Colony size and reproduction in the western harvester ant, Pogonomyrmex occidentalis

We report data from a four-year field study on the relationship between col ony size and reproduction in the western harvester ant, Pogonomyrmex occide ntalis. In all years, the likelihood of reproduction significantly increase d with increasing size in both field censuses during naturally-occurring ma ting flights and experimentally-watered colonies whose entire reproductive output was collected. However, the total amount of reproductive biomass was unrelated to colony size. We describe the size threshold for reproduction in P. occidentalis and show that it varies across years. Once colonies beco me reproductively mature, they reproduce consistently although not in every year. We describe a method for collecting the entire reproductive output f or desert ants whose reproductive flights are cued by rainfall.