Kinsey: Gall Wasp Genus Cynips 
399 
favor inbreeding of the hybrids, have developed more uni- 
form populations than a mulatto people of more immediate 
origin would show. 
The typical gall of wheeleri is spiny; the gall of pure 
derivatus is always smooth and naked. The occurrence of 
typical spiny and naked galls in the erinacei population is to 
be explained as the segregation of the parental types from the 
heterozygotic individuals. The occurrence of intermediate 
types of galls is what we should expect if the gall producing 
capacities of the insect are controlled by multiple factors in 
heredity. On the other hand, in the eastern extension of the 
range of erinacei, at least in northern New England and again 
in Virginia, erinacei comes into contact with variety pezo- 
machoides and probably interbreeds with it. It is even pos- 
sible that what we are still calling erinacei is a wheeleri x 
pezomachoides cross in these localities. Pezomachoides and 
derivatus are so similar that I cannot distinguish between their 
influence in a series of hybrid insects, but there is a notable 
difference in the galls from these two hybridizations. Wher- 
ever erinacei comes into contact with pezomachoides, almost 
all of the galls are as naked as those of pezomachoides. There 
are not even as many of the spiny galls in such parts of the 
country as we should expect to segregate from any sort of 
hybridization ; and it is possible that there are hereditary or 
environmental factors which select in favor of the pezo- 
machoides type of gall in such localities. Histologic studies of 
both the naked and spiny forms of the galls of erinacei have 
been made by Cook and by Cosens, both of whom are quoted 
in the general discussion introducing this species in the present 
paper. 
The abundance and the conspicuous nature of the spiny galls 
of erinacei, together with the realization that the agamic, 
short-winged, mid-winter female was probably followed by a 
bisexual, spring generation, has resulted in the accumulation 
of considerable data on the life history of the insect. On the 
basis of laboratory and field observations of insects from spiny 
galls of this variety, Triggerson in 1914 reported, from the 
Entomological Laboratories of Cornell University, the alter- 
nate generation of this insect in one of the most detailed 
studies that we have of the life history of any American 
cynipid. 
The young galls of the agamic form appear late in June 
