WORKER LONGEVITY IN HARVESTER ANTS 
(POGONOMYRMEX) 
By D. M. Gordon* and B. HGlldobler 
Museum of Comparative Zoology, Harvard University, 
Cambridge, Mass. 02138, USA 
Most studies of worker longevity in ants have been made in the 
laboratory (Haskins and Haskins 1980; Porter and Tschinkel 1982). 
In the field, increased energy expenditures, predation, and environ- 
mental fluctuations may all contribute to shorten the life of a 
worker ant. In the few existing studies of worker longevity con- 
ducted in the field, the lifespan of exterior workers was found to be 
extremely short. For example, Schmid-Hempel and Schmid- 
Hempel (1984) found that the half-life of Cataglyphis foragers, after 
they were marked, was only 6 days. 
In harvester ants of the genus Pogonomyrmex, the only existing 
field study of worker longevity demonstrated that the average life 
expectancy of foragers and defenders (ants emerging from the nest 
in response to a disturbance) of P. owyheei is 14 days (Porter & 
Jorgensen 1981). Here we show that these results for P. owyheei 
cannot necessarily be generalized to other species in the genus, and 
that longevity results for the exterior workers engaged in one activ- 
ity, such as foraging, may not apply to exterior workers that do 
other tasks. 
Methods 
P. barbatus 
Longevity data were collected near Rodeo, New Mexico in July- 
August 1987, in the course of other studies of polyethism in P. 
barbatus (Gordon, in prep.). Ants from 38 mature colonies were 
marked. In each colony, 50-100 workers were marked from each of 
the activities under study. Foragers were collected while travelling 
towards the nest on a trail carrying a food item; patrollers were 
collected while circling the nest area in a characteristic, zig-zag 
fashion, and after contacting at least 2 other workers with antenna; 
♦Current address: Centre for Mathematical Biology, University of Oxford, 24-29 
St. Giles’, Oxford OX1 3LB, England 
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