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The Insects Are Here

March 10, 2011 | by Bruce Auchly

The adult mourning cloak butterfly is an early
spring emerger and Montana's state insect.
Photo courtesy BugwoodWiki.

Believe it or not, winter will end some day. And when that day arrives the first harbinger of spring will likely be a bug.

Before bears emerge from their dens, songbirds return to find a nest site and flowers bloom, an insect will stir to crawl or fly about.

Insects have different methods for coping with winter. Bees eat their stored honey, shiver and move about in a tight ball, raising the temperature in the hive. Some insects dig below the frost line. Others survive by changing the way their body functions. And many simply go dormant.

Take the mourning cloak butterfly, which is Montana’s state insect and an early season emerger. This beautiful butterfly, which became the state insect in 2001, derives its name from the dark brown mourning cloaks once worn to funerals.

In late winter or early spring, the adult mourning cloak awakens from a dormant state in its winter hiding spot, usually under a bit of tree bark.

The mourning cloak is one of the very few butterflies that survive winter in the adult stage. Because their wings are dark brown, they are able to absorb heat energy from the sun and fly on warm late winter days.

Mating takes place in spring, with the female producing a mass of eggs that go through a metamorphosis from eggs to caterpillar to chrysalis to butterfly by late June to early July. That leaves enough time for an adult to feed and prepare for winter.

Perhaps the most fascinating insects are those that change the way their body functions.

An insect is basically a small, cold-blooded, liquid-filled box. Because its skeleton is on the outside of its body, an insect’s internal organs float in a fluid that’s mostly water.

To avoid becoming simply an ice cube, insects have evolved a variety of survival methods. One way is to isolate water inside their body into small drops; the smaller the drop the lower the freezing point.

Also, chemicals in the insect act like antifreeze and lower the freezing point or prevent further freezing once ice crystals form. At this point activity stops.

Then there are aquatic insects, which carry on their activities in streams that remain open. Stone flies mate and lay eggs in the winter. Caddis flies and crane flies mate on warm winter days. Ask any Missouri River fly fisher about midges hatching on warm winter days with a mix of sun and clouds.

Still other insect populations leave a single member to start anew. Bumblebees provide an example. A single previously fertilized queen bumblebee will emerge from dormancy to start a new colony, which only lasts through the summer but produces several potential queens to overwinter and start new colonies.

Whatever method insects use to overwinter, they have evolved strategies to survive and signal warmer days are ahead.