Aquatic Insects of Modi Khola River in PARBAT, Nepal

Abstract

Aquatic insects are those insects that spend some part of their lifecycle closely associated with water, either living beneath the surface or skimming along on top of the water and they are abundant in most freshwater habitat. In aquatic ecosystem they play vital role or used as indicator of water. In this study, aquatic insects were collected from nine sampling sites of river across different habitats (near to forest area, near to agricultural field and near to human settle area). Each sampling site further divided into three sampling points on the basis of river heterogeneity. Insect collection was done by Sweeping method for littorial zone and D-Frame kick net for benthic zone by One minute kick method, Sieving was used for sandy places of rivers and All out search method was used in all possible substrata. The relation of aquatic insects with physical parameters was showed by using Karl Pearson’s Correlation method. A total of 2,230 insects belonging to 48 genera under 33 families and eight orders including of two unidentified species were recorded. During the study period the highest abundance of insect species was from order Ephemeroptera of the total insects sampled. It was followed by Trichoprera, Diptera, Plecoptera, Odonata, Megaloptera, Coleoptera and Hemiptera. Seasonally, abundance of orders of insect was highly varied. The diversity index and species richness of the insects were recorded higher in the pre monsoon in comparison to post monsoon. Analysis of variance shows no significant relation between aquatic insects and seasons. Near to forest area, diversity of insects was high followed by near to agricultural field and human settle area. The number of aquatic insects shows positive relation with DO but negative relation with temperature, velocity and CO 2 in both seasons. In pre monsoon, diversity shows positive correlation with alkalinity and negative with pH.