Insects and the Cold

Insects and the Cold

Ken Johnson

With the recent cold snap many people have been wondering about how it’s going to affect the insect populations. For the most part, insects will survive just fine (depending on your point of view, this could be good or bad). Insects use a variety of strategies to survive through the winter.

The first strategy some insects will use is to avoid the cold. 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. An example of this would be monarchs. 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 leaf hoppers, survive in Southern states and will migrate north as temperatures begin to warm.

For those insects that stick around, 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 creating proteins to control the way in which they freeze to minimize damage to their cells (these insects are called freeze tolerant).

The final strategy insects use to survive the winter is to avoid freezing by producing chemicals in their bodies (freeze avoidance). Most insects that overwinter in cold environments in the Northern Hemisphere use this approach. As temperatures begin to cool, these insects will start creating anti-freeze chemicals. These chemicals will allow the insects bodies’ to supercool (reach temperatures below freezing, 32ᵒF). Therefore, the insects won’t freeze until they reach their super-cooling point. Some insects that take this approach include Japanese beetles (super-cooling point is 19ᵒF), emerald ash borer (super-cooling point is -26ᵒF), and codling moth (super-cooling point is -10ᵒF).

Many insects will also seek shelter during the winter to help them avoid cold temperatures. For example, white grubs 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. In addition to protection from cold weather, these sheltered locations can also help regulate the temperatures so they aren’t exposed to the large temperature fluctuations we sometimes experience during the winter.

While the cold temperatures we have had may have gotten an insect here or there, come Spring it should be business as usual.

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