How does Antarctica’s only native insect species survive extreme winter?

Flightless Antarctic midge (Belgica antarctica) is the only known insect native to Antarctica that is able to survive the extreme climate. Researchers have uncovered a part of the mystery of how the Antarctic midge copes with freezing temperatures. They found that the midge deals with the seasons during its two-year life cycle by undergoing quiescence in its first year and obligate diapause in its second. Quiescence is a form of dormancy in immediate response to adverse conditions, and when conditions improve, the organism becomes active again. Quiescence enables a swift transition between active and inactive lifestyles, making it possible to maximally exploit periods when temperatures exceed a certain threshold. Obligate diapause is a dormant period naturally induced at a fixed time in an organism’s life cycle, a rare form seen in insects in temperate regions. This occurs in anticipation of an upcoming harsh environment, allowing insects to accumulate additional energy reserves and seek suitable overwintering sites before diapause entry. The Antarctic midge larvae usually grow to their second instar by the first winter and undergo quiescence so that they can quickly resume development at any moment when it suddenly becomes warmer. Under summer-like conditions, larvae could develop from egg to the fourth-instar larval stage without interruption. As the second winter approaches, the larvae in the final fourth instar do not pupate. Instead, they enter obligate diapause so that they all emerge as adults when summer arrives. As adults, they have only a few days of life and need to find a mate, so this timing mechanism is key to their survival. “Diapause and quiescence ensure developmental and reproductive success in this extremophile insect,” the authors write.