Date of this Version
Southwestern Naturalist (May 21, 1982) 27(2): 245-246.
Colonies of Pogonomyrmex occidentalis Cresson (Hymenoptera: Formicidae) may live an average of 22 to 43 years. The population dynamics of individual colonies of P. occidentalis adjacent to the Univ. Nebraska's Cedar Point Biol. Sta., Keith Co., Nebraska, is the subject of an ongoing investigation. The habitat is a moderately grazed shortgrass prairie dominated by Bouteloua hirsuta, B. gracilis, and Buchloe dactyloides, with Stipa comata, Aristida spp., and various forbs. The colonies studied are in a triangular area about 400 m long and 100 m across at the widest point. The area appears to be at carrying capacity for P. occidentalis colonies: distances between colonies are not large and are quite uniform (̅X = 14.5 m, SE = 0.8 m for 48 colonies, E. Routman, unpubl.)
In July 1981, there were 75 marked colonies in the study area, 57 of which had been followed since August 1977. Of the original 57 colonies, 52 were still alive. One colony died in each of 1978, 1979, and 1981, two in 1980. This is an average death rate of 0.023 colonies per year.