Occurrence and Species Diversity of Ground-Dwelling Worker Ants (Family: Formicidae) in Selected Lands in the Dry Zone of Sri Lanka

Abstract

Ants are an essential biotic component in terrestrial ecosystems in Sri Lanka. Worker ants were surveyed in six forests, uncultivated lands and, vegetable and fruit fields in two Districts of the dry zone, Anuradhapura and Polonnaruwa, from November, 2007 to October, 2008 by employing several sampling methods simultaneously along five, 100 m transects. Soil sifting, litter sifting, honey-baiting and hand collection were carried out at 5 m intervals along each transect. Twenty pitfall traps were set up throughout each site and collected after five hours. Air and soil temperatures, soil pH and soil moisture at each transect were also recorded. Use of several sampling methods yielded a higher value for species richness than just one or two methods; values for each land ranged from 19 – 43 species. Each land had its own ant community and members of Amblyoponinae, Cerapachyinae, Dorylinae, Leptanillinae and Pseudomyrmecinae were recorded for the first time from the dry zone. Previous records of 40 species belonging to 23 genera in 5 subfamilies for the Anuradhapura District are updated to 78 species belonging to 36 genera in 6 subfamilies. Seventy species belonging to thirty one genera in 9 subfamilies recorded from the first survey of ants in Polonnaruwa lands can be considered a preliminary inventory of the District; current findings updated the ant species recorded from the dry zone to 92 of 42 genera in 10 subfamilies. Consequent to this sum, the estimate of ant diversity of Sri Lanka rises to 202 species in 64 genera while 12 subfamilies remain unchanged.