How do insects survive cold weather?

JACKSONVILLE, Ill. — Winter can be harsh, especially with the arrival of snow and sub-zero temperatures. While we often retreat indoors or add a few more layers to avoid cold temperatures, many other critters, like insects, must tough it out outdoors. Insects have developed a variety of strategies to deal with the arrival of cold temperatures.

Leave the cold behind

Some insects that we find in Illinois won’t survive our freezing winter temperatures. So, instead of trying to make it through the winter here, they’ll survive elsewhere. The most well-known example of this is monarch butterflies. As we approach fall, monarchs will begin to migrate south and will eventually reach Mexico, where they will overwinter. As temperatures begin to warm again come spring, they will begin migrating north, and their children or grandchildren will arrive in Illinois.

Others, like armyworms and potato leafhoppers, won’t migrate south (they die in northern parts of the country) but will survive in southern states and will move north as temperatures begin to warm.

Stick around and tough it out

Many insects are year-round residents in Illinois and, depending on the species, may overwinter as eggs, nymphs or larvae, pupae or adults. For many of these insects, low temperatures aren’t necessarily the problem; the formation of ice crystals in their bodies is.

If ice crystals rapidly form in their bodies, their cells will burst, resulting in damage and likely death. Some insects, like woolly bear caterpillars, will avoid this by using chemicals to control the way in which and where they freeze and, therefore, minimize damage to their cells.

The other strategy insects that stick around for the winter use to survive is to produce chemicals in their bodies to avoid freezing altogether. As temperatures begin to cool, these insects will start creating anti-freeze chemicals. These chemicals allow the insect’s bodies to supercool (reach temperatures below freezing, 32ᵒF). Therefore, the insects won’t freeze until they reach their supercooling point. Some insects that take this approach include Japanese beetles (supercooling point is 19ᵒF), emerald ash borers (supercooling point is -13ᵒF), and codling moths (supercooling point is -10ᵒF).

Finding shelter

While air temperatures can get cold enough to kill insects, most insects will overwinter in protected areas where temperatures do not get nearly as cold. For example, white grubs (like Japanese beetles) in the soil will not be exposed to extremely cold temperatures because the soil will insulate them. Others will seek shelter under leaf litter, under bark, or even in your home. All of these will provide some protection from cold temperatures.

Snow is also an excellent insulator and offers another layer of protection. Several inches of snow can potentially keep the ground temperatures dozens of degrees warmer than the air temperature. Snow also helps protect from large temperature fluctuations in the soil, which can be detrimental to insects as well as plants.