Seasonal activity and bait preferences of the Argentine ant (Hymenoptera: Formicidae).

Abstract

Foraging by workers of Argentine ants, Linepithema humile (Mayr), in California was seasonal, with peak activity occurring from June to October. Workers foraged throughout the other cooler months, albeit at a much reduced level. The number of foragers was directly associated with early morning and late afternoon temperature. As temperature at 1600 hours increased, the number of foragers increased. Sucrose and honey water and solid foods containing insect protein were the most preferred food throughout the year. During the summer months, 26 to 60% (wt.) of the food foraged by workers was protein whereas this dropped to 16 to 40% during the winter. When given a choice between carbohydrates and protein bait-bases throughout the study, L. humile foraged considerably more carbohydrate. Presuming that foraging choice reflects the nutritional needs within the colony, these data suggest colony requirements for protein may be greater than initially suspected. Optimal baiting programs might include protein baits in the early summer and liquid sucrose baits in summer and early fall.