Kinsey: The Genus Neuroterus 
111 
varieties, each confined to the single oak; but probably we 
should not recognize as distinct varieties stwo insects differing 
only in choice of host and part of host attacked and (con- 
sequently?) different galls produced. 
A careful comparison of the female of pacificus with the 
female of the lobata twig and acorn galls suggests that the 
two are alternate generations of one species, for the differ- 
ences are few and the similarities are many. As we should 
expect, the galls of the alternate generations differ primarily 
as regards the parts of the oak affected. Breeding records, 
of which I have a good many, agree in showing that the twig 
and acorn gall adults emerge a short time before the leaf and 
flower stem galls appear, and I have repeatedly found the 
flower galls in abundance and in close proximity to the twig 
galls. I have several times found isolated trees which were 
infested by no other Cynipidse except these two. This sim- 
ilarity of insects and galls, the complementary dates of devel- 
opment, and especially their coincident occurrence, is only 
circumstantial evidence for the alternation of these two in- 
sects; nevertheless there can be little doubt of this relation. 
I have all types of the galls from Q. lobata, but only the leaf 
galls with insects and the stem galls without insects from 
Q. Douglasii, and it is possible that not every kind of gall 
develops on the latter oak. It is possible that the agamic 
form of the Douglasii insects is at times in a leaf or petiole 
gall similar to that of the bisexual generation. 
This life history is noteworthy because, simple as it is, 
it is the most extreme development we have yet recognized 
in American species of Neuroterus. More extreme cases are 
known for European species of the genus. The insects of 
these two generations differ somewhat in color and in the 
size of the areolet, characters which cannot be as clearly 
connected with the modes of reproduction as can the size and 
shape of the abdomen. The rather great differences in the 
galls of the generations but emphasize the seasonal dimorphic 
nature of heterogeny. Galls of the bisexual form appear 
very early in spring, when the leaves are just unfolding from 
the buds. Mature galls are on lobata flowers before the leaves 
have attained any size at all, but Douglasii leaves are well 
grown and often of mature size by the time the galls are 
mature. Insects emerge in a very short time, a couple of 
