. PARASITES OF LARGER BROWN-TAIL CATERPILLARS. 297 



ican hosts. This was accomplished by Mr. Titus in one of the large 

 out-of-door cages in 1906, and again with somewhat more success in one 

 of the smaller indoor cages in 1907. As with Compsilura, only two 

 weeks are required for the larval development, a week or ten days for 

 the pupal stage, and three or four days for the female to reach her 

 full sexual maturity. As is also true with Compsilura the larvae are 

 deposited by the female beneath the skin of the host caterpillar. 



Several small colonies were planted by Mr. Titus in 1906, followed 

 by several more small ones and one larger one in 1907. None was 

 liberated in 1908, but in 1909 one very large and satisfactory colony 

 was put out. In 1910 only a single specimen of the parasite was 

 received from abroad and this, curiously enough, in a shipment of 

 gipsy-moth caterpillars. 



It was confidently expected that in 1910 at least a few specimens 

 would be recovered from the field as a result of the earlier colonization 

 work, but these expectations were not realized. Of all of the tachinid 

 parasites of the brown-tail moth, not excepting Compsilura concinnata, 

 it was the one most satisfactorily colonized in 1906 and 1907, and on 

 this account it was expected to find it established in the field. 



It is considered as one of the most likely of the as yet unrecovered 

 parasites to be recovered from the field in 1911 or 1912. 



PAREXORISTA CHELONIiE ROND. 



No brown-tail moth material was received from abroad during the 

 summer of 1905, and consequently nothing was known of the hiber- 

 nating tachinids which attack this host until the spring of 1907, 

 when they began to issue from the puparia of the previous summer's 

 importations. All that were reared that spring were of the one 

 species, which has since been determined as Parexorista chelonise 

 Rond., and to date no other species hibernating as a puparium and 

 with but one annual generation has been reared from this host. 

 Nothing to compare with the difficulties which attended the hiber- 

 nation of the principal gipsy-moth parasite having similar habits 

 was encountered in the case of Parexorista. Its puparia (PL XX, 

 fig. 4) were carefully covered with earth the first winter and the 

 second, but it was then found that this precaution was unnecessary 

 and that the percentage of emergence was quite as large when the 

 puparia were kept dry as when they were damp. The difference 

 appears to be associated with the state in which the pupae themselves 

 hibernate. Those of Blepharipa and Crossocosmia develop adult 

 characters in the fall, and it is in reality the unissued adults which 

 hibernate. Those of Parexorista do not develop adult characteristics 

 until spring, and besides in Parexorista the space between the pupa 

 or nymph and the shell of the puparium is dry and does not, as in 

 Blepharipa, contain a small quantity of colorless liquid. 



