52 
Indiana University Studies 
the phylogenetic history of this genus are correct (see pp. 61 
to 77) these subgenera have been separate since the Miocene, 
a matter of possibly ten to twenty million years. The sub- 
genera originated in the Southwest, where the first subdivi- 
sions must have occurred. The extensions of these stocks out 
of the Southwest must have occurred before the Great Basin 
to the west or the Great Plains to the east became too arid 
to support an oak flora, which would suggest that it has been 
at least a million years since some of these stocks first came 
into their present host-geographic areas. The ranges of these 
species cover continuous instead of discontinuous regions, in- 
dicating that in all of that time no new species has succeeded 
in developing inside the range of any of these old species. 
This does not mean that the species have remained unchanged, 
for mutants developing in the old range and hybridizing with 
the parental types would remake the old species into new, 
hybrid species. But as for the multiplication of species, new 
populations can have developed only near the edge of an older 
range where they could spread into unoccupied territory away 
from the handicaps afforded by close relatives. 
Another source of evidence that new species develop on the 
frontier of the parental range is afforded by the distribution 
of the short-winged species in Cynips. These insects are 
without doubt phylogenetically more recent than their closest 
long-winged relatives. Every one of the nine species which 
occur in southern Arizona and New Mexico, where these stocks 
first developed, is a long-winged species, just as the parental 
stocks undoubtedly were. The 42 short-winged species all lie 
more remote from the center of origin of the genus. Wher- 
ever long-winged and short-winged species exist in the same 
specific stock, the long-winged species are nearer and the 
short-winged species more remote from the Southwest. Thus, 
to cite specific instances, Cynips dugesi has its only long- 
winged representative in southern Arizona and New Mexico, 
and shorter-winged representatives further north in the Rock- 
ies, eastward in West Texas and (C. cava) Central Texas, and 
southward in Central Mexico. Cynips villosa has its most 
southwestern varieties long-winged, with shorter-winged vari- 
eties occurring northward in Arizona, New Mexico, Colorado, 
and Utah, and eastward thru the Middle West. Cynips mel- 
lea, with ten varieties, spreads from the southwest across to 
