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Insects are winter survivalists

Thursday, February 1, 2018

Q. How do insects survive the winter? Are they all eggs that have their own antifreeze?

Bill from Salem

A. Evolution has resulted in many creative ways to survive in temperate climates. Our resident insects are very well adapted to survive winter. This may be disheartening if you are thinking about Japanese beetles or brown marmorated stink bugs. In reality, very few insects are pests. In fact, many are beneficial, and we couldn’t live without them, or at least it would be a very different, very boring world.

In order to survive winter, insects enter diapause. The definition of diapause (and coincidently also the definition of an evening spent watching TV) is “an inactive state of arrested development.” The shorter daylight lengths of fall trigger this state. During diapause an insect’s metabolic rate drops to one-tenth or less, so it can use stored body fat to survive winter, and many insects produce alcohols for antifreeze. Their bodies can reach temperatures below freezing without forming cell-damaging ice.

Insects spend the winter in various life stages: egg, nymph, larvae, pupae or adult. Many do overwinter as eggs. Aphid eggs can be found in the bud scales of woody plants. Bagworms hang out as eggs inside this year’s bags. Tent caterpillars spend the winter as egg masses on branches.

Mourning cloak butterflies and bean leaf beetles spend the winter as adults in protected areas under loose tree bark and in fallen leaves. Native lady bugs overwinter in herds under fallen tree bark or firewood. Asian multicolored lady beetles look for a warm spot in our homes to wait for spring.

Yet other insects overwinter as larvae or immature stage. Turf feeding grubs overwinter deep in the soil as beetle larvae. European corn borers survive as full-grown larvae. Others such as cecropia moths and swallow tail butterflies overwinter as pupae in cocoons or chrysalis.

Diapause has to be terminated in order to return to activity, and the trigger is usually warm temperature. However, it would be a deadly mistake for an insect to “wake up” too soon. Therefore, most insects do not come out of diapause unless a long period of cold precedes the warm temperatures.

Insects are certainly adaptive, but winter conditions can affect their survival. Cold temperatures, fluctuations in temperatures, how long cold temperatures continue, how protected the overwintering location is, and if any snow cover is available all affect an insect’s survival. While we know a lot, we still have a lot to discover about how insects spend the winter.

Today’s answer by Sara Scudier, OSU Extension master gardener volunteer. Winter hours for the Plant and Pest Diagnostic Clinic vary. Submit questions to the clinic at 330-533-5538 or drop samples off to the extension office in Canfield.