1910] Girault and Sanders—Chalcidoid Parasites 145 
THE CHALCIDOID PARASITES OF THE COMMON HOUSE 
OR TYPHOID FLY (MUSCA DOMESTICA LINN.) 
AND ITS ALLIES.’ 
III. Description or a New NorruH AMERICAN GENUS AND SPE- 
CIES OF THE FamiLty PTEROMALIDAE FROM ILLINOIS, PARASITIC 
oN Musca domestica Linn., witH BioLocicaL Noves. 
By A. A. GirauLt AND GEORGE ETHELBERT SANDERS, 
The University of Illinois. 
The type species of this new and important genus of the pteroma- 
line tribe Eutelini, was in point of numbers, third among the chal- 
cidoid parasites reared by us during the investigations of the common 
house fly, during the latter part of the season of 1908, it being less 
numerous than species of Spalangia and the parasite Nasonia brevi- 
cornis Ashm. Unlike the latter, however, it was not reared inde- 
pendently or from a number of hosts, but nearly always occurred 
in connection with some one of the species of Spalangia and we were 
inclined to believe, though the evidence was lacking, that it usually 
attacked that genus, and hence is a secondary parasite of the 
typhoid fly, though its réle may also be that of a primary 
parasite. A fact which contributed to our belief of its secondary 
role is the general likeness which it exhibits to Spalangia, a not 
uncommon thing between host and parasite or host and inquiline, 
though by no means the rule. But we have no evidence whatever to 
show that this is the case and are forced to the conclusion that the 
type species of the genus is a primary parasite in every sense. 
In this third paper of this series, the genus is described and con- 
sidered in detail and such biological facts as we were able to observe 
concerning it are also given. This genus, Spalangia and Pachycre- 
poideus dubius Ashm., already considered, are the principal primary 
parasites of the house fly, the species of Spalangia being the most 
numerous and common of the three genera. They will be considered 
in a paper to follow. 

1 Continued from Vol. XVII., p. 117. 
