Nine-Year Study of a Field Containing Both Monogyne and Polygyne Red Imported Fire Ants (Hymenoptera: Formicidae)

Abstract

Polygyne red imported fire ants, Solenopsis invicta Buren, are now pervasive in eastern Texas and are appearing with increasing frequency in other states. We therefore want to know whether a polygyne population replaces a monogyne one when both are present, and whether a polygyne population persists or is only an early developmental stage of a monogyne population. Between 1982 and 1991, we observed a 152.4 m (500 ft) transect containing both forms of the ant. After 9 yr, two distinct populations remained, although the monogyne population eventually had fewer mounds and occupied a smaller area. In 1982, there were 18 polygyne mounds within the first 30.5 m (100 ft) of the transect and 9 monogyne mounds in the last 91.4 m (300 ft). In 1991, the polygyne population contained 335 closely spaced mounds between 0 and 106.7 m (350 ft) of the transect; only three definitive monogyne mounds were found in the last 30.5 m (100 ft). There is no evidence that the polygyne population gradually differentiated into monogyne colonies. Seasonal size variability was evident in both populations.