1955] 
Creighton — Distribution of Novomessor 
95 
collecting daily in the area between Barstow and Teha- 
chapi. Yet not a single colony of cockerelli was encountered. 
There seemed to be only two possibilities here. Either 
cockerelli had notably decreased in abundance in the west- 
ern Mojave Desert since 1934 or Dr. Cole’s records were 
incorrect. In the hope of clarifying this point I wrote to 
Dr. Cole for further information on his 1934 records. 
Dr. Cole replied that there were no specimens of cockerelli 
from California in his collection at present. It seems 
virtually certain, therefore, that the above records were 
based on field identification only. The writer believes that 
they were the result of the misidentification of abandoned 
nests of V erow.essor pergandei. This ant is abundant in 
most parts of the Mojave Desert. It makes nests which 
might be mistaken for those of cockerelli and it often 
abandons them. Whether this explanation is correct or 
not, it should be clear that at present there is no reliable 
evidence to show that cockerelli occurs in California. If 
it does so, it seems certain that its occurrence in that 
state will be limited to the eastern end of the Mojave 
Desert. In the writer’s opinion it is safe to conclude that 
none of the range of cockerelli lies west of Longitude 115° 
and only a very small part of it lies west of Longitude 114°. 
The northern limit of the range of both cockerelli and 
albisetosus seems largely determined by the inability of 
either species to occupy highland areas in northern and 
central Arizona and New Mexico. Southeast of Wicken- 
berg, Arizona, the range of both cockerelli and albisetosus 
runs along the southern end of the region where the 
rise to the Mogollon Mesa begins. This area is much 
broken up by valleys and canyons and it seems certain 
that the northern limit of the range is much more irregular 
in this area than our present records indicate. For most 
of these have come from the easily accessible southern 
end of the area. The Mogollon Mesa itself forms an 
effective northern barrier, for its elevation is too great 
to permit either cockerelli or albisetosus to reach the top 
of the plateau. In eastern Arizona and western New 
Mexico the limit of the range dips even further to the 
south, passing below the southern end of the Blue Moun- 
