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Firefly research

Firefly ------------------------------------------------------------------------

FAMILY Lampyridae

SPECIES Photinus pyralis

PHYSICAL Best known by their ability to produce light signals from their abdomens at night, fireflies are a type of beetle with a covered head, long black to brown wings with yellow or orange accents. Three-quarters of an inch long. Different species can be recognized by different lengths and rhythms of their flashes.

RANGE P. pyralis is the most common firefly species in the U.S. and is harvested commercially by the biochemical industry.

IN GEORGIA Throughout.

FEEDING Adult and larval fireflies are predacious carnivores and feed on insects, soft-bodied larvae, snails, and each other.

HABITAT Larvae are found on the ground under bark and in moist, wet places. Adults can be found in meadows, woodland edges, and close to streams.

REPRODUCTION Larvae burrow in the soil to overwinter. They emerge in spring and pupate after two and a half weeks. Adults emerge and the males fly about signaling to females on the ground. They mate and the female lays eggs in the soil which hatch four weeks later.

The Signal Of The Firefly

What memory of childhood is as sweet as the collection of fireflies on a warm summer night? All across America, the excited shouts of children capturing lightening bugs in their jars marks the beginning of curiosity at this miracle of nature. Isn't there always one child who smashes the insect on his face to terrorize his friends as some glowing cyclops?

Fireflies, which are beetles, have a unique position among insects because they can flash their lights on and off at will, whereas other luminescent insects can only glow continuously. This cold, yellow greenish light, controlled by the central nervous system of the insect, is produced in the abdomen by oxidizing a complex organic compound, luciferin, by the use of an enzyme luciferase, in the presence of oxygen, magnesium and adenosine triphosphate. The light emitting organs consist of three layers. The innermost layer acts as a reflector as it is a protoplasm of cells packed full of small uric-acid salt crystals which have surfaces that reflect light outward. The middle layer contains the light cells, which are nerve-connected tracheae which contain the light producing enzymes. The outer layer is the skin, which lacks pigment and is transparent.

The light the firefly produces has no infrared or ultraviolet rays but it is relatively bright: forty fireflies can produce the same amount of light as bright as a candle.

So what is the use of this unique ability? Apparently, in general the nocturnal males use their lights to attract and find the female. The male flies over an area where he is likely to find a female and gives off the signals of his species. The female sees this and responds from her perch on the ground. After a series of signals and responses, the male finds the female and mates with her. Generally, the female stops signaling after this, but in some species the female continues signaling to males of other species which she lures to her and then eats!

Different species of fireflies can be recognized by the duration and frequency of their flashes. You can watch for the signal pattern different species, of which there are several dozen in the eastern and central United States. Look for differences in the duration of the signal, the interval between signals, the number of flashes in a signal, the distance the beetle flies during the signal, the color of the signal, and the time of day of the signal. (Firefly species that are active at dusk tend to give a yellow light; those active in darkness tend to give a green light.) Each species tends to restrict its activity to certain habitats which it prefers, such as swamps, Woods, stream beds, or open meadows.

The most common species is Photinus pyralis. Starting at dusk, the male of this large firefly seeks a perched female in open fields, cruising for about an hour. Coming on a field of thousands of flashing Photinus pyralis can be an overwhelming sight. The abundance of these bright insects is fortunate because they are the raw material of the biochemical industry's luciferin-luciferase business.

The firefly life cycle is interesting. The firefly overwinters as larvae buried in the soil. Come spring, the larvae emerge and start feeding. Like the adults, larvae are largely nocturnal. (Fireflies, in both larvae and adult stages are carnivores, feeding on other insects, soft-bodied larvae, snails, earthworms, caterpillars and each other.) Some larvae, called "glow worms" by some, have the ability to emit light, but it is a mystery why they do this because they have no mating needs at this time. In early summer, they are ready to pupate and make a small earthen cell for this purpose, which lasts two and a half weeks. 'The adults emerge and fly about at night flashing their signals. They mate and females lay their eggs a few days later. The eggs are laid on or just under the soil, and they take approximately four weeks to hatch. When the larvae emerge from the eggs, they start feeding and continue until fall, when they burrow underground to overwinter.

Copyright 1998 Georgia Wildlife Federation. All rights reserved.

Revised: May 20, 1999

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