1951] 
Creighton — Arizona Ants 
91 
slopes of the mountains, extends from the canyon mouths 
to an elevation of about 7000 feet. 
This evergreen oak area is an interesting one. Shreve 
calls it a “western xeric evergreen forest in which oaks 
are dominant” (3). The term “forest” is apt to mislead 
these who expect a forest to consist of sizeable trees. It is 
only under especially favorable conditions that this associa- 
tion produces a forest in the popular sense. In certain 
areas, however, the evergreen oaks form groves in which 
the trees may be thirty or forty feet high. On the north- 
eastern slopes of the mountains the best stands of evergreen 
oaks occur at elevations of about 6500 feet. At higher 
elevations the groves become increasingly mixed with pines 
until, at an elevation of about 7000 feet, the pines replace 
the oaks. As one descends from the 6500 foot level most 
of the evergreen oaks decrease in size and at the 6000 foot 
level, and below it, they are usually stunted, bushy little 
trees not more than ten or twelve feet high and often much 
smaller. These little oaks frequentlv form dense thickets, 
but the thickets are seldom extensive and generally the 
evergreen oaks at the 6000 foot level are thinly scattered 
over the slopes which rise from the stream bottom. Along 
the stream bottom at this level groves are almost always 
present, but these consist of various deciduous trees and 
large junipers. 
In the area just described I have observed several dozen 
nests of texana. The majority of the nests of this ant 
are situated between the 5500 and 6000 foot levels. The 
area selected is almost always a sunny, open slope, far 
enough away from the stream bottom to be out of the shade 
of the groves which occur there. As a rule the nests are 
placed so that they avoid even the scant shade furnished 
bv the small evergreen oaks. Since the nests are often less 
than fifty yards away from areas of heavy shade, it seems 
clear that the nest-founding female prefers sunny places to 
shady ones. Above the 6000 foot level the incidence of 
the colonies decreases as the elevation increases. For 
practical purposes the upper limit of the range is reached 
about the 6500 foot level. I have found one nest of texana 
at an elevation of 6700 feet but the incidence of nests above 
