Impact of the Red Imported Fire Ant (Hymenoptera: Formicidae) on Epigeic Arthropods of Cotton Agroecosystems

The red imported fire ant, Solenopsis invicta Buren (Hymenoptera: Formicidae), has been studied extensively in its role in aboveground food webs of agroecosystems of the southern United States. There is also a limited body of evidence suggesting that S. invicta may significantly influence the soil fauna. This study examined the influence of fire ants on the arthropod communities at the soil surface of cotton, Gossypium hirsutum L., fields at two field sites operated by the University of Georgia in Athens and Tifton, GA (1 yr at each location). Fire ant abundance was suppressed in large plots with ant-specific hydramethylnon-based bait, and arthropods were collected from treatment and control plots by using pitfall traps during multiple week-long sample periods to measure the abundance of epigeic arthropods. Sampling was conducted from June through September 2006 in Athens and from July through September 2007 in Tifton. Although fire ant suppression decreased the abundance of erythraeid mites and nitidulid beetles at both sites, the majority of effects were site-specific. Other taxa positively associated with fire ants included oribatid mites and gnaphosid and linyphiid spiders. In contrast, the abundance of springtails, earwigs, endomychid beetles, and thrips increased with fire ant suppression. This study demonstrates that S. invicta can significantly influence both pest and beneficial epigeic arthropods and that although fire ants exert clear effects on specific taxa, their effects are not uniform within a given trophic group as members from the same guild were differentially impacted.