Kinsey : Gall Wasp Genus Cynips 
47 
The third body of physiologic data -bearing on the nature 
of species is to be drawn from the host relations of our pres- 
ent insects. Every species of the 93 in the genus occurs on 
white oaks, including, however, oaks of both the groups 
Leucobalanus and Protobalanus of the Trelease classification 
(1924). In common with many other Cynipidae, these in- 
sects thus throw doubt on the validity of separating Protobal- 
anus from the other white oaks. 
The restriction of our genus, as here classified, to the white 
oaks is of especial interest because previous monographs of 
the group (Dalla Torre 1893, Dalla Torre and Kieffer 1910, 
and Beutenmtiller 1911) have included many black oak species. 
Here is an illustration of the importance of basing biologic 
conclusions on sound taxonomic classifications. 
The most significant of the host relations of long phylogen- 
etic standing within the genus may be summarized as follows : 
1. The Pacific Coast subgenus Besbicus represents three stocks, 
multipunctata, maculosa, and mirabilis, which are restricted to the 
groups of oaks centering about Q. lobata, Q. dumosa, and Q. garryana 
respectively. The subgeneric stock must have reached the Sierras, where 
it split into the three stocks, before the Great Basin became arid during 
the Miocene. Today, every individual of all the species of this subgenus 
shows sensory reactions of essentially the same nature as those shown 
by the ancestral stocks many millions of years ago. 
2. Similarly, the ancestral stocks of Cynips echinus and C. guada- 
loupensis, of the Pacific Coast, have perpetuated their host preferences, 
Q. lobata-dumosa and Q. chrysolepis respectively, thruout the 9 species 
which these groups now represent. 
3. One of the most special host restrictions in this genus is that of 
the four species of the Cynips centricola group on Q. stellata. This evi- 
dences the persistence in heredity of a specialized physiologic character. 
4. In the Cynips mellea group, 8 of the 11 species similarly occur 
on Q. stellata. In this case, however, one may find stray individuals on 
Q. alba and other hosts, especially in regions where Q. stellata is rare 
or lacking. 
5. The species grouped under Cynips pezomachoides and C. gem- 
mula are obviously very close relatives. Nevertheless, the seven species 
of pezomachoides east of the Great Plains are confined to Q. alba and 
its close relatives while the three species of gemmula occur on chestnut 
oaks of the Q. Prinus group. The ancestors of each group must have 
been separated on the basis of host preferences, and their descendents 
still maintain the ancestral choice. 
It would appear, then, that species in nature may be differ- 
entiated wholly or largely either on physiologic or morphologic 
