NATURAL ENEMIES 93 



by scattering 1,000 specimens of mixed sexes over a 

 garbage heap on September 23d. This, however, was 

 too late in the season, and weekly collections of fly 

 puparia thereafter gave no result. 



The authors found that this parasite hibernates as 

 a full-grown larva in the puparia of the flies, trans- 

 forming to pupa early in the spring and emerging 

 shortly afterwards. As examples of intensive and care- 

 ful study of a given species, the papers on this form by 

 the authors mentioned are excellent. 



The same authors have made a careful study of an- 

 other house fly parasite of this group, known as Pachy- 

 crepoideus dubius. This species was reared in com- 

 pany with the preceding species, and the experiments 

 of the writers indicated that it is a true primary para- 

 site of the house fly. They were unable to make any 

 observations on the biology of the species, except to 

 notice that the adults in three cases emerged from the 

 fly puparium through a single hole with jagged edges. 



Still another parasite of this group, studied by Gir- 

 ault and Sanders, and described in Psyche for August, 

 1910, is Muscidifurax raptor. This is another small, 

 clear-winged species, black in color, which was reared 

 in some numbers from puparia of the typhoid fly at 

 Urbana and Champaign, Illinois. It also breeds in 

 the puparia of other flies, is solitary in its habits, and 

 more sensitive than the Nasonia which the experiment- 

 ers have described so fully. They state that the bio- 

 logical history of the species can be learned with ease 

 in the laboratory, as the females are not at all averse 



