50 
Psyche 
[June 
years later that additional material of ulcerosus came into 
Wheeler’s hands. In March 1919 he collected, at Oracle, 
Arizona, a small nest of ulcerosus containing both major 
and minor workers. Two years later Wheeler set up the 
subgenus Manniella (2) but he did not assign ulcerosus to 
it. This transfer was made in 1925 by Emery (3) who 
placed bruesi in the subgenus Myrmaphaenus at this same 
time. Emery’s treatment has been followed by students of 
North American ants to the present, although in my 1950 
publication (4) I expressed doubts that ulcerosus could 
properly be included in the subgenus Manniella. 
A fixed idea often has an extraordinarily tenacious hold. 
When I collected six colonies of this ant in Garden Canyon 
in 1950 I still attempted to assign them either to ulcerosus 
or to bruesi. I had studied these colonies in the field as care- 
fully as I could. I had examined a considerable proportion 
of each under a small binocular microscope. I knew that 
the four females which had been taken with them were all 
extremely similar and not at all like the major workers with 
which they had been secured. I knew that in every case the 
structure of the nest was the same. Yet it was not until I 
mounted up this material and studied it in detail that I re- 
alized that ulcerosus and bruesi are the same insect. Since 
others may have equal difficulty in believing that two such 
dissimilar major workers can belong to the same species, 
I have presented here the steps by which this conclusion 
was reached. The altogether unexpected structure of the 
female may be considered first. Except for very minor de- 
tails of color, pilosity, and sculpture all four females are 
identical. Only their cephalic structure need be considered 
at this point. The front of the head of the female shows 
nothing comparable to the oblique truncation of the major. 
The clypeus and the cheeks are, perhaps, a trifle flatter 
than is usual but, in general, the head of the female shows 
the customary, convex curvature found in many species of 
Camponotus (Text-fig. 2). The cheeks show no sign what- 
ever of ulceration. The sculpture of the clypeus, frontal 
lobes and cheeks consists of moderately coarse, oval or 
rounded punctures which are irregularly spaced. The sur- 
face between these punctures is finely and densely granulose. 
