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They don’t let the cold bug them: insect strategies to survive winter in Minnesota

We cope with cold Minnesota winters in various ways. Some of us avoid the cold by moving south for the winter, some of us grit our teeth during frigid days and then retreat inside with warm beverages and blankets. Some face the cold in shorts and no jacket and claim that they love the freezing cold weather. Insect strategies for surviving Minnesota winters are shockingly similar to our human strategies. Some insects find different ways to avoid the cold—perhaps they migrate or find overwintering habitat; others face the cold but utilize methods to keep themselves from freezing. Still others allow themselves to freeze.

The avoidance strategy is common among insects. Many insects find shelter over the winter months, sometimes in large groups or aggregations with insects of the same species. Most species that find shelter go into diapause, which is the insect version of hibernation. Their metabolism slows down, and they go into a sleep-like state. Tent caterpillars endure diapause as egg masses on branches. Turf-feeding grubs (like June beetles and Japanese beetles) overwinter deep in the soil as larvae, as do European corn borers. Cecropia moths and swallowtail butterflies overwinter as pupae in cocoons or chrysalis. Bean leaf beetles spend the winter as adults under loose tree bark or in fallen leaves.

Others avoid the cold by winging it down south. Insects which migrate from Minnesota to warmer climates include monarch butterflies, painted lady butterflies, and common green darner dragonflies. Common species that aggregate include honey bees, which stay warm in hives, native lady beetles, which overwinter in groups under bark or firewood, and Multicolored Asian lady beetles which find shelter in our homes.

Some insects prevent their bodies from freezing to survive the winter. Several species can supercool their bodies by making chemicals, similar to antifreeze, which prevent ice from forming within their bodies. Codling moths, emerald ash borers, gypsy moths, and soybean aphids supercool. Soybean aphids, in egg form, cool themselves to withstand temperatures down to -29°F!

Instead of preventing themselves from freezing, some insects have adapted to survive freezing. Their physiologies allow their bodies to freeze but not be damaged. They survive by using specialized proteins which regulate the way they freeze to prevent cell damage. Body fluids that circulate outside these insects’ cells freeze, forcing water out of the cells, which lowers the freezing point, and protects the cells themselves. Goldenrod gall flies and wooly bear caterpillars utilize this freezing strategy.

You may notice that there are some important insects not mentioned as using any of these strategies. Well, some insects don’t survive Minnesotan winters. Whiteflies, striped cucumber beetles, and corn earworms die as temperatures drop and then migrate from the south or from greenhouses in the spring. Despite individuals dying, insects generally find a way to keep their populations going.

Insects adapt. They evolve rapidly and can cope with changing conditions, making several insect species even more adept at coping with Minnesota winters than the hardiest Minnesotan human.