Natural History of the Workerless Inquiline Ant Pogonomyrmex Colei (Hymenoptera: Formicidae)

At least 10 workerless inquiline ant species are known from North America (Francoeur 1968, 1981; Wilson 1971, 1976; Talbot 1976; Buschinger 1979; DuBois 1981; Snelling 1981), most only from original collections. In this paper I present field and laboratory observations of Pogonomyrmex colei Snelling a new, apparently workerless, inquiline ant inhabiting a colony of Pogonomyrmex rugosus. P. colei appears to be a very rare species" extensive searching of the type locality for 4 yr has resulted in discovery of only a single colony. Nonetheless, observations on this colony provide insight into several important aspects of inquiline ant biology. P. colei is also of interest since it is the second apparently workerless congeneric inquiline inhabiting colonies of P. rugosus. Cole discovered the first inquiline species, Pogonomyrmex anergismus, near Silver City, New Mexico apparently prior to any major flight since he exposed "more than one hundred" inquiline reproductives upon opening the host nest (Cole 1954, 1968). Since host species mating flights occur soon after rain during mid to late summer (Htlldobler 1976; Rissing personal observation), it seemed reasonable to suspect P. anergismus responds to the same environmental cues for mating as does its host. Accordingly, in an effort to rediscover P. anergismus, I routinely checked most P. rugosus nests on a 25 ha study area in Boulder City, Nevada for flight activities and possible presence of inquilines during late summer 1978 and 1979 (study area described in Rissing 1981). P. colei was discovered during this effort.