Kinsey : Gall Wasp Genus Cynips 
73 
supply a present-day means of eastern migration for only 
those species of Cynips that occur on the Gambelii-macrocarpa 
oaks. There are two such species, Cynips villosa and C. hirta. 
Villosa may, for all that is now apparent, have crossed from 
the more northern Rockies. On the other hand, the more 
southern concentration of the varieties of C. hirta, in part 
upon the chestnut oaks, suggests that this species came east- 
ward by the Colorado-Missouri route which, we shall show in 
a moment, was followed by the remaining species of the 
genus. Any cak-inhabiting cynipid that crossed in this part 
of the Plains must have done so before the extermination of 
the oak flora in those areas in the Pliocene. 
It is possible that during the southernmost extensions of 
the glaciers of the Pleistocene some increase in moisture 
allowed oak to return to some southern parts of the Great 
Plains. It is certain, however, that the several stocks of 
Cynips had come east before then, because in the northern 
Middle West there are several species which, as we have 
shown (page 59), seem to have had a hybrid origin in the 
Pleistocene. If the southern extension of the glaciers at that 
time crowded northern varieties into the ranges of southern 
varieties of the same species, with consequent hybridization 
of the close relatives, it follows that northern and southern 
varieties were already differentiated in the eastern United 
States. 
Altho eastern and western species of oak make rare con- 
tacts in the Texas Panhandle and in northeastern New 
Mexico, the affinities of all the Cynipidae of Texas east of 
the Pecos River are clearly with those of the eastern United 
States, while all the Cynipidae of West Texas are of more 
direct origin from the Arizona-New Mexico stocks. The 
geologic record indicates that the desert boundary between 
West Texas and the more eastern part of the state is more 
ancient than the genus Quercus. One may conclude that the 
cynipid fauna of eastern and central Texas has been derived 
from the north and east and not directly from the Southwest. 
The present-day concentration of the species of Acraspis 
(fig. 49) indicates that the eastern migration did not occur 
very far north of Texas. It probably occurred in Kansas and 
Missouri, or not far north or south of the boundaries of those 
states. 
