PSYCHE 
Vol. 77 
December, 1970 
No. 4 
RECRUITMENT TRAILS IN THE HARVESTER ANT 
POGONOMYRMEX BADIUS 
By Bert Holldobler and E. O. Wilson 
Harvard University, Biological Laboratories 
Cambridge, Massachusetts 02138 
Introduction 
Pogonomyrmex is the most abundant and specialized genus of 
harvester ants in North America. The workers mainly collect seeds 
for food,. but they also carry dead insects into their nests. In view 
of the great abundance of these ants in many parts of the United 
States ('Cole 1968), the ease with which they can be cultured in 
the laboratory, and their considerable economic importance, sur- 
prisingly little has been learned to the present time concerning their 
communicative behavior. Most attention has been focused on alarm 
behavior. Wilson (1958) discovered that alarm responses are re- 
leased in workers of the Florida Harvester Ant ( P . badius) by a 
pheromone produced in the mandibular gland of the ant. This 
behavior ranges, according to the stimulus intensity and duration, 
from mild attraction to attack and prolonged digging in the soil. 
In 1966 McGurk et al. identified the pheromone as 4-methyl-3- 
heptanone and also detected it in P. barbcitus, P. calif brnicus, P. 
desertorum, P. occidentalis and P. rugosus. Although in many ant 
species chemical trails laid down by worker ants are the essential 
signals for the initiation of mass foraging behavior in nestmates (see 
review by Wilson 1971), they have not yet been implicated (or 
even suspected) in Pogonomyrmex. This article reports the dis- 
covery and subsequent analysis of such a recruitment system in 
Pogonomyrmex badius. 
Materials and Methods 
Field work was conducted in Tampa, Florida, in an open held 
near the campus of the University of South Florida. Laboratory 
experiments at Harvard University utilized three large colonies of 
Pogonomyrmex badius housed separately in two sand-filled terraria 
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