HOW DO SNOW FLIES REMAIN ACTIVE AT VERY COOL TEMPERATURES?
Many insects cannot survive near-freezing temperatures. Most of our body processes involve enzyme reactions (a type of chemistry) that work best within a range of temperatures. Snow flies therefore must have developed different enzyme systems that allow them to carry on the chemistry for body processes at cooler temperatures. Actual “freezing” poses a particularly difficult challenge. First, if tissues freeze solid, the fluid cellular and organ functions come to a halt–nothing can move. More disastrous is the fact that when ice crystals form, the sharp ice crystal points rupture cells and tissues and destroy the structure, as anyone who has frozen and thawed lettuce knows. Snow flies are cold hardy as adults for several reasons. Since adults probably do not eat solid food, food particles cannot provide the nucleus to start ice crystals growing. In addition, the electrolytes in the hemolymph (that is the chemicals in the clear “blood”) lower the natural freezing point (similar to how g
