November 12, 2015

Insects and Winter​​​​​

What is the prognosis for insect survival this winter? First of all, insects have been on this earth longer than humans and have developed many mechanisms to adapt to and survive varying weather conditions. Regardless of winter conditions, insect numbers may be reduced but the insect species will not be eliminated.

Depending on the species, insects overwinter as eggs, larvae, or adults and each has its own method of surviving the winter (Figures 1 -3):

  • Eggs are usually deposited in protected areas and can survive extreme cold temperatures with little damage. Temperature and conditions at hatch are more important to survival than winter conditions.
  • Larvae also overwinter in protected areas in a form of diapause or suspended animation and can survive very cold conditions.​
  • Insects, which overwinter as adults, go into a stage similar to hibernation where the insect finds a protected area and sleeps through the winter.

So, what happens when there isn’t a protective snow blanket that gives the insect ideal survival conditions where the temperature stays uniform? Humans tend to like a winter with not much snowfall, moderate temperatures that warm above freezing, and maybe a few short cold spells. The winter we like might not be the favorite of the insect. Varying temperatures can cause the larval and adult insect forms to come out of their winter sleep, use energy without feeding, and not be prepared for a sudden temperature drop, which can cause it to become weak or die. Egg masses, which are more exposed to the changing elements, can dry out and die.

In summary, insects have adapted to most winter conditions, but the ideal condition for insect winter survival is a nice blanket of snow, regardless of the temperature. Open winters with varying temperatures and sudden cold spells after a warm spell can decrease survivability.

Figure 1. European corn borer overwinter as larva.

Figure 2. Corn rootworms overwinter in the pupa stage.

Figure 3. Bean leaf beetles overwinter in the adult beetle stage.

By: Rich Peters |