220 
Psyche 
[Vol. 93 
1A 2A 
YC • 
• YD 
• WH 
• BD 
IB 
BD • 
• YD 
RC • 
Fig. 1 . Spatial relationships of nests placed on floors (each 1 m X 1 m). Additional 
nesting tubes were supplied to give a total of 10 on each floor. 
apparent from censuses when one or two workers were observed 
within a tube (cf. Table 2). Sometimes this exploration was followed 
by immigration, but more often there was no apparent result. 
The time scale within which population changes occurred is given 
in Figure 2. Fighting between workers was most frequent in the first 
three weeks of the season, and virtually nonexistent after 8 weeks. 
Similarly, observations of workers carrying other workers were 
clustered in the first few weeks of the experiments. Exploration of 
new nesting sites was quite high initially, then fell off by the second 
