THE RELEASE OF ALARM AND ATTACK BEHAVIOR 
IN SOME NEW WORLD ARMY ANTS 
By William L. Brown, Jr. 
Museum of Comparative Zoology 
Harvard University 
The effect of odoriferous mandibular gland secretions (phero- 
mones) as releasers of alarm behavior in Pogonomyrmex and some 
other ants has recently been investigated by Wilson (1959 and pers. 
commun.). It is not known how widely among the subfamilies of 
ants that the same or an homologous effect may occur, but Wilson, 
myself and others have been able to detect various pungent odors 
originating from the heads of worker ants in the subfamilies Myr- 
micinae ( Pogonomyrmex , Solenopsis) , Ponerinae (Paraponera, Meso- 
ponera , Leptogenys) , and Formicinae (Acanthomyops, Lasius). That 
these substances so often originate in the head is suggestive of a 
similar source and behavioral function, but in most cases experimental 
evidence of their function is lacking. 1 
A recent study trip to the Smithsonian Institution’s Canal Zone 
Biological Area station on Barro Colorado Island" afforded a chance 
to study alarm behavior in the New World army ants (Dorylinae, 
tribe Ecitonini). Since the trip had other primary purposes, the 
army ant observations were rather limited, and some obvious tests 
that suggest themselves, such as trials of interspecific reactions, were 
not carried out. The results obtained, however, do indicate that the 
detailed study of army ant pheromones would be a rewarding one. 
Schneirla (1956 and earlier papers) has made intensive studies of 
the army ants of Barro Colorado, and has outlined many aspects of 
their biology, including the remarkably regular nomadic habits of 
the Eciton species. The first species I studied, E. hamatum (Fabri- 
cius), was also the one given the most attention by Schneirla and his 
colleagues; it is the most conspicuous army ant on the island. 
A trunk trail of E. hamatum was found at midday running along 
the edge of a buttress root of a forest tree. The two-way stream of 
ants varied from two to six individuals in width, and the incoming 
ants bore much booty, mostly the pupae of the fungus-growing ant, 
3 I have found that ants of the Australian formicine genus Calomyrmex 
produce a bright yellow or scarlet droplet at the base of each mandible 
when roughly disturbed, but it is not known whether this substance is odori- 
ferous. 
The trip was supported by a grant from the Milton Fund of Harvard 
University. 
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