The Influence of Habitat Structure and Physico-Chemical Variables on Entomofaunal Diversity in a Headwater Stream of Pamba River, Kerala

The present investigation was conducted to determine the effect of stream habitat structure and physico-chemical variables on the diversity of insect community from a headwater stream of the holy river Pamba in the Western Ghats. Assessment of habitat variables, analysis of Physico-chemical parameters, and collection of both aquatic and riparian insects from the respective stream stretch were carried out from January to December 2019 on monthly basis. A total of 25 species of insects belonging to six orders, 14 families, and 20 genera were reported from the headwater stream in the Western Ghats. Deep pools, boulder undercuts, overhangs, aquatic macrophytes, and leaf litter formed the habitat features available to the aquatic communities. The substrate composition and stability affected the positioning, movement, and feeding activities of the insect communities in the stream channel. The pH of the stream water was recorded at 6.02±0.21, 6.65±0.05, 6.47±0.4 during summer, monsoon, and winter respectively, which is optimal for the growth of the insect community. The summer is noted with an increased air temperature of 34.9±1.34oC and showed high Lepidopteran abundance. The highest Dissolved Oxygen (DO) content in the stream water was recorded during the Monsoon period (9.2±1.54 mg/L). The healthy stream supported a rich insect community, which showed population fluctuation on a seasonal basis. The stream habitat with its rich riparian buffer contributes to the breeding and feeding sites of the entomofauna; also supports many endemic and migrant Lepidopterans.