Species richness, abundance and distribution of aquatic insects of Agusan marsh, Mindanao, Philippines

Abstract

A total of 59 species of aquatic insects was recorded from the major habitats in the flood-plain of Agusan Marsh. Species richness was greater in natural habitats than their respective adjoining ricefields, and did not differ among the natural habitats and between seasons. The water beetles had the highest species richness with 28 species, followed by aquatic and semi-aquatic bugs with 17 species, and dragonflies with 11 species, mostly libellulids. While most of the aquatic insects were fairly distributed in many habitats, several species appeared to be unique to one or two natural habitats. Water beetles were the most numerous insects in both wet and dry seasons. Aquatic insects were more abundant in the natural habitats than their adjacent ricefields; they were most abundant in Sedge-dominated Swamps. In ricefields, the site near the Fern-dominated Swamp had the highest abundance, while the site adjacent to the Bangkal Forest had the lowest.