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[Vol. 94 
midden workers while sorting or repiling the colony refuse pile; and 
nest maintenance workers after they had come out of the nest 
entrance with a piece of sand, put it down, and turned to go back 
into the nest (see Gordon 1986 for detailed description of the four 
activity types). Individuals were marked in the field using Pactra 
“hot fuel-proof” model airplane paint; ants of each activity were 
marked with a unique color. In the course of the field season, a total 
of 3521 individuals were marked: 307 midden workers, 1169 forag- 
ers, 895 patrollers, and 1150 nest maintenance workers. Colonies 
were checked once daily, usually between 8 and 8:30 a.m., for the 
presence of marked ants. 
P. rugosus 
Observations were made near Rodeo, New Mexico in July- Au- 
gust 1986. In one colony, 173 foragers were collected on the foraging 
trail, and marked in the field using Testors PLA paint. On 27 subse- 
quent days, the colony was checked twice daily for marked ants, 
once between 700 and 1000 and once between 1600 and 1800. 
Results 
Table 1 shows the numbers of marked ants observed each day 
subsequent to marking. Exterior workers survive up to 33 days after 
marking (nest maintenance worker, P. barbatus ). 
Figure 1 shows the longevity data for P. barbatus according to 
activity when marked. As a result, the number of colonies observed 
and the total numbers of marked ants both varied as a function of 
number of days since marking. The data in Figure 1 are normalized 
to take this variation into account. Shown are the ratios of numbers 
of ants observed to the numbers of marked ants theoretically avail- 
able to be observed on that day. For example, there were 12 colo- 
nies that were observed 1 1 days after marking, and these colonies 
contained a total of 819 marked foragers. A total of 10 marked 
foragers were observed on the eleventh day after marking. The 
number shown in Figure 1 is 10/819, or 0.0122, that is, the propor- 
tion of all ants marked that were observed. It appears that marked 
nest maintenance workers outlasted marked foragers, which out- 
lasted marked patrollers. 
