What's Up, Watershed? Fireflies — A Magical Reason To Leave Your Leaves

Those lovely little beetles that fly around in June and light up at night…do you call them lightning bugs or fireflies? No matter their name, there’s no denying that these magical creatures have filled both children and adults with wonder for generations.  I was shocked when I learned recently that at least 18 species of fireflies are threatened with extinction due to factors like habitat loss. You might be wondering…why am I talking about fireflies in the fall?  Well, as it turns out, what you do with the leaves that fall off your trees can have a significant impact on the health of firefly populations.  If you like seeing those magnificent beauties in the summer, then it’s time to leave the leaves!  In this edition of “What’s Up, Watershed?” we’ll explain more.

Chris Bunn

Environmental Program Coordinator

Pennsylvania Resources Council

Leaf litter is the dead plant material that falls from trees, shrubs, and other types of plants.  It’s that stuff that you rake up in the fall and put out by the curb to be picked up.  Did you know that fireflies actually spend the majority of their lives in leaf litter, as well as under rotting logs, stones, and burrows?  This is in their larval stage, during which they eat common yard pests like slugs, snails, and mosquitoes. 

It’s not only fireflies that require leaf litter for survival — other magnificent insects including luna moths and various species of butterflies actually use it for cover during the winter, even disguising their cocoons to look like leaves.

As you’ve probably gathered by now, removing leaf litter from your yard also removes a vital source of habitat for fireflies, butterflies, and other native insects.  In addition, during the leaf removal process you are likely removing the cocoons and larvae of beautiful insect species. 

If you love seeing insects like fireflies during the summer or care about insect conservation, it’s time to do less yard work and leave the leaves!

Leaving the leaves in your yard doesn’t have to mean getting rid of your lawn.  One alternative would be to create a small area in your yard that is more “wild”, kind of like a forest floor.  In this area, you could place fallen leaves, logs, and other natural materials you’d normally remove.  In addition, you could rake leaves off your lawn and use them as mulch in your garden beds or around the base of trees.

Mulching with leaves has a host of benefits such as suppressing weeds and improving soil health by retaining moisture, adding nutrients as they decompose, and feeding soil microorganisms with vital organic matter.  For this process, it’s important not to shred your leaves, as they do not provide the same level of cover as whole leaves and you may be destroying eggs, caterpillars, and cocoons in the process.

To learn more about leaving the leaves and other methods of wildlife-friendly yard care, please visit this article by the Xerces Society.  To learn about other ways you can help protect fireflies in your yard, check out this brochure from the Xerces Society.  We hope that you’ll consider leaving the leaves this fall and joining the movement to protect native insects.  In doing so, you can help to ensure that your grandchildren can participate in the wonderment of catching fireflies on an early summer night.

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Thanks for sticking around, and see you next time for “What’s Up, Watershed?”! 

Photos shown above (top to bottom): fall leaves (Lawrence OP), common eastern firefly (Katja Schulz), luna moth (Patrick Randall), leaf mulching (Chris Bunn)