Ohio State University Extension Fact Sheet

Ohio State University Extension Fact Sheet


1991 Kenny Road, Columbus, Ohio 43210-1090



William F. Lyon

Common Name Scientific Name
Firefly or Lightning Bug Photuris pyralis (Linn.)

Fireflies or "lightning bugs" are needed in medical research laboratories throughout the world. The firefly contains luciferin and luciferase, two rare chemicals used in research on cancer, multiple sclerosis, cystic fibrosis and heart disease. The ability of these insects to produce cold light (bioluminescence) has led to new flashlights and flares on the market today. Scientists have been unable to produce these chemicals synthetically in spite of the great need.

The Chinese thought these twinkling little creatures came from burning grass. A European legend warned that if a lightning bug flew in the window, someone was going to die.

Aztecs used the term firefly metaphorically, meaning a spark of knowledge in a world of ignorance or darkness. American Indians collected lightning bugs and smeared them as decorations on their faces and chest.

They don't bite, they have no pincers, they don't attack, they don't carry disease, they are not poisonous, they don't even fly very fast.


Fireflies are winged beetles. Adults are 7/16 to 9/16 inch long, elongate and very soft-bodied, with the pronotum extending forward over the head, resulting in the head being largely or entirely concealed when viewed from above. The pronotum is reddish-yellow with a black spot in the center. Brownish-black wing covers have a light yellowish area entirely around them except in front. The luminous lower end of a male firefly's abdomen is yellowish-green, whereas the female has a smaller splotch. It is these "taillight" segments where living light is produced. Eggs secreted in the earth may show a touch of luminescence. Larvae are multi-legged, turtle-like creatures with tiny spots on their underside, softly glowing like view holes in the furnace door. Wingless females and luminescent larvae are often called "glowworms."

Life Cycle and Habits

Females deposit eggs in the earth (damp soil), and in about three weeks young sowbug-like larvae appear. The larva is a voracious predator that eats snails, slugs, cutworms, mites and pollen. They inject strong paralytic and digestive juices into their prey and then suck the dissolved body contents, leaving an empty skin or shell. Larvae live one to two years underground and in late spring build a marble-sized mud house around themselves. They then change to a pupa. In about 10 days, new adult beetles emerge with a lifespan of only a few days to a week. They emerge in early summer and remain active throughout August. When a firefly is under stress such as being caught in a spider's web, its taillight glows brightly. Even the shock of a firecracker or thunder may cause a field of fireflies to flash in unison. Ordinarily, the flashing signal is used to find a mate. The pattern of flashing between sexes is fixed. On a relatively cool night, some species wait 5.5 seconds then emit a single short flash. The warmer the weather, the faster the exchange. Other species may wait one second and then hold the flash for a full second. Some tropical species congregate in large numbers and flash in unison. Usually at dusk, male and female fireflies emerge from the grass. Males fly about 1-1/2 feet above the ground, emitting a single short flash at regular intervals. The flashes are usually male fireflies seeking mates. Males outnumber the females fifty to one. Females climb a blade of grass, flashing when males flash within 10 to 12 feet of the females. Exchanges of signals are repeated to 5 to 10 times until mating occurs. Sometimes females will devour males.

Firefly Importance

The light emitted by fireflies is unique. Nearly 100 percent of the energy is given off as light; in an electric arc light, only 10 percent of the energy is light and the other 90 percent is given off as heat. The taillight contains two rare chemicals, luciferin and luciferase. Luciferin, a heat resistant substrate, is the source of light; luciferase, an enzyme, is the trigger; and oxygen is the fuel. A body chemical, ATP (adenosine triphosphate), converts to energy and causes the luciferin-luciferase mixture to light up. Small internal injections of ATP in the firefly tail cause flashes of light that can be measured quantitatively. As all living cells contain ATP in a rather constant concentration, injection of the firefly's chemicals quickly detects energy problems in human cells (different reaction between normal and cancerous cells). The firefly technique is used to study heart disease, muscular dystrophy, urology, antibiotic testing, waste water treatment, environmental protection and diagnosis of hypothermia in swine-a condition costing the pork industry $200 to $300 million each year. Special electronic detectors, using firefly chemicals, have been placed in spacecrafts to look for earth-life forms in outer space. When as little as one quadrillionth of a gram of ATP enters the rocket's detector, a flash of cold light is given off and the signal is recorded by scientists on earth. Other detectors warn that milk, food or water may be bacteria contaminated.

The Sigma Chemical Co., P.O. Box 14508, St. Louis, Missouri 63172 (telephone 1-800-325-3010), is the largest known buyer of fireflies. They purchase and provide fireflies throughout the world for conducting research in a wide variety of scientific areas.

From May through August, fireflies may be seen flying and are easiest to catch at dusk, about one hour before the sun goes down.

A $75.00 bonus is automatically paid at each 50,000 level above 300,000 fireflies. A catcher turning in 75,000 fireflies would be paid at the rate of one cent each of $750.00 plus a $10.00 bonus at the 25,000 firefly level; a $20.00 bonus at the 50,000 firefly level and a $30.00 bonus at the 75,000 firefly level.

Contact the Sigma Chemical Co. for additional details on joining the club.

All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.

Keith L. Smith, Associate Vice President for Ag. Adm. and Director, OSU Extension.

TDD No. 800-589-8292 (Ohio only) or 614-292-6181

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