Picture walks: Mourning cloak butterflies

A mourning cloak butterfly. Photo by Jeanne Church.

By Jeanne Church

If butterflies played the game of Survivor, mourning cloaks would probably win! The average life span for most butterflies is around one month, but mourning cloaks often survive for 10! Amazingly, they spend the better part of their adult life enduring our cold Michigan winters! Through snow and wind and freezing rain, mourning cloaks tuck themselves away in tree cavities, leaf litter, cracks in rocks, loose bark, and the crevices of unheated buildings to survive. 

Sometimes, during March and April, on those rare occasions when our temperatures exceed 60 degrees, these butterflies will venture out to feed on tree sap, particularly from oak and maple trees. Once the cold temperatures return, they will head back to their hiding places and wait for warmer weather to return.

I spotted my very first “winter” mourning cloak in late March of last year. There was still snow on the ground, but it was an amazingly warm 65-degree day! I had been walking along a wooded path at the Wolf Lake State Fish Hatchery in Mattawan when a solitary mourning cloak landed on a nearby sign. That first encounter with a winter butterfly totally surprised me! I had no idea that some butterflies could be out and about while there was still snow on the ground and wondered how that was even possible.

Apparently, butterflies that overwinter enter a state of existence known as diapause; a type of hibernation for bugs. Mourning cloaks shut down all their non-essential systems like reproduction, and slow their metabolism dramatically. They also have special chemicals in their bodies that work as a type of anti-freeze. Butterflies that don’t overwinter as adults will spend our snowy, frigid days in one of three other life stages: as an egg, a caterpillar, or a chrysalis. Other butterflies, like the monarch, will just find a more hospitable place to spend the winter than Michigan!

You can look for mourning cloaks during May and June, particularly in wet, wooded areas. After that, they will be harder to find as their eggs hatch into caterpillars, and their caterpillars transform into butterflies. The butterflies will then “sleep” through our hottest months of summer for a period of dormancy called aestivation. In late summer and early fall, you can look for them again as they flutter about seeking nectar and other nourishment to help sustain them during the snowy months ahead.

If you want to help overwintering insects like mourning cloaks, you can start by not cleaning up your yard too early! Leave all that leaf litter beneath your trees and in your gardens. It’s likely to contain overwintering caterpillars, eggs, or adult butterflies. If you find what looks like a dead chrysalis in your garage or garden shed in the winter, leave it where it is. The butterfly inside may well emerge when spring comes along. You can also set up a fruit feeding station in the spring with overripe bananas, cantaloupe, or rotting fruit that will provide sustenance for the mourning cloaks and other butterflies that have been overwintering.

Also, if you want to make your yard more attractive to mourning cloaks all year long, try planting some of their favorite trees like willows, cottonwoods, aspens, poplars, birches, hawthorns, elms, hackberries, or mulberries. These are host plants for mourning cloaks where they like to lay their eggs.

Even though these superstar survivors are considered plentiful across their range, mourning cloaks are still at risk of decline from insecticides and habitat loss! It’s vitally important that we all work to maintain as many natural areas as we can, and that we refrain from the widespread use of insecticides!

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