How to study subterranean army ants: a novel method for locating and monitoring field populations of the South East Asian army ant Dorylus (Dichthadia) laevigatus Smith, 1857 (Formicidae, Dorylinae) with observations on their ecology

Summary:

A new method employing palm oil as bait was developed for studying the distribution and ecology of subterranean army ants. In SE Asia the hypogaeic army ant Dorylus laevigatus was found to be very common in both forested and open environments. More than 10000 workers were found at individual baits. The workers cooperatively dig a three-dimensional tunnel network into the soil. Over a period of 72 days no emigrations of D. laevigatus could be detected, a first indication of a facultatively stationary way of life in this ant. Encounters with Pheidologeton silenus about food resources were observed. In feeding experiments D. laevigatus readily took a variety of arthropods and annelids but ignored starch containing vegetables as food. The rare hypogaeic D. (Alaopone) cf. vishnui could be collected for the first time in India and Sri Lanka. Also the epigaeic D. (Anomma) nigricans from Africa were found to be attracted to palm oil. The oil-method thus provides the opportunity to detect and monitor populations of army ants of the genus Dorylus in tropical and subtropical habitats.