ATTACKING THE LEAVES. 261 



found on the army-worm and several other caterpillars. It 

 is about a quarter of an inch long, with a white face, large, 

 reddish eyes, a dark, hairy body, 

 four dark lines down the thorax, 

 and patches of a grayish shade 

 along the sides of the abdomen. 

 The parent fly deposits her eggs on 

 the back of the caterpillar, usually 

 a short distance behind the head, se- 

 curely fastened by a glutinous sub- 

 stance secreted with them. From 

 these hatch tiny grubs, which eat their way into the body of 

 the caterpillar, feed upon its substance, and finally destroy 

 it, the grubs, when mature, escaping from the body of their 

 victim and changing to oval, smooth, dark-brown chrysalids. 

 Usually a large proportion of the caterpillars are infested by 

 this friendly parasite ; otherwise they would soon become a 

 source of much annoyance to grape-growers. 



Where artificial remedies are required, the vines may be 

 syringed with hellebore and water or Paris-green and water, 

 as directed for the larva of No. 140. Hand-picking may 

 alsp be resorted to. 



No. 139.— The Pearl Wood-nymph. 



Eiidryas unio (Hiibner). 



This is a very near relative of Eudryas grata, No. 138, 

 and so closely do the two species resemble each other in the 

 larval condition that it is difficult to distinguish between them. 

 Unio has usually been regarded as a grape-feeding insect, but 

 from recent observations of Mr. Lintner, of Albany, New 

 York, who has found and reared the larva on an entirely differ- 

 ent plant, Euphorbia color atum, it is possible that it may not 

 feed on the grape-vine at all, and that Dr. Fitch, who first an- 

 nounced this as its food-plant, may have mistaken the larva 

 of E, grata for unio. Since there seems to be some doubt 

 about the matter, we shall briefly describe the insect here. 



