It is not easy for insects to survive Iowa winters. Some literally can’t - they freeze to death (corn earworm, black cutworm) or migrate to warmer climates (potato leafhopper). Insects are unlike mammals and birds because they must generate their own heat (called ectotherms). Insects die when they are exposed to temperatures below the melting point of their body fluids, termed the lower lethal temperature. Over time, insects have developed several strategies to survive cold temperatures and none of them involve wearing fleece. Many insects have adapted to cold temperatures by entering diapause, which is like hibernation. Diapause is a developmental arrest to survive adverse seasons where individuals slow down metabolic activity.