The Back Porch


The first insects of spring

Illustration by E.R. Jenne

This story is featured in Montana Outdoors March–April 2016 issue

Mourning Cloak.Believe it or not, winter will end someday. 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 and begin to crawl or fly.

Insects have different ways of 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. Many simply go dormant.

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

In late winter or early spring—about now—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 very few butterfly species that survive winter in the adult stage. Because their wings are dark brown, they absorb heat energy from the sun and fly on warm late-winter days.

Mating takes place in spring, after which the female produces a mass of eggs that metamorphosize to caterpillar to chrysalis (also called pupa) to butterfly by late June to early July. That leaves enough time for an adult moarning cloak 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 an ice cube, insects have evolved a variety of winter survival methods. Some isolate water inside their body into small drops; the smaller the drop, the lower the freezing point.

Also, chemicals in some insects act like antifreeze, lowering the freezing point or preventing further freezing once ice crystals form.

Then there are aquatic insects, which remain active in streams that stay open. Stoneflies mate and lay eggs in winter. Caddis flies and crane flies mate on warm winter days. Ask any Missouri River fly angler about midges hatching on a mild February afternoon that has 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 emerges from dormancy to start a new colony, which lasts only through summer but produces several potential queens to overwinter and start new colonies.

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

Bruce Auchly manages the regional Information and Education Program in Great Falls.