WitViin 



worm. Photograph, twice natural size. leaves. 



a week chalcid 



larvae will be seen to issue from several and spin cocoons 

 immediately in which they may remain all winter or if early 

 in the season transform to pupae and adults in about two 

 weeks. Three out of every ten oak galls in late summer 



