Kinsey : Gall Wasp Genus Cynips 69 
opinion (1923:140) that “it is very doubtful if there was any 
possibility of an interchange of species of oak between the 
Old and New Worlds after late Eocene or Oligocene times,” 
and this may be the latest origin we may presume for the 
genus Cynips . 
On the other hand, it is difficult to understand why both the 
primary subdivisions of the genus did not spread both to the 
east and to the west of their Southwestern center of origin 
if they migrated very much before the Great Basin became so 
arid as to interpose an effective barrier to further interchange 
of eastern and western species. It is understandable that 
each group might have begun its migration in a particular 
direction, but our knowledge of the present-day distribution 
of organisms would lead us to expect that a group should, in 
sufficient time, radiate in every direction in which there are 
no recognizable barriers to migration. But the rising moun- 
tains of the Pacific Coast probably did not bring about the 
development of the Great Basin deserts until the Miocene. If 
the Eurasian-Pacific- American branch of the genus crossed on 
to the Coast in the Miocene, its failure to radiate in other direc- 
tions might be explained as due to the subsequent develop- 
ment of aridity in the Great Basin before the group had time 
to move back across that area. But if the group must be 
taken out of the Southwest and across Alaska at an earlier 
date, as Berry’s statement would require, it is more difficult 
to understand why the Pacific Coast subgenera did not have 
an opportunity, before the Great Basin became arid, to spread 
back into the more eastern United States. 
In the southernmost mountains of Arizona there is a 
living variety of the Pacific Coast species Cynips (Antron) 
guadaloupensis. This is the only representative of that sub- 
genus known from east of the Sierras, but it is matched by 
a few cases in ether cynipid genera and by a few Pacific slope 
trees, reptiles, and other organisms that have stray relatives 
in southern Arizona. These strays are, however, such close 
relatives of existent Californian species that they are prob- 
ably to be interpreted as more recent arrivals in Arizona 
rather than remnants of the primitive stock before it moved 
westward into California. During the Quaternary the Great 
Basin had a more moist climate than it had had since the 
Miocene, and the area just north of the Gulf of California 
