Kinsey : Gall Wasp Genus Cynips 
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in part because the wheeleri influence is evident in hybrid indi- 
viduals thruout all but the very southern range of the species, 
and in part because there are broad areas of transition be- 
tween varieties in most parts of the relatively uniform country 
in which they occur. 
The matter is further complicated by the fact that the gall 
characters may bear no more relation to the insect characters 
than the color of a man’s eyes bears to his height. It is true 
that pure populations of varieties pezomachoides and derivatus 
produce only naked galls, advena produces naked to bristly 
galls, and pure wheeleri produces only spiny galls; but galls 
of erinacei and ozark range from naked to spiny, and hybrid 
individuals everywhere produce almost every type of gall. 
Determinations in this group will be possible only upon com- 
parison of large series of insects representing widespread 
localities. At times in our work it has seemed impossible 
that there was any system in the complex populations we were 
examining. Nevertheless, we offer our explanation of this 
group with some confidence because it accounts for all of the 
six thousand insects we have collected from nearly two hun- 
dred localities in 31 states, because an independent re-deter- 
mination of all of our material verifies more than ninety-five 
per cent of the determinations made more than a year ago, 
and because the final solution is, after all, merely a repetition 
of the story of geographic isolation of closely related varieties, 
complicated in this case by a degree of individual and inter- 
varietal (“inter-specific”) hybridization that should satisfy 
even the expectations of a geneticist. 
The present species is the only one in true Cynips that ever 
produces a polythalamous gall, due evidently to the method of 
oviposition of the bisexual female which (acc. Triggerson for 
variety erinacei , q. v.) lays several eggs without changing her 
position on the leaf. But the generic rights of pezomachoides 
seem not so greatly endangered, for there are incompletely 
fused specimens that clearly show on what the polythalamous 
nature of the gall in this species depends. 
The subgeneric position of this insect is discussed in the 
general treatment of Acraspis. 
Cosens (1912, Trans. Canad. Inst. 9:342, fig. 64) interprets 
the histological structure of a gall of variety erinacei of this 
species as follows : 
