Insect Hibernation

by Karen Miller, Master Gardener Entomology Specialist

Have you ever wondered “where do the bugs go in winter”? Do they leave? Do they stay? Do they die? I have wondered, so I decided to do “a little digging” into it. This is what I found out. Insects are not able to generate significant heat internally to keep them from freezing. They have evolved other ways to avoid the cold weather in order to survive the winter temperatures. One way to avoid cold weather is to migrate to warmer climates. As we know, this is the strategy used by the Monarch butterfly. They will fly from the eastern United States and Canada to winter in Mexico, most times a distance of over 2,500 miles. Other butterflies and moths migrate as well, including the gulf fritillary and the painted lady. Dragonflies, that inhabit ponds and lakes in the northern states, migrate too. The common green darner is one such dragonfly. Another method of surviving the cold is to burrow into the soil or under leaf litter. Generally, the soil is much warmer than the surface. Being under the soil or beneath leaf litter keeps the insect out of the chilly winds and hidden from hungry birds. Some insects burrow beneath the frost line in large number. Termites and ants are examples of these. They also store food to keep themselves comfortable until spring. Honey bees cluster together to keep themselves and their brood warm, and ladybugs will hibernate by stacking on top of each other on stumps and under rocks to share the heat and buffer themselves against the lower temperatures. To keep her eggs safe, a female grasshopper will tunnel deep into the soil and deposit them thru the winter months. Some insects use a method of hibernation called “diapause” to survive the winter. A long term state of suspension, diapause synchronizes the insect’s life cycle with changes of the seasons in its environment, which includes the winter season. These little bugs think, if there is nothing to eat and it is too cold to fly, why not just take a break.

This break can be taken in any stage of development. Mantids overwinter in foam cased eggs. Woolly bear caterpillars curl up under thick leaf litter waiting to spin their cocoons in the spring. Certain butterflies overwinter as chrysalis, emerging in butterfly form in the warm weather. In the much colder climates some insects are able to go into a temporary sleep and are completely immobile until it warms up. Many are able to make their own antifreeze. This makes the insect more cold tolerant by allowing its body fluids to drop below freezing points and protecting its tissue and cells from damage. There are many answers to the question “Where do the bugs go in winter”. In Texas many insects do not die off. Texas does not stay cold enough, for any length of time, to totally kill many insects. Some do die from the shock of cold weather, but this will not eliminate whole populations. BOTTOMLINE...Just because we get a freeze or two does not mean all insects will die. When the sun comes out and warms everything up, we will see them out and moving around again. 3-3-2016