Supercooling in a freeze-tolerant cranefly larva, Tipula sp.

The freezing curves of individuals of Tipula sp. revealed two markedly separate freezing events during winter. The initial freezing event occurred at about −3°C, the second at about −5°C. Larvae survived freezing to −10°C and contained about 30% unfreezable water. Larvae ligated close to the anus supercooled to −5°C, yet did not survive freezing. The drop in relative water content from about 76–81% gave rise to a somewhat smaller depression of haemolymph melting point than what should be expected from the water loss. Thus, the data indicated that osmolytes must have been removed rather than added to the body fluid of hibernating larvae.