This two-step process, called supercooling, allows body fluids to remain liquid at temperatures far below their normal freezing point. Supercooling is highly effective. Some insects have another strategy. They can isolate ice crystals between cells and allow them to form without danger of cell damage. The ability of insects to survive even the extreme conditions of a Yukon winter astonishes van Randen.
Most insects spend the winter in larval form.
Larvae seem to be better at producing glycerol, van Randen says, and therefore can survive through colder temperatures than adults. In cases where both larvae and adults survive, they often use different strategies, he says. The larvae of spruce bark beetles produce glycerol to protect their cells and spend the winter under the tree bark. However, the adults are less efficient at producing glycerol and need more protection. As soon as they reach maturity, they burrow out of the tree bark and drop to the bottom of the tree.