TACHINID PARASITES OF THE GIPSY MOTH. 229 



establishment of Tricholyga will depend upon the existence of an 

 alternate host, and its effectiveness as a parasite upon its ability to 

 make a place for itself in the established American fauna. Several 

 attempts to secure its reproduction in the laboratory on other hosts 

 than the gipsy moth have been measurably successful, and there is 

 good reason to believe that it will find conditions suitable to its con- 

 tinued existence here. 



Notwithstanding its similarity to Tachina it appears to be a per- 

 fectly good and distinct species, and since it is not known to be 

 represented by any very close ally in America, the objections which 

 have been raised against the probable establishment of Tachina do 

 not apply. 



It is unfortunately impossible to say more concerning the likeli- 

 hood of its becoming established here, since there is much doubt con- 

 cerning its colonization. If, as is possible, it formed the bulk of the 

 so-called Tachina liberated in 1906 and 1907, it ought to have been 

 recovered before now: if, on the contrary, it was sparingly present 

 among the tachinids reared and liberated during those years, there is 

 no reason to expect its recovery before 1911, and perhaps not until 

 1912, as the direct result of the large colonies which were liberated 

 in 1909, and which would represent the first satisfactory colonization 

 of the species in America. 



In the popular bulletin issued in the spring of 1910, through the 

 office of the State forester of Massachusetts, it was stated that in the 

 fall of 1909 it had already been recovered upon several occasions as a 

 parasite of the gipsy moth, and under such circumstances as to make 

 it possible that it was already established and dispersing rapidly. 

 This statement was in part at least based upon erroneous identification, 

 but at the present date it is expected that 1911, or at the latest 1912, 

 will see its recovery under bona fide circumstances as an established 

 and promising parasite of the gipsy moth. 



PARASETIGENA SEGREGATA ROND. 



A third species of the group which includes Tachina and Tricholyga, 

 and which deposits similar large, flattened eggs, is to be found in 

 Parasetigena segregata, which occurs throughout Europe in very 

 variable abundance as a parasite of the gipsy moth, but not of the 

 brown-tail moth. It is the one species of gipsy-moth parasite which 

 appears to be more common toward the northern limits of the range 

 of this particular host a fact which may be explained in part by the fact 

 that it is a common parasite of the nun moth (Porthetria monacha L.) 

 as well. It differs from either Tachina or Tricholyga in that it has but 

 a single generation a year. It hibernates in the puparium and the 

 flies issue coincidently with or perhaps if anything a little in 

 advance of ; those of Blepharipa in the spring. 



