Perhaps because of the extremely dry conditions this summer I haven’t seen many of the little flashing beetles called fireflies. But, it’s the right time of year, especially when the humidity is high, to see their tranquil flash – flash – flash scintillate through the fields and trees. Pastures and low areas, particularly along streams, often sparkle each evening with their flickering lights.
Technically named fireflies, we called them lightning bugs when I was growing up and most folks around here still do. We scooped them out of the air with our hands and put them in a jar where we could watch them twinkle. Or, being boys and brutal, we pinched off their luminous tail segments and stuck them on our faces where they glowed for quite a time like little greenish-yellow demonic eyes.
Lightning bugs have a characteristic musty, buggy odor that in my mind’s nose I can smell even as I write this. Their smell is exactly like, well – lightning bugs. Anybody who has handled them knows just what I mean. The rest of you will just have to run out on the next lightning-buggy evening and catch some to sniff.
Over 1100 species of fireflies live in tropic and temperate areas of the world, with about 125 kinds found in the United States. Fireflies are beetles in the insect family Lampyridae. (To remember that, think of “lamp” plus “pyro” and you get “lamp fire beetle.”)
In East Texas, fireflies are usually half to three-quarters of an inch long, and the pattern of their rhythmic flashing varies with their sex and species. They flash special messages to attract mates; kind of an insect Morse Code. Some investigators have theorized that fireflies may also flash to warn off predators, but it doesn’t work with frogs that happily eat them in large quantities, probably pleased they advertise their position so clearly with their little strobe lights.
Males are the flight specialists. Females stay on the ground or on vegetation, watching and waiting. A female will only respond to a male “flasher” (Uh, you know what I mean! Sorry about that!) if his navigation lights send the correct series of impulses. Some fireflies send single, short flashes, others produce longer ones. A few kinds flash twice, pause, and then flash twice more. Still others send out three flashes in a row. The variations are almost endless. The two chat a bit by trading flashes to assure they’re both the same species, and if the code and their attitudes match, they mate.
In some tropical areas some fireflies flash in unison, hundreds at a time, with one “pacemaker” beetle setting the tempo, making it look like a whole tree filled with hundreds of them is wired with tiny Christmas lights going on and off together. Others synchronize from tree to tree, first one tree, then the next, and so on, causing waves of light to sweep across the forest.
After mating, the female lays tiny glowing eggs just under the surface of the soil that hatch in two to four weeks, into tiny predaceous larvae, called glowworms. Their diet consists mostly of small snails and worms. After a summer of eating, they overwinter in small tunnels, emerge as the weather warms in the spring, become pupae, and finally change into adult fireflies the next season.
One unusual and antisocial kind of female firefly in the United States mimics the flashes of females of a different genus, luring them in until they land close by. Then they are attacked and eaten! However, most firefly adults eat only pollen, nectar, or nothing at all, living at most about three weeks.
A firefly flashes when a chemical called luciferin (named after the Biblical Lucifer, the Angel of Light who became Satan) in their light organs combines with oxygen in the presence of an enzyme called luciferase. The light produced has virtually no heat. Almost 99% efficient, it is “cold” light as compared with that released by an incandescent light bulb of only about 3% efficiency, wasting 97% of its energy as heat. If fireflies operated that way, they’d probably fry themselves with their first love affair. An amorous Fred Firefly would signal Freda Firefly and pop!! Midair explosion followed by a flaming crash!
Although scientists know how the light is produced, and even copy the chemistry in those glowing light sticks you can buy at carnivals and that the military use to outline combat landing zones, we really don’t fully understand how they control the “on” and “off” sequences so quickly. Fireflies probably don’t care much about how it works. They just do it.
Lightning bugs are interesting for all the above reasons, but I just enjoy seeing them. There’s nothing as relaxing as sitting on the patio in a recliner on a warm summer night, dripping with sweat, and watching them twinkle across the lawn at the edge of our woods. Magic chemical lights they may be, but they are also little sparks of tranquility leisurely drifting through the fields and forests of East Texas. And with today’s hustle and bustle, anxiety, and aggression, we need all the peace we can get.
Dr. Risk is a professor emeritus in the College of Forestry and Agriculture at Stephen F. Austin State University in Nacogdoches, Texas. Content © Paul H. Risk, Ph.D. All rights reserved, except where otherwise noted. Click firstname.lastname@example.org to send questions, comments, or request permission for use.