1910] Girault and Sanders —Chalcidoid Parasites 149 
the pedicel much shorter than the first funicle joint; apical joint spur-like 
(Fig. 4). Abdomen depressed, ovate, sessile, not as long as the thorax, the 
genitalia exserted in death; mandibles and other characters as in the female. 
A genus closely allied to Eutelus Walker and Platymesopus West- 
wood, from both of which it is separated by the single ring-joint of 
the female antenne, as well as more general characters. 
Host RELATIONS OF THE GENUS. 
The type and sole species of this genus, as our records given 
beyond will show, is an important primary parasite of the common 
house fly, of solitary habit and external, attacking the host in the 
puparium stage but not penetrating the body of the inclosed pupa, 
its larva obtaining nourishment through the body-wall of its host 
by means of absorption. Its host relations are therefore very similar 
to those of Spalangia — those species attacking Musca — in that it 
is mostly confined to a single host and is external and solitary in 
habit. But seemingly unlike the species of Spalangia, which we 
consider in another paper, this parasite also occasionally attacks 
other host genera, we having reared it rarely from the puparia of 
both the screw-worm fly, Chrysomyia macellaria (Fabr.) and also 
Phormia regina (Meig.); from the latter in the laboratory as well 
as in nature. Rarely, it was also reared from the larva of both of 
these flies. 
DISTRIBUTION OF THE GENUS. 
We have found this genus in what is practically a single locality 
in Illinois; in the two adjoining towns of Champaign and Urbana. 
In that locality it is common. Other portions of the state have not, 
of course, been explored in reference to it and we have no knowledge 
concerning its distribution in the United States. 
Tue Tyrer SPECIES oF THE GENUS. 
Muscidifurax raptor sp. nov. 
Female. Length variable; maximum length, 2.60 mm.; minimum length, 
1.80 mm.; average length, 2.24 mm.; range, 0.80 mm.; mode, 2.30 mm. 
General color black, with slight senescence, subcorvinus; flagellum deep 
black, appearing slightly greyish from the pubescence; the abdomen with 
some brownish, at base ventrad on segment 3, a yellowish-brown spot on 
each side of the meson, often contiguous forming a transverse yellowish- 
