Lampyridae is a family of insects in the beetle order Coleoptera. They are winged beetles, and commonly called fireflies or lightning bugs for their conspicuous crepuscular use of bioluminescence 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.
There are 2,000 species of firefly found in temperate and tropical environments. Many are in marshes or in wet, wooded areas where their larvae have abundant sources of food. These larvae emit light and are often called "Glowworm", in particular, in Eurasia. In the Americas, "glow worm" also refers to the related Phengodidae.
Fireflies, also known as Glowworms, tend to be brown and softbodied, often with the elytra more leathery than in other beetles. Though the females of some species are similar in appearance to males, larviform females are found in many other firefly species. These females can often be distinguished from the larvae only because they have compound eyes. The most commonly-known fireflies are nocturnal, though there are numerous species that are diurnal. Most diurnal species are non-luminescent, though some species that remain in shadowy areas can 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 3–4 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 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 non-flying 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, they pupate for 1 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. One such species is Alecton discoidalis which is found in Cuba. 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.
Most fireflies are quite distasteful and sometimes poisonous to vertebrate predators. This is due at least in part to a group of steroid pyrones known as lucibufagins (LBGs), which are similar to cardiotonic bufadienolides found in some poisonous toads.