1984] 
Gordon — Pogonomyrmex badius 
255 
using an ocular micrometer calibrated in 0.1 mm. Measurements 
were estimated to the nearest 0.01 mm. The data were subjected to a 
two-way analysis of variance (Sokal and Rohlf 1981), which tested 
for the effect of activity and colony of origin on head width and for a 
colony-activity interaction. 
Results 
A-C. Continuity of role. In both observation periods, the ratio 
of marked to unmarked ants depended highly significantly on activity 
in all five colonies (two-way chi-squared test, p < 0.000 1 for all tests). 
Table 2A shows the data from the first, 35-day observation period 
(part A). The deviations shown are based on the expected values 
derived in the two-way test for each colony. The significance values 
along the diagonal of the table are the result of the two-by-two 
chi-squared tests of whether marked ants continued to do the tagged 
activity. These results all show highly significant, positive deviations 
from the expected values. All groups of ants continued doing the 
activities that they were doing when marked. Thus, the data of Table 
2A show that groups of ants do specialize in certain activities. 
Cells not on the diagonal in Table 2 A show the data for ants in the 
four activities other than the tagged one. In some cases, the data show 
a large positive deviation from the expected value in an activity other 
than the tagged one. This indicates that marked ants were likely to 
perform a second activity as well as the tagged one. The results shown 
in Table 2A, and summarized in Table 2C, lead to the following 
conclusions. 
Ants marked while doing midden work tended to be later engaged 
in patrolling, and vice versa, indicating that midden work and patrol- 
ling are done by the same ants. Ants marked while convening later did 
midden work as well. But ants marked doing midden work did not 
later do convening. Similarly, ants marked while doing nest mainte- 
nance later did patrolling as well. But ants marked while patrolling 
did not later do nest maintenance. These results suggest that ants 
marked while convening were in transition to midden work, and that 
ants marked while doing nest maintenance were in transition to 
patrolling. In these two colonies, I examined the proportions of 
marked ants doing each activity as a function of time in the course of 
the first observation period, but saw no interesting or possibly signifi- 
cant changes in these proportions. The possibility of later role 
