TACHINID PARASITES OF THE GIPSY MOTH. 231 



Blepharipa, which was colonized in the same locality and under 

 the same circumstances and subsequently recovered, does not leave 

 its host until after the latter has pupated, and since the collection 

 of pupse is very much less difficult than the collection of caterpillars, 

 its recovery was that much more easy and certain. Although 

 upward of a dozen Blepharipa were secured from collections made 

 in this colony, all of them were from pupse and none from the cater- 

 pillars, which had to be depended upon for Parasetigena. 



A determined effort will be made to recover both species in 1911, 

 and the results of the season are anticipated with much interest. 



CARCELIA GNAVA MEIG. 



This is probably the least understood of the tachinid parasites of 

 the gipsy moth. It appears to be not at all well distributed through- 

 out Europe and has never appeared in sufficient abundance to give 

 it rank as among the important parasites except in the material 

 from southern France. From that region it has been secured in 

 sufficient numbers to make its colonization possible on a scale that 

 is quite as satisfactory as the colonization of Tricholyga, or, for that 

 matter, of Compsilura until after Compsilura was found to be estab- 

 lished. 



It was received in gipsy-moth caterpillar importations as early as 

 1906, but in very small numbers in that year, and in still smaller 

 numbers in 1907 and 1908. In 1909 the very large and until then 

 unprecedented importations from the Hyeres region produced several 

 thousands of flies, and more were received in 1910, which went to 

 strengthen colonies of the previous year. Curiously enough, in 1910 

 it was almost the only tachinid parasite secured from this region, 

 on account of which the gross number colonized is in excess of any 

 other species. Like Tachina, Tricholyga, and Compsilura, it is 

 practically certain that an alternate host will be a requisite if it is to 

 complete its seasonal cycle in America. If this disadvantage can 

 be overcome, there is every reason to expect its recovery in 1911 or 

 1912. That it was not recovered in 1910, in spite of the fact that 

 some 10,000 caterpillars of the gipsy moth were collected in the 

 immediate vicinity of the most satisfactorily liberated colour of the 

 summer before, entirely loses its significance when it is taken into 

 account that neither was Compsilura recovered from these 10,000 

 possible hosts, and Compsilura was also colonized at the same time 

 and in the same place and under circumstances very much more 

 favorable to its establishment than those which accompanied its 

 original and effective colonization two or three years before. Better 

 than Compsilura has done is expected of none of the tachinids, and 

 neither Tricholyga, Carcelia, nor Parasetigena, nor Zygobothria, 



