Kinsey: The Genus Neuroterus 
21 
GALL POLYMORPHISM 
One of the most unexpected discoveries coming from the 
study of this genus is that the galls of a single variety may 
be polymorphic. 
With few exception^, as far as published, each cynipid 
species has been known from only a single type of gall (alter- 
nating generations of higher forms excepted), and we have 
usually felt warranted in determining the species of the gall 
maker from the character of its gall. The gall has appeared 
so typical for the insect that we have agreed that its form 
must be determined by the peculiar physiology of the insect 
rather than by the nature of the plant tissue, and we have 
generally accepted the idea that the galls express the spe- 
cific nature, the generic relations, and the degree of evolution 
of the insect, irrespective of the plant tissue attacked (see 
my summary in 1920, Bull. Amer. Mus. Nat. Hist., XLH, pp. 
365-369). All of this is undoubtedly true to a large extent. 
But it now develops that the plant tissue is to a consideratle 
degree responsible for the form and the amount of hyper- 
trophy of the galls of several species of Neuroterus, as it may 
be also for galls of some other primitive Cynipidse. 
In the following instances, more than one type of gall is 
inhabited by a single Neuroterus. 
5 types by N. quercicola pacificus (hgs. 51, 55, 57, 60, 63). 
2 types by N. quercicola w ashing tonensis. 
2 types by N. minutus (between two varieties) (figs. 
44-46). 
3 types by N. vernus (figs. 24-25). 
2 types by N. duhius clarkex (figs. 53, 54). 
This is probably only a very partial list of the polymorphism 
that occurs in the genus. Detailed accounts are given with 
each of the varieties in the body of this paper. To illustrate 
with the most extreme case yet known: the galls of the 
bisexual generation of N. quercicola pacificus are either flower 
stem or leaf midvein, polythalamous swellings, varying as 
they occur on either Quercus lobata or Q. Douglasii; and the 
agamic generation of the same insect inhabits twigs, either 
not producing a gall or producing a good-sized, woody, poly- 
thalamous gall, or else inhabits acorn cups where a mono- 
thalamous, slight swelling is all that is produced ! 
