TACHINID PAKASITES OF THE GIPSY MOTH. 



225 



rounded out, is not done away with. Unless the parasite hibernates 

 in the brown-tail caterpillars such a host must be found among the 

 native Lepidoptera, and while the number of species available prob- 

 ably runs into the hundreds, they are, with few exceptions, already 

 controlled by their native parasites. Compsilura, if it continues to 

 increase, will have to overcome these parasites in the competitive 

 struggle for possession, and, as already stated, the outcome of this 

 struggle is awaited with interest. Upon it will very largely depend 

 the effectiveness of Compsilura as a parasite of the gipsy moth and 

 the brown-tail moth in America. 



TACHINA LARVARUM L. 



This rather important parasite of the gipsy moth (fig. 43), and to a 

 more limited extent of the brown-tail moth in Europe, is so simi- 

 lar to the Ameri- 

 can Tachina mella 

 Walk, as to make 

 % the separation of 

 the two by struc- 

 tural characters 

 alone difficult at 

 best, and in some 

 instances impossi- 

 ble. It is similarly 

 closely allied to 

 Tachina japonica 

 Towns., and the 

 three species or 

 races appear to oc- 

 cupy about the 

 same position in 

 the natural order 

 of things in the several countries which they inhabit. The European 

 and the American are both quite catholic in their host relations, and 

 while the same can not be said of the Japanese in the present state 

 of our knowledge, it will doubtless be found true when this knowledge 

 shall be more extensive. 



From an economic standpoint Tachina mella and Tachina larvarum 

 are distinct enough specifically, if we are to consider their parasitism 

 from an economic aspect, since the one is habitually and commonly a 

 parasite of the gipsy moth, while the other is not. It would appear that 

 Tachina mella attacks the gipsy moth quite as freely in America as 

 Tachina larvarum does in Europe, but, as has already been mentioned, 

 the attack is not successful from either the economist's or the parasite's 

 point of view. 



62188°— Bull. 91—12 15 



Fig. 43. — Tachina larvarum: Adult female and head in profile. 

 (Original.) 



Enlarged. 



