ZOO-ology column: Natural flashers

By Judie Farnsworth
Sept. 16, 2012 at 4:16 a.m.
Updated Sept. 17, 2012 at 4:17 a.m.

Glowworms use their luminescence to warn about their terrible taste and can increase the intensity when disturbed.

Glowworms use their luminescence to warn about their terrible taste and can increase the intensity when disturbed.

Catching fireflies on a warm night is a happy summer memory for many people. Fireflies are actually beetles of the Lampydrea family.

Did you know that not all species are luminescent? But those that are give "you light up my life" a whole new meaning.

What makes a firefly glow? It's a combination of oxygen and a substance called luciferin. They combine in an area beneath the abdomen where there are special cells and light organs.

The flashes are often species specific meaning there is a particular pattern of flashes for a species. Some species even synchronize their flashes.

Imagine a whole field of synchronized blinking. It's a rare sight, but it does happen. Could it be insect Olympics?

Scientists have yet to find the on/off switch and, yes, even the dimmer switch. Nearly 100 percent of the blinking energy is given off as light and not wasted as heat. Compare that to a light bulb where some 90 percent of the energy is given off as heat.

Some adult fireflies protect themselves by using what is called reflex bleeding. Their blood contains bitter chemicals; some may even be poisonous to other animals. If threatened, they may shed a drop of blood that will taste awful to a predator and hopefully allow escape.

The firefly starts life as a larva and winters underground during the larval stage. At this point, it's called a glowworm. It really does glow even if the eventual adult species does not. It's believed that glowworms use their luminescence to warn about their terrible taste and can increase the intensity of their glow when disturbed.

Both male and female fireflies use their flashing lights to attract a mate, discourage predators or defend territories. A female will wait patiently for a male with just the right glitz to catch her eye.

Alas, there always seems to be a rotten apple within a group and fireflies are no exception. There is a Photuris species also known as femme fatale fireflies. The female doesn't play by the normal rules. She chooses an unsuspecting male, mimics the mating flashes of his species and pounces. Instead of a date, he becomes a dinner. The female in addition to dinner, gets a bonus dose of luciferin.

In recent years fireflies have been noticeably fewer worldwide and studies are proving quite interesting. One of the possible reasons for a firefly decline is light pollution. This is really something to ponder. Light from homes, cars, stores, streetlights make it difficult for fireflies to signal during mating. The extra flashes of human light sources may affect the patterns. Scientists don't know enough about these creatures to be sure, but the indications are pointing to light pollution as a possibility.

Firefly larvae thrive in forest litter, rotting wood, marshes and by ponds and streams. These previously remote areas are being lost to housing and commercial areas. If you should catch these little sparklers.make a wish for their survival and let them go.

To learn more, visit en.wikipedia.org/wiki/Firefly and firefly.org/

Judie Farnsworth is a longtime volunteer at the Texas Zoo specializing in educational programs.



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