Foraging patterns in three sympatric forest ant species, <i>Prenolepis imparis, Paratrechina melanderi</i> and <i>Aphaenogaster rudis</i> (Hymenoptera: Formicidae)

Abstract. Ecological segregation was studied in Aphaenogaster rudis Emery, Paratrechina melanderi (Wheeler) and Prenolepis imparis (Say), the three commonest surface‐foraging ants in a Maryland (U.S.A.) hardwood forest community. P.imparis retreats from the surface during mid‐summer, but shows more cool‐season activity than do the other two species. P.melanderi is most active during the warmest months of the years. A.rudis is the most generalized of the three species in its seasonal activity pattern. P.imparis is a highly aggressive species which forms large mobilizations at rich food sources. P.melanderi is a timid species which forms small mobilizations. A.rudis is intermediate in both respects. Based on the results of baiting trials, P.imparis shows an apparent preference for protein‐fat food, P.melanderi prefers carbohydrate food, and A.rudis exhibits no significant preference for either fclod type. As a result of its extended seasonal activity, weak circadian periodicity, and lack of food specialization, A.rudis has the broadest annual niche of the three species studied. The unusual seasonal activity pattern of P.imparis results in a relatively low degree of annual niche overlap between this species and either of the other two. Overlap between A.rudis and P.melanderi is substantially higher. Experimental manipulations confirm that rates of resource removal by a behaviourally subordinate species (Amdis) are reduced in the presence of a dominant species (P.imparis). Persistence of these three widespread, abundant, relatively generalized ant species in local sympatry may in part reflect their differential success in: (a) finding food, (b) defending food, and (c) handling food items of different sizes.