Moist habitats are essential for adults of the Antarctic midge, Belgica antarctica (Diptera: Chironomidae), to avoid dehydration

Desiccation resistance of adult males and females of the midge, Belgica antarctica (Diptera: Chironomidae) was evaluated to determine how this short-lived stage maintains water balance in the dry Antarctic environment. Both sexes had slightly lower water content (approximate to 60%) and a higher dehydration tolerance (> 30% water loss) than most other insects. Water loss rates were high and increased rapidly at temperatures above 15 degrees C, indicating that the adult midges are more hygric than many other polar terrestrial arthropods. Water gain was accomplished by free water uptake with minimal or no contribution from absorption of water vapor or metabolic water production. Parameters related to water balance did not differ among populations from different islands. Overall, the high water requirements of the adult midge appear to be a significant challenge and presumably dictate that the adult midges must emerge during the brief period when free water is readily available and seek protected microhabitats that facilitate water retention.