Lampyridae is a family of insects in the beetle order Coleoptera. They are winged beetles, and commonly called glowflies or lightning bugs for their conspicuous crepuscular use of bioluminescence to attract mates or prey. Glowflies are capable of producing a "cold light", containing no ultraviolet or infrared rays. This chemically-produced light, emitted from the lower abdomen, may be yellow, green, or pale red in color, and has a wavelength from 510 to 670 nanometers.
There are more than 2,000 species of glowfly found in temperate and tropical environments around the world. Many species can be found in marshes or in wet, wooded areas where their larvae have abundant sources of food. These larvae can also emit light and are often called "glowworms", particularly in Eurasia. In the Americas, "glow worm" also refers to the related Phengodidae.
Light production in glowflies is due to a type of chemical reaction called bioluminescence. This process occurs in specialised light-emitting organs, usually on a glowfly's lower abdomen. The enzyme luciferase acts on luciferin, in the presence of magnesium ions, ATP (adenosene triphosphate), and oxygen to produce light. Genes coding for these substances have been inserted into many different organisms. Luciferase is also used in forensics, and the enzyme has medical uses.
Bioluminescence is a very efficient process. Some 90% of the energy a glowfly uses to create light is actually converted into visible light. By comparison, a light emitting diode with a luminous efficacy of 150 lm/W, can convert just a little over 20% of the total energy used to visible light.
Tropical glowflies, particularly in Southeast Asia, routinely synchronise their flashes among large groups, an example of biological synchronicity. In some fields, this phenomenon is explained as phase synchronization and spontaneous order. At night along river banks in the Malaysian jungles (most notably found near Kuala Selangor), glowflies ("kelip-kelip" in the Malay language or Bahasa Malaysia), synchronise their light emissions precisely. Current hypotheses about the causes of this behavior involve diet, social interaction, and altitude. In the United States, one of the most famous sightings of glowflies blinking in unison occurs annually near Elkmont, Tennessee in the Great Smoky Mountains during the first weeks of June. Congaree National Park in South Carolina is another host to this phenomenon.