252 
Psyche 
[Vol. 91 
Methods 
All experiments were conducted in the laboratory with five queen- 
right colonies of P. badius, each containing about 650 workers. The 
presence of brood inside the nest could not be ascertained. Colonies 
were kept in soil-filled tanks (45 X 25 X 20 cm), and fed with 
Bhaktar-Whitcomb diet (1970), which was placed on the soil surface 
in a small dish. Individual ants were marked with Testors Gloss 
Enamel, each with a drop on the top of the head. Single ants were 
kept isolated overnight after being marked, and then put back into 
the home colony. No adverse reactions to the marking procedure 
were observed. 
All tasks performed by ants outside the nest were classified into the 
following five activities (Table 1): Foraging, Nest Maintenance, 
Patrolling, Midden Work, and Convening. Ants inside the nest were 
not considered in this study. No majors were marked, since they spent 
almost all of their time inside the nest, probably assisting in brood 
care (pers. obs.). 
An observation record consisted of the numbers of marked and 
unmarked ants in each of the five categories of behavior. Observa- 
tions were made between 8:00 and 20:00. Each observation lasted 
5-10 minutes, depending on the total number of ants outside the nest. 
At least one hour elapsed between successive observations. 
A. Continuity of role. In each of the five colonies, ants collected 
while performing one of the five categories of behavior were removed 
from the colony and marked. For example, in one colony only 
foragers were marked, in another only patrollers were marked, and so 
on. In each colony, five ants were marked every five days until 20 ants 
had been marked. Each group of five ants was marked with paint of a 
different color. Thus each colony was observed for a total of 35 days, 
which I call the first observation period. During this time, a total of 
728 observations were made, about 145 observations on each colony. 
The data were analysed separately for each colony as follows. First, 
a two-way chi-squared procedure with four degrees of freedom 
(Sokal and Rohlf 1981) was used to test whether the distribution of 
the ratio of marked to unmarked ants depends on activity. Next, 
another chi-squared test, this time a two-by-two test with one degree 
of freedom, was performed. The latter tested whether ants were 
significantly likely to continue doing the activity they were doing 
when marked, called the “tagged activity.” Both tests used the total 
