Wild Profile: Meet the firefly

Published: June 23, 2020

Close-up of a firefly By khlungcenter/Shutterstock

When not in a glowing cloud of its cousins, a firefly looks like pretty much any other bug. That’s because the insects are, in fact, ordinary old beetles. Well, may not so ordinary: fireflies have “light organs.” They can self-illuminate, producing bursts of bioluminescence (light), thanks to two chemicals—luciferin and luciferase—that interact with oxygen inside their bodies.

Fireflies use their flickering lights like Morse Code, to communicate with potential mates. Males usually flicker while in flight; females stay low to the ground, waiting for signals, and responding to them. Fireflies produce yellow, green, or orange light, in a variety of different flicker patterns. It depends on the species. One type of firefly might produce a quick flash of green, followed by a long glow; another might flash orange every three seconds.

This firefly time-lapse video will take your breath away.

A firefly’s light is efficient; one bug only loses about two per cent of bioluminescent energy as heat when its body lights up. An incandescent light bulb, on the other hand, can lose 90 per cent of its energy as heat. If only fireflies could power our lights! Of course, it would take about 25,000 bugs to produce the same glow as a 60-watt bulb.

Some research suggests that fireflies also use their flashing lights to ward off predators.

Pre-birth, fireflies even glow inside their eggs. They hatch in mid-summer, and, as larvae, feed on worms, slugs, and snails. The larvae produce venom strong enough to paralyze larger prey, and liquefy their innards. Worm Slurpee, anyone? The larvae don’t change into flying adult bugs until the following spring at the earliest. Most adults don’t eat—some only live for about a week, after all—but females of the genus Photuris do. On the menu? Other fireflies. Females mimic the flashing light pattern of smaller species, lure in the males, and then eat them.

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