TACHINID PARASITES OF THE GIPSY MOTH. 



215 



Fig. 38.— Blepharipa scutellata. First-stage larvae: a, Natural size; 6, 

 greatly enlarged; c, c, c, greatly enlarged in situ in atrophied tissue of 

 host. (Original.) 



as illustrated in figures 39 and 40. In this stage the larva breathes 

 through the epiracle of its host, to which the "funnel," which is 

 apparently foimed by the adventitious growth of a main branch of 

 the trachea, is directly attached. 



But few of the parasites, the early stages of which have been studied 

 at the laboratory, exhibit a more clearly defined physiological rela- 

 tionship with their 

 host than does -Ble- 

 pharipa. This re- 

 lationship is com- 

 parable in many 

 ways to that be- 

 tween the cynipid 

 gall-makers and the 

 oak tree which 

 serves as their host. 

 As is well known, 

 many species of cy- 

 nipids are closely 

 restricted to one 

 species of oak, or, 

 at least, to several 

 nearly allied spe- 

 cies, and the same is to be expected of parasites like Blepharipa and 

 others here spoken of as physiological, and thus limited in their host 

 relationships. The gipsy moth itself is comparable to the parasites 



in which the host 

 relations are deter- 

 mined by physical 

 rather than by 

 physiological con- 

 ditions. In its 

 choice of food, al- 

 though it prefers 

 oak to almost any 

 other of the native 

 trees, it can and 

 does attack all or 

 nearly all varieties 

 of deciduous trees, and even conifers and herbaceous plants when 

 necessity demands. 



The development of the Blepharipa is directly correlated to the 

 development of the host, and as a parasite of the gipsy moth, its 

 larva awaits the pupation of the host before assuming the aggressive, 

 and destroying it (PI. XVIII, fig. 1). Its own pupation is accom- 

 plished in the earth (PL XVIII, fig. 2), and the pupa develops adult 



Fig. 39. — Blepharipa scutellata: Second-stage larva in situ in a portion of 

 its tracheal "funnel." Greatly enlarged. (Original.) 



