Food habits of Aenictus army ants and their effects on the ant community in a rain forest of Borneo

In a rain forest at the foot of Mt. Kinabalu, Borneo, we observed the food habits of Aenictus laeviceps and A. gracilis and surveyed the effects of A. laeviceps on the general ant community. We collected totals of 2,360 and 6 ,268 prey units, respectively, from seven A. laeviceps and six A. gracilis colonies; ants constituted 99.9% of all prey units. Dominant prey genera we re Camponotus (48.2% in wet weight), Pseudolasius (20.8%), and Polyrhachis (15.2%) in A. laeviceps and Technomymex (52.1%), Paratrechina (22.4%), and Crematogaster (11.9%) in A. gracilis. A. laeviceps primarily hunted larger ground ants with small- or medium-sized colonies; in contrast, A. gracilis frequently foraged on smaller arboreal ants with larger colonies. Of the to tal wet weight of prey ants, brood constituted 88.7% in A. laeviceps and on ly 68.7% in A. gracilis. This was probably because workers of A. gracilis w ere quicker in behavior and hunted adult workers more frequently than A. la eviceps. While 98.5% of the prey units were transported by single workers o f A. gracilis, 71.5% were carried by up to 20 A. laeviceps workers. The num bers of ant colonies and species were significantly smaller in laeviceps-ra ided quadrats than in controls. This was mostly due to the escape of ants t hat nested under litter and had relatively larger colonies. Large colonies usually influence the foundation and establishment of incipient small colon ies.