230 
PARASITES OF GIPSY AND BROWN-TAIL MOTHS. 
Consequently it possesses the material advantage of being in- 
dependent of an alternate host, and theoretically there is nothing 
to prevent its rapid increase whenever conditions favor the increase 
of the gipsy moth. The most that can be said against it is its in- 
ability to effect the control of its other and apparently more favored 
European host, the nun moth, which to a greater extent than the 
gipsy moth is a pest in the forests of northern and central Europe. 
Perhaps it may find conditions in America more favorable than 
in Europe, and thereby be able to do more toward effecting the con- 
trol of its host here than abroad. 
So far as known its larval habits agree very exactly with those of 
Tachina in all of their essential particulars. It leaves the host 
caterpillar before pupation, and only upon rare occasions is carried 
over into the pupa. 
The first specimens which were reared in connection with the 
work of parasite introduction were found mingled with those of 
Blepharipa, which issued from hibernated puparia in the spring of 
1908. There were only a very few of them, but there were enough 
to make it possible for Mr. Townsend to determine the salient features 
in its life history and to create a desire to secure more for colonization 
purposes. 
Kelatively very few puparia were secured in importations of 1908, 
and it remained for those of 1909 to produce the number which was 
necessary to make a satisfactory colony of the species possible. Its 
puparia being indistinguishable from those of Tachina and Tricholyga, 
it was necessary to await the emergence of those species before 
attempting to count upon Parasetigena, but after the others of the 
Tachina group had ceased to issue, it was found that a very satisfactory 
number of unhatched and healthy puparia remained. This number 
was subsequently increased by the importation of several hundred 
which had been reared from the nun moth, and which subsequently 
proved to be specifically identical with, or at least indistinguishable 
from those from the gipsy moth. 
For the most part these puparia successfully hibernated, and in 
excess of 1,000 of the flies were reared in the spring and colonized 
in one locality where there was every opportunity for them to mul- 
tiply to the limit of their powers upon the gipsy moth. An attempt 
to recover the species in the locality later in the season failed, but 
since it was not expected that it would be recovered so soon the 
disa ppointment was not very keen. It would undoubtedly be more 
encouraging from a practical standpoint if it were positively known 
that the species was reproducing freely, but the failure to recover it 
is in no w&y so significant as would have been the failure in the case 
of Blepharipa. 
