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Psyche 
[Vol. 89 
response. Subsequently, crushes of the head, thorax, and gaster 
were offered on applicator stick tips at the nest entrance. Also, 
crushes of dissected poison and pygidial glands (Holldobler and 
Engel, 1979) were offered. Only head crushes produced attraction. 
Whelden’s (1958) studies, in addition to our own histological investi- 
gations, revealed a group of large glandular cells at the base of the 
mandible. The indirect evidence described above suggests that dur- 
ing prey capture the contents of these cells are released, attracting 
workers in the vicinity to assist in subduing prey. 
3. Ecology and social evolution 
The results of this study and previous investigations suggest that 
populations of A. pallipes are unicolonial. Workers from different 
subnests within a population show no aggression toward each other. 
Such worker compatibility has been demonstrated in Rhytidopon- 
era metallica (Haskins and Haskins, 1979), whose populations 
appear to be structurally similar to those of A. pallipes, but occupy 
larger area geographically. Workers taken from nests three miles 
apart were not mutually hostile. The lack of aggression was consist- 
ent within, but not between populations. Ambylopone pallipes col- 
onies appear to be similarly viscous, but do not occupy as extensive 
an area. 
Observations in the laboratory are in accord with Brown’s (1960) 
position which states that after mating, females “always or usually 
return to the parent nest”. Secondary polygyny in this species, in 
addition to its patchy distribution, indicates that this species is in the 
terminology of Holldobler and Wilson (1977) a habitat specialist. 
The characteristic A. pallipes habitat is cool, damp, heavily shaded 
woodland. Nest site and prey abundance are also important fea- 
tures. Populations apparently grow slowly, and through reproduc- 
tion by budding, eventually saturate the habitat. Such a scheme 
does not rule out the occurrence of dispersal flights, which have 
been witnessed on occasion (Haskins, 1928). As colonies become 
more populous within a habitat, dispersal flights should occur more 
frequently in order to colonize additional areas. Once a founding 
queen locates a preferred habitat, colony reproduction again is 
accomplished through budding. The strategy may be similar to that 
of the mound building species Formica exsectoides. However, it 
must be noted that in laboratory situations, A. pallipes queens have 
never been observed to successfully found colonies (Haskins, per- 
