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Habits and Traits of Fireflies, Family Lampyridae

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Viewed from above, the firefly's head is obscured by a shield-like pronotum.

Viewed from above, the firefly's head is obscured by a shield-like pronotum.

Photo: Fritz Geller-Grimm/Wikimedia Commons (CC by SA license)

Who hasn’t chased a blinking firefly on a warm summer night? As children, we captured their luminescence in glass jars to make insect lanterns. Unfortunately, these beacons of childhood seem to be disappearing due to habitat loss and the interference of manmade lights. Fireflies, or lightning bugs as some call them, belong to the family Lampyridae.

Description:

Fireflies are usually black or brown, with elongate bodies. If you handle one, you'll notice they feel somewhat soft, unlike many other kinds of beetles. Hold it gently, as it's quite easy to squish. When viewed from above, the Lampyrids seem to conceal their heads with a large shield. This feature, an extended pronotum, characterizes the firefly family.

If you examine the underside of a firefly, you should find the first abdominal segment is complete (undivided by the hind legs, unlike in ground beetles). In most, but not all fireflies, the last two or three abdominal segments look quite different from the others. These segments are modified as light-producing organs.

Firefly larvae live in moist, dark places – in the soil, under tree bark, and even in swampy areas. Like their adult counterparts, larvae glow. In fact, fireflies produce light in all stages of their life cycles.

Classification:

Kingdom – Animalia
Phylum - Arthropoda
Class – Insecta
Order – Coleoptera
Family – Lampyridae

Diet:

Most adult fireflies do not feed at all. Firefly larvae live in the soil, preying on snails, grubs, cutworms, and other soil-dwellers. They inject their prey with digestive enzymes that paralyze and break down the bodies, and then consume the liquefied remains. Some fireflies eat mites or even pollen.

Life Cycle:

Fireflies typically lay their eggs in damp soil. Eggs hatch within weeks, and larvae overwinter. Fireflies may remain in the larval stage for several years before pupating in the spring. In ten days to a few weeks, adults emerge from the pupal cases. Adults live just long enough to reproduce.

Special Adaptations and Defenses:

Fireflies are best known for their coolest adaptation – they produce light. Male fireflies flash their abdomens in species-specific patterns, hoping to attract the attention of a female hiding in the grass. An interested female will return the pattern, helping guide the male to her in the darkness.

Some females use this behavior for more sinister means. A female of one species will purposefully mimic the flash patterns of another species, luring a male of another kind to her. When he arrives, she eats him. Male fireflies are rich with defensive chemicals, which she consumes and uses to protect her eggs.

Most females don't practice cannibalism, though. In fact, since females live just a few days spent waiting in the grass for a mate, some don't even bother to develop wings. Firefly females may look just like larvae, but with compound eyes.

Many fireflies use foul-tasting defensive compounds to deter predators, like jumping spiders or even birds. These steroids, called lucibufagins, cause the predator to vomit, an experience it won't soon forget when it next encounters a firefly.

Range and Distribution:

Fireflies live in both temperate and tropical climates throughout the world. About 2,000 species of Lampyrids are known globally.

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