Every fall, the topic of what type of winter we will have is popular. The winter weather predictions are often followed by the comment that we need a cold winter to get rid of some of these bugs. Do we really want that cold of a winter? Insects have winter survival strategies that have been in place of many centuries.
Migration is a common strategy and can have several meanings. The monarch butterfly is famous for its migration far south to warmer climates. The woolly bear caterpillar migration is monitored each fall as it crosses the streets looking for a better place to spend the winter. The fall armyworms don't migrate to the south, but die at the first freeze, and then a fresh group of moths migrate from the south each spring.
Some insects that don't migrate remain active in the winter, while others go into dormant state called "diapause." Some insects that spend the winter in diapause can withstand temperatures as low as minus 94 degrees.
Most insects that go dormant are considered either freeze-susceptible or freeze-tolerant. Freeze-susceptible insects avoid freezing altogether by producing antifreeze compounds that super cool body fluids and keep them above their freezing point. Freeze-tolerant insects don't really freeze. They have developed the ability to force water out of their cells during the freezing process, thus lowering the freezing point even further.
Insects pass through several stages of growth before beginning a new generation. Most insect species overwinter in a stage of growth best adapted to cold temperatures. Some insects improve winter survival by building protective structures, such as cocoons or pupae. Winter conditions play an important role in survival of insects. Snow cover provides insulation from winter cold. Light, fluffy snow offers more insulation benefit than packed snow. Wet soils cool slower than dry soils; however, saturated soils may suffocate overwintering insects.
Temperature duration intensity and timing are important factors in insect survival. If exposed long enough, an insect will die at moderately cold temperatures. On Jan. 18, 1930, a record low temperature for Tahlequah was set at minus 23 degrees. That probably froze many overwintering insects, but many still remain. The cold-for-a-time and then warm-for-a-while winters offers relief for the insects and allow them to survive in greater numbers. Also, the surprise late freeze that we experienced in April 2007 froze many insects.
Diapauses termination (when to come out of hibernation) is a factor that has been studied by many entomologists. With so many variables affecting winter insect survival, it is easy to see why so many instances where they are used in folklore to help predict the winter.
One thing we can be assured of: "The worse the winter for insect survival, the more miserable the winter for humans and animals."
Roger Williams is an agriculture educator for the Oklahoma Cooperative Extension Service in Cherokee County.