A larva with light: Can you guess what insect this is?

The end of June brought a very exciting event. As I was cutting holes in the landscape fabric to plant some late-season flowers in my high tunnel, I found several larvae of a great beneficial insect! I guess it was the perfect environment, as I found at least 10 that evening. It was moist, although in the photo it looks pretty wet because I was running my drip irrigation water. When I found it, I was so ecstatic that my 5 year old daughter thought something bad had happened with all my yelling! I then shared a photo with my whole family. Needless to say, no one else seems to get quite as excited as I do about good bugs. Below are some photos from that special evening. Do you know what it is? Have you ever seen one? I’ll give you a few clues so you can see if you know what it is.

  1.  As larvae, they are incredible predators of many ground dwelling garden pests, like snails and slugs! 
  2. The adult form is a beetle so they have a complete life cycle —  egg, larvae, pupa, and adult!  
  3. Size: approximately ¾’’. 
  4. The larvae and adults have bioluminescence, an amazing ability to “light up”.  

That’s right, the last clue should have given it away. This is a larva of a lightning bug.

Did you know lightning bugs, also called fireflies, are actually beetles? They bring joy to everyone with their beautiful displays of flashing lights. Lots of additional information about them can be found here: https://www.xerces-dev.org/endangered-species/fireflies/about

Adult beetle. Photinus pyralis, known by the common names common eastern firefly and big dipper firefly

So where could you find these awesome critters in your landscape? Most species have at least a 2-year life cycle, and 95% of their life is in larvae form. Most adults only live 2-4 weeks. They like moist, dark areas near the soil surface, since that will be where they find their next meal.  Sometimes they even hide in the crookes and crevices of tree bark. 

Below are some actions you can take to create a habitat to attract fireflies. This information is provided by Firefly.org.

  1. Eliminate light pollution in your landscape (turn off unneeded outdoor lights, keep your curtains drawn). Fireflies use their flashing patterns to attract mates. Extra lights can disrupt their ability to find each other. 
  2. These critters thrive in wet areas around ponds, streams, wetlands, and swampy areas.  Add a water feature to your landscape if you do not have natural sources. 
  3. Avoid pesticides, especially broad-spectrum insecticides which kill many types of insects indiscriminately (even the beneficial ones). 
  4. Do not over-mow your lawn (taller grass gives fireflies a place to hide during the day). 
  5. Dead logs and leaf litter provide great habitat, so try to create an area in your landscape that has a  natural area with these materials. 
  6. Plant native trees and native grasses to provide shaded habitat. Shade helps conserve soil moisture which attracts food sources for firefly larvae.  

My family is lucky to live in a rural area near a small stream and swampy area, so we are blessed to see a wonderful display of fireflies for several months each year. Check out my blog from last summer:  Firefly or Lightning Bug: You Decide!  

By Ashley Bodkins, Senior Agent Associate and Master Gardener Coordinator, Garrett County, Maryland, edited by Christa Carignan, Coordinator, Home & Garden Information Center, University of Maryland Extension. See more posts by Ashley and Christa.

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