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Indiana University Studies 
epidermal layers, and in all but a few species with an unspecialized 
collenchyma layer; distribution Eurasian and Pacific American. 
Cynips-Antron-Besbicus 
2. Agamic female with normal hypopygial spine not very broad but well 
drawn out at the ventral tip; wings always under 1.35 times the body 
length; galls more diverse, with the collenchyma layer poorly de- 
veloped in Phildnix, the five layers present but the fibrous paren- 
chyma much over-developed in Atrusca, and the collenchyma and 
epidermal layers constituting most of the gall in Acraspis; distribu- 
tion entirely east of the Sierra Nevada in North America. 
Philonix-A trusca- Acraspis 
antron 
BEsmcus 
NIPS 
W PHILO'ttY* 
>ATRUSCA ~ ACRi 
s 
Uj 
A I 
ti. 
FIG. 7. KNOWN DISTRIBUTION, SUBGENERA OF CYNIPS 
Base from Goode series of Base Maps, by permission University of Chicago Press. 
The primary subdivision of the genus into one group that is 
all but exclusively Eurasian and Pacific American, and into a 
second group that is confined to North America east of the 
Sierra Nevada, should have occurred near the center of the 
origin of the genus. We may hypothesize this center in the 
southwestern United States or in adjacent areas of northern 
Mexico. From here the first subgeneric group could have 
moved westward to the Pacific Coast where Antron and 
Besbicus were isolated, and by way of Alaska and Siberia into 
Asia and Europe where the subgenus Cynips developed. The 
second group, differentiated into the subgenera Philonix, 
