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 Miiscidifiirax 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 
