176 
Psyche 
[Vol. 92 
many ants at an early stage of growth after the first brood has been 
raised by the queen, E.O. Wilson: pers. comm.) is the tendency for 
the queen to be very sensitive to disturbances. While the workers of 
Acanthomyrmex ants are usually timid, the queen of A.ferox (and 
presumably also A. notabilis) is exceptionally shy: she often rushed 
out of the nest at the slightest sign of trouble, leaving her workers, as 
yet undisturbed, behind her. 
Harvesting ants. Nests of the species A. notabilis have seed 
stores, and therefore at least this Acanthomyrmex clearly joins the 
select group of species commonly referred to as “harvesting ants.” 
Harvesting ants are most diverse and abundant in xeric situations. 
The cosmopolitan genus Pheidole , however, includes numerous 
harvesting ant species found in mesic habitats (W. L. Brown, Jr., 
pers. comm.). On the other hand, species of the tropical Asian genus 
Pheidologeton have been considered harvesting ants, but while 
these ants harvest large quantities of seeds, apparently none store 
seeds (pers. obs.). 
The majors of all Acanthomyrmex species have traits characteris- 
tic of seed millers, including greatly enlarged heads and heavy 
mandibles with the masticatory borders often severely worn. It is 
therefore reasonable to infer that the diet of all these species consists 
at least in part of seeds, but whether all are harvester ants remains 
to be ascertained. 
Behavior of the majors. In the course of this study various roles 
have been implicated for majors of A. notabilis : 
(1) Majors presumably mill seeds. 
(2) Majors play an important role in colony defense, guarding 
the entrance when there is a disturbance there, and often 
biting intruders that attempt to enter the nest. 
(3) Majors sometimes carried immatures following severe nest 
disturbances that led to worker dispersal with brood. 
(4) Majors occasionally held or carried immatures in an quies- 
cent colony. 
(5) I have one observation of a major holding and carrying a 
piece of prey. 
As in other Acanthomyrmex species, the gaster of A. notabilis is 
small, contracted and beadlike; there is apparently no tendancy for 
majors to take on a replete condition. 
