The Say’s Firefly became Indiana’s state insect when legislation proclaiming it as such was signed by Gov. Eric Holcomb on March 23, 2018. Photo from Indiana Department of Natural Resources.

By Jeff Burbrink
Ag & Natural Resources Extension Educator, Purdue Extension LaGrange County

LAGRANGE — Joe Boggs and Ashley Kulhanek, of Ohio State’s Extension Service, recently wrote some fascinating stories about fireflies, as known as lightening bugs. As a kid, I was fascinated with lightening bugs, and I am excited to pass along these interesting tidbits about one of America’s favorite insects.

Jeff Burbrink

There are about 25 different species in our general area, with more than 2000 separate species worldwide. The family name, lampyridae, refers to the ability of the group to produce light, also called bioluminescence. In many of these species, the larva also emits a glow. I have found glowing larva under leaf litter in my woods and near my pond.

There are several species of fireflies that do not emit light at all as adults. If you have ever stumbled across a firefly in broad daylight, most likely you have encountered this version of firefly. These non-glowing adults feed on pollen and nectar, and are often found on trees. Their younger, larval stages, however, do emit a glow. Our familiar nighttime fireflies tend to hide during the heat of the day.

It’s thought that the glow emitted by the larva and adults helps protect them from predators. Think of the glow as a warning that eating the lightening bug could be their last meal. They contain a toxin called bufadienolide, a steroid-like substance also found in some species of toads. In fact, there is a documented case where two bearded dragons (a lizard species from Australia) were fed fireflies at a US zoo and died within 90 minutes of the meal!

In adult fireflies, the primary reason for the flashing appears to be attracting a mate. Each firefly species that flashes has its own light pattern, including some that glow a light blue color for weeks at a time.

There are even species of fireflies that have the ability to sync their flashing. In the Smoky Mountains of Tennessee, there is a species (photinus carolinus) that has become quite famous, inspiring hundreds of visitors to the forest they inhabit. The males have developed the ability to turn off in unison, then reignite their light, giving the appearance of being in sync.

The larval form of most firefly species live 1 to 2 years in our soil, often under leaf litter in the forest or in grassy meadow-like areas, whereas adults only grace us with their presence for 4-6 weeks in June and July in Indiana. By careful sifting through soil in these locations, you might locate a glowing larva and impress your kids or grandkids!

Some observers have noted a decrease in firefly numbers in recent years, especially in areas where mosquitoes are routinely sprayed. Mosquitoes and fireflies tend to thrive in the similar habitats. Leaving leaf litter undisturbed, while reducing disruptive tillage and other soil disturbances can go a long way to protecting the larva and pupa that eventually produce the adult fireflies that grace our evening sky.