Native and exotic ants (Hymenoptera: Formicidae) of Georgia
Ipser, Reid Matthew
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The red imported fire ant, Solenopsis invicta Buren, is an invasive species that causes medical and economic problems, endangers domestic animals and wildlife, displaces native species, and disrupts natural habitats. This pest ant species now occupies much of the southeastern U.S., parts of the southwestern U.S., and has invaded southern California. This study was undertaken to define selected ecological relationships and competitive interactions of this invasive ant to serve as a basis for development of biologically-based management strategies. Red imported fire ant occurrence, activity, and interactions with native ant species were compared in canopied and uncanopied habitats at two central Georgia locations. Fire ant density and activity were significantly greater in open than in canopied habitats. Native ant species were numerous and competed with fire ants via predation of reproductive alates and foraging for food resources in the canopied habitats. A statewide survey for ground-dwelling ants expanded the list of taxa occurring in the state to 144. Of these, three are undescribed species belonging to two genera, Myrmica and Stenamma. Native species that compete with S. invicta were collected from the majority of the sites surveyed, thus, indicating the potential for competitive interaction with S. invicta. Laboratory choice assays determined the bait particle size preference of S. invicta, the Argentine ant (Linepithema humile (Mayr)), and four native ant species. Particle size preference was positively correlated with worker ant head capsule width with large particles being preferred by those species with wide head capsules. Results indicate that particle size preferred by S. invicta overlap those of Aphaenogaster fulva Roger, A. lamellidens Mayr, and Formica pallidefulva Latreille. Pheidole dentata Mayr preferred a small particle size. Competitive interactions between S. invicta and the four native species for bait particles resulted in dominance of the laboratory foraging arena by S. invicta. Field testing at Griffin, Georgia further determined that single broadcast applications of hydramethylnon bait and fipronil granules at recommended rates in early summer reduced fire ant mound density and fire ant worker activity in treated areas. The effects of fipronil were longer-lasting that those of hydramethylnon. Neither hydramethylnon nor fipronil reduced populations of native ant or other ground-dwelling arthropod species in this study.