Midge (Diptera: Chironomidae and Ceratopogonidae) emergence responses to temperature: experiments to assess midges’ capacity as paleotemperature indicators

Abstract

Chironomidae and Ceratopogonidae were tested experimentally for their responses to temperature. Three independent studies tested the effect of experimental temperatures (4, 14, and 24 °C) on emergence of midge faunas collected from littoral zones of three separate lakes, from profundal zones of three other lakes, and the littoral, sub-littoral and profundal zones of one lake. Results from these experiments indicate: that some taxa may achieve optimal development at cooler temperatures; that most taxa are cued for emergence by, and require, warmer temperatures; that exposure to temperatures too warm may result in developmental stress and sometimes death; that midge emergence events appeared more or less synchronous; and that emergences may be controlled by a threshold temperature as opposed to accumulation of degree-days. In these experiments, fauna collected from profundal zones exhibited high mortality rates when subjected to warm (24 °C) temperatures. In summation, some midge taxa may have relatively narrow optimal temperatures at which development and emergence can occur. Results from these experiments indicate that temperature directly impacts midges by regulating emergence and survival which may affect subfossil abundances and analyses typical with paleoreconstructions. Responses are similar to those predicted in paleoenvironmental inference modeling studies, and support the continued use of midges as paleotemperature indicators.