OCTOBER
1998

 

 

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

 

 

 

 

10-22-98

Winds of Winter Not Favorite Thing to Insects

Two of Maria's favorite things in "The Sound of Music” were "snowflakes that stay on my nose and eyelashes and silver white winters that melt into spring.” Not so to insects. Everything about winter is a life-and-death matter to many animals, especially insects.

Insects are cold-blooded creatures that generally cannot control their body temperature; therefore, they can't function in winter. As the poet Aileen Fisher once wrote about insects: "None has the least little urge to know what the world is like when the sky says ‘snow.'”

So, these six-legged creatures have several approaches to surviving winter conditions. A few, like many other animals, move to warmer climates during winter. The monarch butterfly is the best known of the insects that migrate. The monarch prefers the cool, but not freezing, temperatures of the mountains of Mexico to a more northern exposure to winter.

Many insects try to survive winter and fail. These unsuccessful snow bugs include the well-known moth, which is a cutworm in the immature stage. Known as the black cutworm, it goes into the winter in many stages, none of which survive. So each spring, the black cutworm population is replenished by migrants from more southern climes.

Many other insect species also die during the winter and ride the winds of spring back into northern areas. Included are some plant pests called aphids and leafhoppers. The small green leafhopper that manages to come through our window screens and die in our light fixtures is a summer resident only. 

Most of the insects that we encounter each summer do manage to survive the local winters. Some of these insects live in the soil and move deeper as the soil freezes. White grubs that damage our lawns is such an example. They just dig deeper and stay below the frost line. When the spring thaw arrives, they reverse the movement and come back to the surface.

Many adult insects that go into winter seek some shelter from the environment. Several species of insects actually take up residence in our homes, much to our concern at times. Ladybugs move in great numbers into protected places during the winter. That protected place is frequently under the bark of a dead tree, under a stone or in the leaf litter. Sometimes, the ladybugs mistake our houses for a dead tree or stone and move in with us.

Ladybugs are not the only winter intruders in our homes. We also can find a fly called the cluster fly in great numbers, hibernating in wall spaces and attics. The same is true of some paper wasp queens. These ladybugs, flies and wasps frequently show up inside our homes, attracted by the warm temperatures within.

Many other insects survive winter in the egg, larval or pupal stages. Many times the eggs are located in protected sites. For instance, eggs of the corn pest, the corn rootworm, are snug in the soil where the female placed them. Eggs of the praying mantid are encased in a foamy covering and attached to a stem where they will stay until the next spring.

Many overwintering larvae also are located in protected sites. European corn borer caterpillars stay inside the corn stalk until the warmth of spring causes them to go into the pupal stage. Woolly bear caterpillars crawl around and find a nice protected place such as in plant trash or even in hay in a barn.

Many caterpillars change into pupae as winter approaches. Some hide in the soil; others spin a cocoon and sleep in a silk blanket during the snowy days of winter.

All of these insects are winterized. They produce a natural antifreeze that keeps their cells from freezing when the temperatures drop below 32 F. The chemical is glycerol, very similar to the antifreeze materials used in automobiles to keep radiators from freezing.

To insects, the approach of winter means winterize and hibernate. The sign outside a cocoon covered with snow just might read: "Snug as a bug in a rug! See you next spring!”

 

Writer: Tom Turpin
Editor: Olivia Maddox