Page:The Gall Wasp Genus Cynips.pdf/72

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 developed in Philonix, the five layers present but the fibrous parenchyma much over-developed in Atrusca, and the collenchyma and epidermal layers constituting most of the gall in Acraspis; distribution entirely east of the Sierra Nevada in North America.

Philonix-Atrusca-Acraspis

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,