62 GYPSY AND BROWN-TAIL MOTHS. [Jan. 



sect abroad, and of the fact that it has been received in con- 

 siderable numbers each year since the work of parasite intro- 

 duction was begun, it has been found impossible to procure 

 enough healthy adults to form a colony of a size sufficient to 

 form a fair test of its economic value as a parasite. This is 

 due to the great difficulty in keeping the pupse over winter, 

 under the necessarily artificial conditions accompanying their 

 collection and transportation. The maggots, after their emerg- 

 ence from the caterpillars, normally enter the ground to a 

 considerable depth. Here they should remain undisturbed 

 until their final transformation to the fly in the following 

 spring; and it has been the experience at the laboratory that 

 any disturbance to which they may be subjected during this 

 period is followed by a rate of mortality amounting, in the 

 several years since their introduction has been attempted, to 

 from 90 to 98 per cent. The cause of this appalling death rate 

 is not altogether apparent. It is hoped that it will be materially 

 lessened in the case of the thousand or more pupse now on hand ; 

 but should these hopes prove futile, it will be only a question 

 of time and additional expense before a satisfactory colony of 

 the insect is established. 



In 1908 about 100 healthy individuals of this species were 

 liberated near Melrose. The species was not recovered in the 

 considerable collections made in the vicinity of the colony the 

 same season; but the fact was not at all to be wondered at, 

 from the relatively insignificant number of the parasites as 

 compared with the many millions of gypsy moth caterpillars 

 which were present in the area over which the parent flies 

 would be expected to fly. There is, therefore, a possibility that 

 the insect has already gained a foothold in America. 



Blepharipa, while possessing more promise than the majority 

 of the numerous species of Tachinids imported or attempted 

 which have been secured in larger or smaller numbers, is only 

 one of several scarcely less promising, and it is hoped that 

 several others will successfully be introduced and acclimated 



V 



in the course of the coming season. Several of these which 

 have already been imported and colonized have also been re- 

 covered from collections made in the field. One of these, 

 Parexorista clidonio*, while entirely different from Blepharipa 



