Where Do Insects Go in Winter?

Winter Survival Strategies for Insects

Convergent lady beetles stay warm in clusters. Photo: © Scott Bauer, USDA Agricultural Research Service, Bugwood.org

An insect doesn’t have the benefit of body fat, like bears and groundhogs, to survive freezing temperatures and keep internal fluids from turning to ice. Like all ectotherms, insects need a way to cope with fluctuating temperatures in their environment. But do insects hibernate? 

In a very general sense, hibernation refers to the state in which animals pass the winter. Hibernation suggests the animal is in a dormant state, with its metabolism slowed and reproduction paused.

Insects don't necessarily hibernate the way warm-blooded animals do. But because the availability of host plants and food sources are limited during the winter in cold regions, insects do suspend their usual activities and enter a dormant state.

So how do insects survive the cold winter months? Different insects use different strategies to avoid freezing to death when the temperature falls. Some insects employ a combination of strategies to survive the winter.

Migration

When it gets cold, leave!

Some insects head to warmer climes, or at least better conditions, when winter weather approaches. The most famous migrating insect is the monarch butterfly. Monarchs in the eastern U.S. and Canada fly up to 2,000 miles to spend their winter in Mexico. Many other butterflies and moths also migrate seasonally, including the gulf fritillary, the painted lady, the black cutworm, and fall armyworm. Common green darners, dragonflies that inhabit ponds and lakes as far north as Canada, migrate as well.

Communal Living

When it gets cold, huddle up!

There’s warmth in numbers for some insects. Honey bees cluster together as the temperatures drop, and use their collective body heat to keep themselves and the brood warm. Ants and termites head below the frost line, where their large numbers and stored food keep them comfortable until spring arrives.

Several insects are known for their cool weather aggregations. Convergent lady beetles, for example, gather en masse on rocks or branches during spells of cold weather. 

Indoor Living

When it gets cold, move inside!

Much to the displeasure of homeowners, some insects seek shelter in the warmth of human dwellings when winter approaches. Each fall, people's houses are invaded by box elder bugs, Asian multicolored lady beetles, brown marmorated stink bugs, and others. While these insects rarely cause damage indoors – they're just looking for a cozy place to wait out the winter – they may release foul-smelling substances when threatened by a homeowner trying to evict them.

Torpor

When it gets cold, stay still!

Certain insects, particularly ones that live in higher altitudes or near the Earth’s poles, use a state of torpor to survive drops in temperature. Torpor is a temporary state of suspension or sleep, during which the insect is completely immobile. The New Zealand weta, for example, is a flightless cricket that lives in high altitudes. When temperatures drop in the evening, the cricket freezes solid. As daylight warms the weta, it comes out of the torpid state and resumes activity.

Diapause

When it gets cold, rest!

Unlike torpor, diapause is a long-term state of suspension. Diapause synchronizes the insect’s life cycle with seasonal changes in its environment, including winter conditions. Put simply, if it’s too cold to fly and there’s nothing to eat, you might as well take a break (or pause). Insect diapause may occur in any stage of development:

  • Eggs – Praying mantids survive the winter as eggs, which emerge in spring.
  • Larvae – Woolly bear caterpillars curl up in thick layers of leaf litter for winter. In spring, they spin their cocoons.
  • Pupa – Black swallowtails spend winter as chrysalids, emerging as butterflies when warm weather returns.
  • Adults – Mourning cloak butterflies hibernate as adults for the winter, tucking themselves behind loose bark or in tree cavities.

Antifreeze

When it gets cold, lower your freezing point!

Many insects prepare for the cold by making their own antifreeze. During the fall, insects produce glycerol, which increases in the hemolymph. Glycerol gives the insect body “supercooling” ability, allowing body fluids to drop below freezing points without causing ice damage. Glycerol also lowers the freezing point, making insects more cold-tolerant, and protects tissues and cells from damage during icy conditions in the environment. In spring, glycerol levels drop again.

 

 

1 Definition from "Hibernation," by Richard E. Lee, Jr., Miami University of Ohio. Encyclopedia of Insects, 2nd edition, edited by Vincent H. Resh and Ring T. Carde.