Lampyridae

The Lampyridae are a family of insects in the beetle order Coleoptera with over 2,000 described species. They are soft-bodied beetles that are commonly called fireflies or lightning bugs for their conspicuous use of bioluminescence during twilight to attract mates or prey. Fireflies produce a 'cold light', with no infrared or ultraviolet frequencies. This chemically produced light from the lower abdomen may be yellow, green, or pale red, with wavelengths from 510 to 670 nanometers. Some species such as the dimly glowing 'blue ghost' of the Eastern US are commonly thought to emit blue light (<490 nanometers), though this is a false perception of their truly green emission light due to the Purkinje effect. Fireflies are found in temperate and tropical climates. Many are found in marshes or in wet, wooded areas where their larvae have abundant sources of food. Some species are called 'glowworms' in Eurasia and elsewhere. While all known fireflies glow, only some adults produce light and the location of the light organ varies among species and between sexes of the same species. The form of the insect which emits light varies from species to species (for example, in the glow worm found in the UK, Lampyris noctiluca, it is the female that is most easily noticed.). In the Americas, 'glow worm' also refers to the closely related family Phengodidae. In New Zealand and Australia the term 'glow worm' is in use for the luminescent larvae of the fungus gnat Arachnocampa. In many species of fireflies, both male and female fireflies have the ability to fly, but in some species, the females are flightless. Fireflies have a large amount of variation in their general appearance, with differences in color, shape, size, and features such as antennae. Adults can differ drastically in size depending on the species, with the largest being up to an inch long. Although the females of some species are similar in appearance to males, larviform females are found in many firefly species. These females can often be distinguished from the larvae only because the adults have compound eyes, although the latter are much smaller than those of their males and often highly regressed. The most commonly known fireflies are nocturnal, although numerous species are diurnal. Most diurnal species are not luminescent; however, some species that remain in shadowy areas may produce light. A few days after mating, a female lays her fertilized eggs on or just below the surface of the ground. The eggs hatch three to four weeks later, and the larvae feed until the end of the summer. The larvae are commonly called glowworms (not to be confused with the distinct beetle family Phengodidae or the fly genus Arachnocampa). Lampyrid larvae have simple eyes. The term glowworm is also used for both adults and larvae of species such as Lampyris noctiluca, the common European glowworm, in which only the nonflying adult females glow brightly and the flying males glow only weakly and intermittently. Fireflies hibernate over winter during the larval stage, some species for several years. Some do this by burrowing underground, while others find places on or under the bark of trees. They emerge in the spring. After several weeks of feeding on other insects, snails, and worms, they pupate for 1.0 to 2.5 weeks and emerge as adults. The larvae of most species are specialized predators and feed on other larvae, terrestrial snails, and slugs. Some are so specialized that they have grooved mandibles that deliver digestive fluids directly to their prey. Adult diet varies: some are predatory, while others feed on plant pollen or nectar. Some, like the European glow-worm beetle, Lampyris noctiluca, have no mouth. Most fireflies are distasteful to many vertebrate predators. This is due at least in part to a group of steroid pyrones known as lucibufagins, which are similar to cardiotonic bufadienolides found in some poisonous toads. Light production in fireflies is due to a type of chemical reaction called bioluminescence. This process occurs in specialized light-emitting organs, usually on a firefly's lower abdomen. The enzyme luciferase acts on the luciferin, in the presence of magnesium ions, ATP, and oxygen to produce light. Gene coding for these substances has been inserted into many different organisms (see Luciferase – Applications). The genetics of firefly bioluminescence, focusing on luciferase, has been reviewed by John Day. Firefly luciferase is used in forensics, and the enzyme has medical uses – in particular, for detecting the presence of ATP or magnesium.All fireflies glow as larvae. In lampyrid larvae, bioluminescence serves a function that is different from that served in adults. It appears to be a warning signal to predators, since many firefly larvae contain chemicals that are distasteful or toxic. Photic emission in the adult beetle was originally thought to be used for similar warning purposes, but it is now understood that its primary purpose is in mate selection. It has been shown that early larval bioluminescence was adopted in adult fireflies, and was repeatedly gained and lost before becoming fixed and retained as a mechanism of sexual communication in many species. Adult lampyrids have a variety of ways to communicate with mates in courtships: steady glows, flashing, and the use of chemical signals unrelated to photic systems. Chemical signals, or pheromones, are the ancestral form of sexual communication; this pre-dates the evolution of flash signaling in the lineage, and is retained today in diurnally-active species. Signals, whether photic or chemical, allow fireflies to identify mates of their own species. Flash signaling characteristics include differences in duration, timing, color, and repetition, and vary interspecifically and geographically. When flash signals are not sufficiently distinguished between species in a population, sexual selection encourages divergence of signaling patterns.