1986] 
Moffett — Oligomyrmex overbecki 
115 
extent in brood care. It is possible that the repertoire of majors is 
normally more restricted, but that high minor worker mortality in 
the captive colony and the resulting altered caste ratios led to an 
expansion of the major worker repertoire. The relationship between 
worker caste ratios and major repertoires for dimorphic ants is only 
beginning to be explored (see Wilson 1984, 1986). 
Observations on a Oligomyrmex cf. solidaris colony collected in a 
rotten log from Bako National Park in Sarawak indicates that the 
majors of this species also are semi-replete and are crucial to colony 
defense. O. cf. sodalis majors were quick to attack Pheidologeton 
silenus and Pheidole megacephala workers dropped into the nest 
areas, and were much more efficient than minor workers in inflict- 
ing damage on the enemy. The importance of rapid and effective 
response to workers of these ant species was dramatized when the 
artificial nest container housing the O. cf. sodalis colony was raided 
by Pheidole megacephala ants. Within a four hour period the Phei- 
dole had completely destroyed the Oligomyrmex colony of several 
hundred individuals and emigrated into their nest container. 
Minor workers of O. overbecki show a pattern of temporal poly- 
ethism common for ants (Wilson, 1971), caring for immatures (par- 
ticularly smaller immatures) as callows and shifting towards 
foraging activities as they age. Probably only younger workers are 
semi-repletes, with the ants losing their replete condition at about 
the time they begin to forage. 
Oligomyrmex overbecki (as well as O. cf. sodalis, pers. obser.) 
forms trunk trail foraging routes, as do a variety of other pheido- 
logetine ants: Erebomyrma nevermanni (Wilson, 1986); Pheidolo- 
geton diversus (Moffett, 1984) and all other Pheidologeton species 
(pers. obser.); and Lophomyrmex bedoti (Moffett, 1986). 
Acknowledgements 
I thank E. O. Wilson and D. H. Murphy for encouragement and 
advice. The research was supported by grants from the National 
Geographic Society and Harvard University. 
Literature Cited 
Bhatkar, A. and W. H. Whitcomb. 
1970. Artificial diet for rearing various species of ants. Fla. Entomol. 53: 
229-232. 
