28 
Psyche 
[Vol. 88 
hours. Whenever excavation was stopped to be continued on the 
following day, the nest was covered with a heavy vinyl cloth and 10 
cm deep layer of dirt. This was necessary to keep the inhabitants, 
especially the males, in the nest. A total of 80 P. montanus, 26 P. 
subnitidus, and 20 P. rugosus nests were completely excavated 
between 1977 and 1980. 
It appeared that the excavation procedure disrupted stratification 
of individuals within the nest only slightly. When nest chambers 
were exposed, many individuals emerged, but most of the popula- 
tion remained in the chambers, and assumed a defensive position 
involving opening of the mandibles and forward extension of the 
antennae. 
The numbers of workers at each level and the position of the 
queen were recorded. When the nests were in production, the 
presence or absence of eggs was noted, but the eggs were not 
counted, as they were extremely small and are easily lost in the dirt. 
The larvae, pupae, females, males, and callows (immature, under- 
pigmented workers) were counted when they were present in the 
nests. The contents of each level were summed to obtain an estimate 
of the entire nest population. 
Seed storage in nests. 
The seeds were separated from the soil by filling a 1000 ml beaker 
about full of soil and seeds. The contents were washed into a sieve 
with 0.5 mm mesh. The washing and swirling were continued until 
all of the seeds were removed from the soil. The material caught in 
the sieve was washed again until only seeds remained in the sieve. 
The seeds were then dried (60° C) to constant weight. 
Nest structure. 
In the process of nest excavation it was noted that the general 
form and shape of the nests were comparable in all three species. 
The P. montanus nest structure was studied by pouring a thin 
solution of plaster of Paris (3 tablespoons /liter of water) into one 
nest. The solution was dilute enough that the walls of most of the 
tunnel system were coated with plaster. The nest was excavated in 
1-2 cm layers and the tunnel structure at each layer was measured 
and sketched. The resulting series of “cross sections” of the nest 
resulted in a composite drawing of the nest. 
Nest temperature and humidity. 
Temperature data were recorded from approximately weekly 
