Nesting and food resources of syntopic species of the ant genus Polyrhachis (hymenoptera, formicidae) in West-Malaysia

Polyrhachis is one of the largest ant genera in the world distributed in the Old World tropics and subtropics. We investigated the nesting and nutrition habits of 10 syntopic species of Polyrhachis in West-Malaysia. Striking differences between these species exist in regard to the nesting habits. Our research revealed four different nest types (soil nests, nests in preformed cavities, nests constructed of dead vegetative and soil particles, silk nests). The utilization of silk for nest construction expands the nest diversity of Polyrhachis considerably (nests in preformed cavities with silk supplement, pure silk nests, silk nests reinforced by dead vegetative and soil particles). In regard to nutrition habits of Polyrhachis two major modes were found: The tending of trophobionts and the opportunistic exploitation of sugary resources. The trophobiotic species keep their trophobionts inside the nest, inside pavilions, openly exposed and guarded or not guarded by the workers. Species of this group are characterized by large colonies and highly efficient recruitment systems. They defend food sites and sometimes establish territories. The non-trophobiotic species have small colonies, mostly less efficient recruitment systems and do not establish territories or defend food sites. Thus in the genus Polyrhachis nesting habits as well as nutrition habits seem to be key factors allowing the coexistence of so many different species.