The Curious Case of Insects in Winter

The Curious Case of Insects in Winter

With the recent flurry of warm weather we’ve had here in northern Illinois, it’s not uncommon to see some insects appearing around homes and natural areas.  In just the past few days a wooly bear caterpillar, a few Japanese ladybeetles, a solitary honeybee, and even a cabbage white butterfly have made their spring debut!  While it’s exciting to know that spring is around the corner with its warm weather and gorgeous ephemeral flowers, it can make you wonder: where have these insects been all winter?

It’s important to remember that insects are ‘ectotherms,’ meaning that they depend on external heat sources like the sun to warm their bodies.  That means in winter, most insects would be too cold to move around, feed, pollinate, or perform almost any of their normal activities.  While there are some rare exceptions like winter stoneflies, which emerge and are briefly active in winter, most insects will need to find some way to escape from the cold.  Over time, insects have developed three general ways to survive through the winter until the spring flowers are blooming.

If you’ve ever thought about taking a trip to Florida in winter, then you’ll be familiar with the first strategy: migration.  Some insects simply leave cold locales in winter and find some warmer place to exist until temperatures warm up in spring.  Likely the most well-known example of a migrating insect is the monarch butterfly, one of the most distinctive butterflies in the Midwest and one that can be supported by planting native milkweed and nectar flowers.  Monarchs spend the summer throughout the Midwest and southern Canada, and in fall start a 3,000-mile migration to their overwintering habitat in the mountains of Mexico.  In spring, they reverse this migration and begin traveling north during the growing season, when their offspring will have milkweed to feed on.  However, monarchs aren’t the only insect to migrate.  Some local dragonflies, including the large and distinctive green darner, migrate to and from the Upper Midwest as well, chasing those warmer temperatures. 

The second strategy is one that we use ourselves, which is to find somewhere warm and protected indoors to stay in the winter.  If you were to take a close look around your home, especially in the dark, quiet corners of garages, sheds, and attics, you may see a variety of adult insects calmly waiting out the winter months.  They do not feed and are extremely inactive during this period, almost in a state of hibernation as an effort to preserve their energy stores until the spring.  Some insects that use this method include stink bugs, mosquitoes, ladybeetles, and occasionally some butterflies like the mourning cloak, which is why they’re often the first adult butterfly we see in spring.

The final strategy is to stay the winter outdoors, but in a life stage that is better suited to winter survival.  For example, many aquatic insects such as mayflies and dragonflies are still out in natural areas, but only as aquatic larvae at the bottom of our local lakes and streams.  Much like fish, they can avoid freezing surface temperatures by staying further down in the water column.  Many of our local beetles, moths and butterflies will overwinter as eggs in the leaf layer of forested habitats, or as pupae and cocoons stuck onto woody stems.  Existing as the better insulated eggs and pupae give these insects a greater chance of surviving over the cold winter months.

One thing that is common amongst the winter survival strategies of insects is that when temperatures warm up and they migrate back, or emerge from indoors, or hatch from their eggs, many are going to need energy in the form of nectar and pollen.  Some of the earliest-emerging pollinator species, such as the federally endangered rusty patched bumblebee, depend on early spring ephemeral flowers for their queens to obtain energy to build their nests for the year.  These early-season plants are often an overlooked necessity in pollinator lifecycles but are critical to their survival for the year and are species we have extensive experience with using in natural areas restoration.  Let us help you by providing consultation, and determining if spring ephemeral flowers would benefit your native plantings.   By working together managing your natural areas restorations, we can ensure that people and insects both have something to look forward to this spring!

 Andres Ortega

Ecologist

Leave a comment

Please note, comments need to be approved before they are published.