Comparison of polygyne and monogyne red imported fire ant (Hymenoptera: Formicidae) population densities

Polygyne or multiple-queen colonies of red imported fire ant, Solenopsis invicta Buren, are reported to be a substantially greater environmental and economic problem than monogyne or single-queen fire ants because of much higher population densities associated with polygyny. This study compared population densities of polygyne and monogyne fire ant colonies using measures of mound density, worker number ant biomass, metabolic consumption, and standing caloric energy of ant biomass. We began the experiment by counting and measuring mounds at 14 polygyne and 14 monogyne sites located within a 35-km radius of Gainesville,, FL. Average mound densities were 3.03 times larger at polygyne sites than at monogyne sites (470 versus 155 mounds per hectare). To adjust for differences in mound size, 22 monogyne and 21 polygyne mounds of various sizes were excavated from 16 of the experimental sites. Colony size and biomass were regressed on mound volume. These regressions then were used to estimate colony size and colony biomass from the mound volumes measured at the 28 field sites. The estimated colony sizes and colony biomasses at each site were summed and used to estimate field population densities. Polygyne populations contained 1.94 times more workers per unit area (35 million versus 18 million workers per hectare) and 1.86 times more biomass (27.7 versus 14.9 kg wet weight per hectare) than monogyne populations. Energy usage and standing energy of the ants per hectare were, respectively, 2.30 and 1.90 times higher in polygyne populations. Overall, this study indicates that polygyne population densities are approximate to 2 times larger on average than monogyne population densities.