By Donald Lewis
Extension Entomologist
Iowa State University

We were lucky in central Iowa this year to have had a decently-long autumn to enjoy. My measure of the length of the season is how long the katydids continue to sing in the treetops at night in my neighborhood. This year I heard the last katydid of the year on Nov. 2. He was a lonely, cold, and pathetically-slow old guy, but there he was, in a tall tree on the golf course, rasping out his zit-zit-zit song one last time hoping there was still a female within hearing distance. I don't known if she answered his call or not, but I do know I admired his tenacity and his effort.

But where is he now that the trees are bare of leaves and temperatures have fallen below freezing? What has become of the millions of millipedes, the gazillions of Japanese beetles and the thousands of tiger swallowtails that were here just a little while ago?

No doubt about it. Winter can be a tough time to be alive in Iowa. Animals and plants that live and prosper here do so by having some “trick” to escape periods of inhospitable weather, and winter can certainly be inhospitable, especially for cold-blooded animals such as insects, snakes, frogs and turtles. For these animals the body temperature varies with the environmental temperature. When it is hot, insects are hot. When it is cold, insects are cold. And when it is very cold, insects are dormant.

Dormancy is an inactive state when insects stop moving, stop eating and stop growing until better weather returns. As a broad, general rule, insects are dormant at temperatures lower than 45 degrees F.

But not all stages of all insects are capable of dormancy, or have the ability to survive the long, freezing-cold Iowa winter. Different insects spend the winter in different life stages. Most insects have four life stages, egg, larva, pupa and adult. Some, like the katydids and their relatives the crickets and grasshoppers, have only three stages, egg, nymph and adult.

Some insects hibernate through the winter in the adult stage. Certain butterflies and moths, the baldfaced hornets and the squash bugs hunker down in a protected location and wait for warm temperatures to return before they fulfill their biological destiny and produce the next generation of their species. Some insects get the reproducing done in late summer and leave the eggs to survive the winter to hatch next year and start the life cycle over. The eastern tent caterpillars that build silken webs in crabapple and plum trees will be here bright and early next spring because the female moths have already laid their eggs on the caterpillar host trees. And the eggs of the bagworm common on conifer trees in the southern half of the state are in the pods of the previous generation left hanging on the trees.

Those Japanese beetles that were eating the foliage and flowers from your grapes and roses last July have all died. But their offspring, the white grubs, are now several inches deep in the soil where they will survive the winter and finish development to the adult stage next June.

Finally, some insects make it to the pupal stage in the fall and then wait till spring to complete the metamorphosis to the adult stage. The cecropia moth, the black swallowtail and many other lepidopterans are out there in the garden, in the cocoon or chrysalis, withstanding below freezing temperatures, waiting for spring.

As you might guess, insects that survive the winter need a mechanism to protect against freezing. Those that make it are protected by antifreeze-like compounds that keep ice from forming in the body. Iowa insects are better equipped for this frigid time of year than are we!

So what about the lonely katydid? By now he has succumbed to freezing or old age, whichever came first, but before he and his mates died the female had glued her eggs to tree stems where they will survive until next summer. After they hatch it will take another six to eight weeks for the nymphs to grow and for the adult males to start singing in the tree tops again. I can't wait.

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