Into the Wild

Waking up the Butterflies

The first butterflies of spring get a jump on the season by hibernating as adults.
Get in on the vernal optimism of these early risers!

Compiled by Doug Taron

Butterflies in Winter?!

It’s a little known fact that some butterflies of Chicago Wilderness spend the winter as adults. Species such as the mourning cloak, eastern comma, and Milbert’s tortoiseshell become adults in the fall, then find sheltered spots to last out the cold. They hibernate in piles of leaves, hollow logs, and under loose bark on trees. Sometimes they seek out a crevice under the eaves of an unheated garage or tool shed—even a discarded can. On warm days in early spring, these butterflies are often the first to emerge. They can even be seen, though rarely, flying over ground still covered with snow.

Erratic Timing

The first appearance of butterflies has all the consistency of spring weather in Chicago. It can be as early as February or as late as April. Sporadic sightings can even occur in January, though this is very rare. The thermometer is a more reliable tool than the calendar in figuring out when to begin looking. Butterflies require a body temperature of about 60° F or more to fly. They can sometimes be seen when the air temperature is cooler if they are in a place where the sun can heat them up. In contrast, if they are in a very dark location, such as inside of a hollow tree, they may be unable to warm up enough to fly even on warm days.

Where to Look

The two most common species of butterflies that can be seen in very early spring in the Chicago area are the mourning cloak and the eastern comma. These butterflies can be found in many different places. Indeed, early sightings of these species have been recorded in urban habitats such as Chicago. If you are really craving the sight of a butterfly after a long winter, however, your best bet is to go for a walk in the woods. Woods that have good displays of spring wildflowers or large patches of nettles (the caterpillar food plants for eastern commas) are often good spots.

Feeding in a World without Flowers

In some years, a warm spell in early March means that butterflies are out and about before there are flowers for them to sip nectar from. Finding an energy source can be a challenge. Pussy willows are among the earliest food sources for mourning cloaks. Bridle trails through woodlands can be excellent places to see early spring butterflies because they will sometimes sip salts and nutrients from horse dung. They also seek out sugary sap flowing from trees, especially box elders and other maples.

Hot Spots

To try to get an early glimpse of one of the very first butterflies of spring, seek out a path through woodland that’s reasonably far from the cooling influences of Lake Michigan. Some good choices include Harms Woods, Morton Arboretum, and forest preserves in the Palos area. Even on a warm day, the butterflies will need time to warm up and become active. An early afternoon visit will improve your odds of success. Don’t expect to see lots of butterflies very early in the year. A half dozen during an hour’s walk is not out of the question, but even a glimpse of a single mourning cloak will be a welcome sight after a long winter.

Secret to Success? Natural Antifreezes

It’s challenging for a cold-blooded animal like a butterfly to survive the winter without freezing to death. Natural antifreezes, like glycerol, are chemically very similar to the antifreeze in a car. They prevent ice crystals from forming and damaging the cells in a butterfly or caterpillar’s body.

The Question of the Question Mark

The question mark is a very common butterfly in Chicago Wilderness. It spends the winter as an adult, and is sometimes mentioned as a species that can be seen early. Yet it’s very rarely seen with the mourning cloaks and eastern commas on the first warm days of spring. Reports of migration in this species may suggest that they fly further to the south before settling down for the winter. The details of this story are still unclear, and could emerge due to the efforts of committed butterfly watchers.

Sugaring for Butterflies

To attract butterflies, make a paste by mashing overripe bananas with flat beer, a bit of rum, fruit juice, and molasses and spread it on a stump or tree trunk in a sunny spot in a woodland. If you are lucky, you will attract some butterflies as well as moths. Sugaring can be a good way to find less abundant species, such as Milbert’s tortoiseshells.

Related Articles:

Restoring the Butterfly Tapestry, CW Summer 2004

Great Butterfly Sites, CW Summer 2008