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Extension > Local Extension Offices > Rice > County Agriculture Educator > Articles > Fireflies aren't flies: biology and benefits of fireflies

Fireflies aren't flies: biology and benefits of fireflies

Did you know that fireflies, also known as lightning bugs, are neither flies nor bugs? They’re beetles. Coleoptera, the beetle order, is the largest of all the insect orders, accounting for approximately 40 percent of all insect species. Perhaps it shouldn’t be surprising that the firefly is a member of the vast beetle order, based on probability. But, fireflies are rather unusual and have several characteristics that make them unique among beetles.

Fireflies are in the beetle family Lampyridae, and there are approximately 200 species of fireflies from 23 genera in North America. Most North American fireflies are an inch or less in length and have soft, flexible forewings (elytra), instead of the characteristic hard elytra that most beetles possess. This anatomical difference is another reason that fireflies may not register as a beetle in most peoples’ minds.

Fireflies begin as eggs in damp soil, and once they hatch, the carnivorous larvae are ravenous. Many people don’t know what firefly larvae look like. Similar to the adult form, larvae are nocturnal, and therefore are active at night and lurk on the soil surface or under debris, unseen. They appear to be scaly or reptilian, and look rather alien with protruding mouthparts. These mouthparts are useful in eating other arthropods; larvae devour slugs, snails, and soil-dwelling critters such as cutworms. Larvae of some species can glow, and are colloquially referred to as glowworms.

Most species of firefly larvae in the United States are terrestrial and prey on several common crop and garden invertebrate pests. Because they are effective natural enemies of pests, fireflies are beneficial to have in the field and garden. After eating as many other invertebrates as they can, larvae overwinter in the soil and pupate the following spring, emerging as adult fireflies.

And of course the adults are the fireflies we all know and love. We are familiar with their twinkly luminance that inspires wonderment, and the science behind the illumination is equally fascinating. Male and female fireflies both produce light from special organs on the underside of their abdomens. The flashes of light are considered cold light because they produce little to no heat as a by-product. The light they produce is a form of luminescence, the emission of light by a substance that has not been heated. There are many ways that organisms accomplish bioluminescence, and the mode that fireflies use is well-understood.

Here’s what happens: light is created in the end of the firefly’s abdomen when oxygen combines with a substance called luciferin, calcium, and adenosine triphosphate (ATP) in the presence of the enzyme luciferase. The whole reaction takes place in special cells called photocytes. The rhythm of the flashing varies with the species and may serve to distinguish to identify males and females from one another.

Firefly biology is captivating, and while many people are intrigued by how these insects produce light, we owe equal reverence to the fact that fireflies are beneficial insects which help control pests in our fields and gardens.

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