14 
Indiana University Studies 
and from England, France, Germany, Denmark, Italy, Hun- 
gary, Austria, Czech o -S 1 ovaki a , Finland, and Russia among 
European countries. This cooperation has been indispensa- 
ble, and specific acknowledgment of my indebtedness to each 
collector is made with each item in the systematic portion of 
this paper. The accompanying map (Fig. 6) will show the 
extensive — albeit still inadequate — sources of our American 
material of Cynipidae. 
The accumulation of these geographic data has received 
some impetus from repeated analyses we have made of our 
held technic. By using the automobile we reach twice as much 
territory in a given time as we were formerly able to reach 
by railroad transportation. We find that the densest popula- 
tions of Cynipidae are, for some reason not yet apparent to 
us, located on isolated oak trees or at edges of woodlands, 
and it is there that we now concentrate most of our efforts 
while in the field. It was some years before we learned that 
the distribution of most species of gall wasps is very local, 
and that it is a waste of time to attempt to make collections 
of populations that are sparsely scattered over the country- 
side. If large populations are not readily available at the 
first stopping place, we take a sample and move a hundred 
yards to a half-mile across country, continuing the procedure 
until we have discovered some tree or thicket heavily laden 
with galls. Many a rural community will bear witness to the 
peculiarities of our conduct in their countryside, but our cabi- 
nets of insects and galls bear more eloquent testimony to the 
effectiveness of this method. 
Because of the peculiar host relations of the higher Cynipi- 
dae, it is necessary to collect from every species of oak in each 
locality in order to obtain a satisfactory set of specimens. To 
avoid being misled, in our interpretations of species, by such 
local populations as might segregate into Mendelian races, we 
make it a point to secure material from separated trees of each 
host wherever possible. Our returns are more than doubled 
when two of us work together in the held. We have given 
from a few hours to several days to the exploration of each 
locality, but upon careful accounting we find that, with two 
or more of us working together, we can take a fair sample of 
a region in four or hve hours. 
In order to secure approximate data on the furthest exten- 
sion of the range of each species, we do not make our col- 
