1915} North American Pachygasterine 307 
might be considered as generically distinct from both Pachygaster 
and Neopachygaster. Dr. Sharp’s suggestion to this effect is 
disposed of by Verrall in dealing with Neopachygaster, and in 
his notes under P. tarsalis he mentions a specimen of that 
species which has the fork of the third vein ‘“‘so indistinct as 
to be almost absent.’’ In this connection it seems reasonable 
to indicate that in several genera in this family the absence 
or presence of the fork of the third vein is not considered as of 
more than specific value. This is noticeably true in Nemotelus 
and Oxycera, where one finds that even in recent papers the 
presence or absence of the fork is not used even as a primary 
key character for the species. To be consistent, one who 
accepts this character as of generic value in Pachygasterinz 
would almost as certainly be required to accept it as such in 
the other subfamilies; or, conversely, since this character is 
considered as of specific value only in genera which contain 
a much larger number of species than does Pachygaster sens 
lat., it is inconsistent to accept it as of generic value in the 
latter. 
There is, however, a slight but fundamental difference 
between Zabrachia and such genera as Nemotelus and Oxycera, 
the two latter having the third vein differently formed. In 
this connection see notes on Zabrachia. 
The structure of the head of the male, in which the eyes are 
distinctly separated, is the only character of importance in 
the separation of Neopachygaster from Pachygaster, which 
latter has the eyes of the male contiguous, and it is practically 
impossible for any one but an expert to separate the females 
of the genera. 
The last subdivision of the old genus is that of Kertesz, 
referred to in a subsequent part of the present paper, by which 
the genus Eupachygaster was erected to receive Pachygaster 
tarsalis Zetterstedt. 
I have drawn up a key to the genera of North American 
Pachygasterine as limited in the heading to this paper, which 
should make the situation clear. 
