In addition to the light displayed by lightning during thunderstorms, nature exhibits the flashing yellow lights of the lightning bug. This display of lights continues throughout the summer during the evenings.

Although commonly called lightning bugs and fireflies, they are neither bugs (order Hemiptera) nor flies (order Diptera). They are beetles (order Coleoptera). There are over 2,000 species of lightning bugs. Another common name worldwide is lightning beetles. About 170 species are found in North America with most species occurring east of the Mississippi. Lightning beetles are a joy of summer, delightful to look at and fun to catch.

The lightning beetle (Family Lampyridae) are usually a little over half-inch long and very soft-bodied. The shield-like structure behind the head is called the pronotum. The pronotum largely conceals the head when viewed from above. The reddish pronotum has a black spot in the center. The brownish-black wing covers, called elytra, are trimmed in yellow except at the front. The lower end of the abdomen is yellowish green. It is in these “taillight” segments where the flashing, known as bioluminescence, occurs.

Bioluminescence within a living organism is light produced by a chemical reaction called chemiluminescence requiring two unique chemicals: luciferin and photoprotein. Luciferin is the compound that produces light during the chemical reaction.

The bioluminescent color in lightning beetles or fireflies is a result of the arrangement of luciferin molecules. Most bioluminescent organisms are found in the ocean. These bioluminescent marine species include fish, bacteria and jellies. Some land dwelling bioluminescent organisms, include fireflies and fungi.

The glowing bioluminescent light emitted by the adults and larvae of fireflies is truly one of nature’s marvels. After mating, females deposit their eggs on or just below the soil surface. The resulting larvae have prominently segmented bodies, and like the adults, they possess bioluminescent organs located in tiny spots on the underside of their bodies. The soft, greenish-white glow emitted from these organs gives rise to the common name of “glowworms. The larvae are predaceous who are particularly fond of slugs and snails, but they will also eat smaller insects, eggs of insects and small critters in the soil (free pest control).

In Ohio, a commonly encountered firefly is probably the big dipper (Photinus pyralis) found in various habitats like roadsides and woodlands and is commonly found in open areas like yards and fields.

It is believed that larval fireflies first began producing light to warn predators that they were toxic and distasteful. The flashing lights seen at night are the courtship displays of fireflies.

Male fireflies will fly and emit a flash pattern that is unique to each species. The females, which are typically on the ground, will flash back if she finds the male suitable. The male flash pattern is used to identify firefly species.

In the case of big dipper fireflies, the males will produce a relatively long (0.6-0.8 second) J-shaped flash (thus the big dipper name) every 5 to 7 seconds when the temperature is 72-78°F. They will flash more frequently when it is warmer and less when it is cooler.

There are a variety of threats that fireflies face. The University of Illinois Extension during a research study in 2020 found that the firefly population has been declining caused by light pollution, and pesticide use. Climate change and associated issues were also highly ranked as a cause for decline.

As is the case with many insects, the habitats on which the fireflies rely have been shrinking for years. Firefly larvae need moist conditions like those found in wetlands and damp fields. In residential areas, removing leaf litter and other plant debris from yards reduces the amount of suitable habitat.

Most firefly species in the United States are crepuscular (active at dusk) or nocturnal (active at night). As the night skies get increasingly brighter, due to increasingly larger well-lit urban areas it is more difficult for fireflies to find mates. While it may not seem to some like the night skies are becoming brighter, nearly 80% of North Americans report that they can no longer see the Milky Way.

Pesticide use poses a threat to firefly populations and other insects. Remember, fireflies spend most of their lives as larvae that feed on soil dwelling pests like slugs, snails and other soft-bodied critters. Pesticides applied to the soil for various reasons depletes the fireflies food source.

Our ecosystem is a fragile environment. The geographic area where plants, animals and other organisms live in our region and our own neighborhood works together to form the bubble of life. The decline of the firefly is just a small example of the ecosystem we call life.