Specific initial responses of Solenopsis geminata (Hymenoptera: Formicidae) to selected herbivore prey in field crop environments

Abstract The importance of generalist predators to biological control in agroecosystems is widely recognized. However, specific behavioral responses of predators when finding prey in the field are sometimes unknown. We investigated initial predatory responses (i.e. recruitment, attack, retrieval) of foraging workers of the tropical fire ant, Solenopsis geminata F. (Hymenoptera: Formicidae) against important agricultural pests and one beneficial parasitoid under crop field conditions on soil. Additionally, widely available, non-crop pest insects: mealworms ( Tenebrio molitor L., Coleoptera: Tenebrionidae) and Indianmeal moth Plodia interpunctella Hübner (Lepidoptera: Pyralidae) eggs were tested as prey. For some prey items, we examined the influence of an adjacent food source (hot dog slice) upon ants. Fire ants immediately retrieved Bagrada hilaris Burmeister (Hemiptera: Pentatomidae) eggs. Ants did not attack but immediately tended the myrmecophilic aphid, Aphis coreopsidis (Thomas) (Hemiptera: Aphididae) with or without adjacent food source. Less than 10 % of eggs of diamondback moth Plutella xylostella L. (Lepidoptera: Plutellidae) and Plodia interpunctella were retrieved, perhaps due to small size and little energetic/nutritional value. Plutella xylostella pupae with and without cocoons were retrieved; ants extracted pupae from cocoons in situ and then introduced the pupae to the ant colony. Ants did not retrieve pupae (with or without cocoons) of the diamondback moth parasitoid, Diadegma insulare (Cresson) (Hymenoptera: Ichneumonidae), suggesting repellence mechanisms. The presence of alternate food source did not affect retrieval of eggs nor of T. molitor larvae. This information clarifies putative ecosystem services of S. geminata that are relevant for integrated pest management decisions in this region.