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Fireflies: Evening Lights
| Article
# : |
10927 |
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Section : |
Natural Science
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| Issue
Date : |
7 / 1986 |
1,092 Words |
| Author
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Barbara Tufty
Barbara Tufty is a free-lance natural science writer
who lives in Washington, D.C. |
On soft summer evenings as night descends along streets and gardens, over fields, and at the edge of woods, bits of magic appear. Silently in the deepening twilight, small twinkling lights rise above the grasses.
The yellow-green glow belongs to fireflies--flying beetles whose cool illumination was mystifying the Chinese as long as 3,000 years ago. Even today, with modern high technology and powerful computers, humans still cannot create the kind of light they so charmingly flaunt. Their mechanism is nearly 100 percent efficient, while our light bulbs still waste about 80 percent of energy as heat. Firefly light is in the zone of the electromagnetic spectrum to which the human eye is sensitive, a narrow belt of 5180 to 6560 angstrom units, from yellow-green to orange-red.
These nocturnal luminous insects, also called lightning bugs, belong to the beetle family Lampyridae. Of the some 3,000 species throughout the world, 100 species live in the United States, mainly east of the Rocky Mountains. They live underground for a year or so as larvae, eating slugs, earthworms, and snails. When summer comes, they crawl from the ground and take on their adult form--neat-looking, slender insects, about a half-inch to a full inch long. During the day they sleep or hide under foliage, but when twilight casts its shadows across the land, the males start wafting upwards, silently dipping up and down, and flashing their complex signals of light produced by chemicals in their bodies.
The blinking lights are intricate codes of communication between males and females. Each species has its distinct mating signal, differing from those of other species in color and in number, duration, and frequency of flashes, as well as in the shape of the flight path while the light is on--shapes resembling a J or an S or other figure. Some flashes can be as long as 30 minutes. Others are as short as 40 milliseconds, beyond detection of the human eye, explained Dr. James E, Lloyd, Department of Entomology at the University of Florida at Gainesville. With penlight, electronic firefly gun, flashing fishing pole, and plenty of patience and perseverance, Dr. Lloyd has made major breakthroughs in deciphering the codes of fireflies throughout North America. The pattern of a species is distinguished not only by the rate of flashes or flickering, but also by the intensity with which the flashes increase or decrease, he said. He gives credit to Frank McDermott, a DuPont chemist, who in the first half of the century cracked many theories of firefly behavior "long before anyone was thinking of
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