Kinsey: The Genus N euroterus 
15 
N. opacus and N. pulvinus occur on Q, stellata, 
N. cerinus and N, ocularis occur on Q. stellata. 
All of these cases are from Central Texas, where twd 
faunal areas are probably involved, and these may not be 
exceptions to the rule, even tho this is not yet proved by 
working out the limits of these areas. This is evidence of 
considerable weight of the importance of isolation in the 
evolution of species. Even those physiologic qualities which 
are responsible for the restriction of each variety to a single 
host provide a sufficient isolation. Of course isolation is 
probably not the cause of the variation, as much as it prevents 
wide crossing, favors inbreeding, reduces the rigor of any 
struggle for existence, and in other ways favors the develop- 
ment and fixation of a new type. 
Further analysis of the host distributions of American 
Neuroteri are probably of less value because of our lack of 
collection data. Thus, three species, contortus, floricola, and 
decipiens, are know from only a single oak each, but further' 
collecting may be expected to show that their varieties occur 
on related oaks. Sixteen varieties are found on Q. stellata, 
and 12 on Q. alba; no other oak is known to have more than 
7 and several oaks have only 1 or 2 varieties. This is in 
part an expression of the number of faunal areas covered 
by each of these oaks, but also in part a record of the thoroness 
with which we have collected. For the same reasons it is 
premature to analize the distribution of the N euroterus species 
among the groups of white oaks. The definition of these 
oak groups can probably be made on the basis of cynipid 
affinities, but Neuroterus as yet furnishes only a few sug- 
gestions. For convenience in accumulating data, in my de- 
scriptions I have employed the following very tentative group- 
ing of oaks, based in part on Neuroterus data, in part on the 
several botannical treatments (see particularly Cobb, 1915, 
Proc. Amer. Phil. Soc., LIV, pp. 165-175). 
White oaks, Q. alba 
Q. Chapmanii 
Q. Margaretta 
Q. lyrata 
Q. macro car pa 
Q. stellata 
