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 uponerroneous 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 thatit is a common parasite of the nun moth (Liparis 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. 
