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. 



Relatively 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 

 disappointment 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 way so significant as would have been the failure in the case 

 of Blepharipa. 



