Ecology and Life History of the Rhytidoponera Impressa Group (Hymenoptera: Formicidae) I. Habitats, Nest Sites, and Foraging Behavior

The ponerine ants of the genus Rhytidoponera constitute a rich assemblage of species, widespread throughout Australia, with lesser representation in Melanesia and adjacent regions (Brown, 1958; Wilson, 1958). On the Australian mainland they have collectively occupied a broad range of habitats, and often rank among the more abundant members of an ant community. Considerable interest centers on the unusual habit, apparently widespread in the genus, of reproduction by mated "workers" in lieu of a morphologically differentiated dealate queen (Brown, 1953, 1954; Whelden, 1957, 1960; Haskins & Whelden, 1965). The Rhytidoponera impressa group consists of a small, distinctive cluster of species occurring in mesic habitats (mostly rainforest and wet sclerophyll) along the east coast of Australia and in New Guinea. Until recently, the impressa group was thought to comprise no more than three species, all reproducing by means of distinct winged queens (Brown, 1953, 1954; Haskins & Whelden, 1965). However, recent studies of systematic relationships and colony structure in the impressa group have revealed the presence of at least 5 closely related species and the occurrence of reproduction by both queens and mated workers (Ward, 1978, 1980). There is a notable paucity of detailed ecological studies on rainforest ponerines in general, and there have been no extensive field studies on Rhytidoponera. This paper summarizes information on habitat and nest site preferences, colony densities, and various aspects of foraging, in the impressa group. A second paper describes life cycle and reproductive patterns (Ward, 1981).