84 
Psyche 
[June 
in a phragmotic capacity only. Some of the majors regularly 
leave the nest to forage with the medias and minors. 
A few other observations may be added. Workers return- 
ing to the nest always go in through the aperture head- 
first. They will do so even when this involves considerable 
struggle with what they are carrying. In the event that 
some strange ant is on or near the shield, the returning 
ulcerosus workers make no effort to enter the nest. They will 
wander about nearby until the intruder leaves, at which 
time they will secure entry to the nest in the usual fashion. 
It is clear that ulcerosus is a very timid ant. It is much 
afraid of several smaller species, particularly Xiphomyrmex 
spinosus insons. If the two meet, the Xiphomyrmex will 
usually rob the ulcerosus worker of anything it is carrying. 
This may be the reason why the workers of ulcerosus, which 
are returning to the nest with food, will take a needlessly 
tortuous course over grass tufts. Such a course would 
minimize the chance for encounters with Xiphomyrmex, 
for the latter ant rarely leaves the surface of the soil when 
foraging. 
Presented below are several records which add to the 
known range of ulcerosus : 
Arizona: Huachuca Mountains, Carr Canyon, 5400'; 
Santa Rita Mountains, Sweetwater, 5800'; Chiricahua 
Mountains, Nat. Mon. Campground, 5400'. 
Chihuahua: Sierra de en Medio, Nogales Ranch, 5000'. 
Sonora: Cerro San Jose (Naco) 5100’. 
