Page:The Gall Wasp Genus Cynips.pdf/66

 a wheeleri x pezomachoides cross in the Cumberland Highlands and the Appalachian areas of central and eastern Tennessee, North Carolina, northern Georgia, and the borders of adjacent states in the South. Individuals that are certainly hybrids between wheeleri and pezomachoides are common from northern New England to Georgia wherever wheeleri still comes into contact with pezomachoides. Such hybrid individuals may be interpreted with much certainty and they confirm our explanation of advena in the Southern Highlands. The unusual amount of variation, the occurrence of segregates that appear as pure wheeleri or pure pezomachoides, and the geographic position of the hybrid between the supposed parents is, as with erinacei, the basis for recognizing the origin of advena. Segregates of wheeleri are more common in advena than in erinacei, probably because advena is not yet free from current contributions from the nearly pure populations of wheeleri which occur in the southern mountains. The galls of advena are interesting because they run largely to the smooth form typical of pezomachoides, indicating some dominance of pezomachoides characters; but advena galls are very finely bristly, and large series do include a few that are as strictly spiny as those of wheeleri.

We have then, out of the 93 species in the genus, the following which we would recognize as of hybrid origin: