Introduction

Abstract

Members of the family Chironomidae are true flies (order Diptera). They are the most widely distributed and frequently the most abundant insects in freshwater. Under certain conditions, such as at low levels of dissolved oxygen, larval chironomids may be the only insects present in benthic sediments. Extremes of temperature, pH, salinity, depth, current velocity, and productivity have been exploited by the immature stages of at least some chironomid species. Chironomids live in the glaciated areas of the highest mountains, including at elevations of up to 5600 m in the Himalaya (Kohshima, 1984; Sæther and Willassen, 1987) and are active at temperatures of −16 C. Larvae of Sergentia live at over 1000 m depth in the abyssal of the world's deepest body of freshwater, Lake Baikal (Linevich, 1963).