Glow-worms and fireflies belong to a family of beetles called the Lampyridae. In Britain there are just two native species- the common glow-worm and the lesser glow-worm. The latter, however, is very rare and confined as a Britain species to a few small, elusive colonies in the southern counties of England. The glow-worm derives its name from the remarkable ability to emit light, a characteristic shared by all members of the Lampyridae, and from the larviform (or worm-like) appearance of the wingless female. The male is a more typical beetle, being fully winged and able to fly. The female is larger than the male, often nearly twice his size.
The function of the glow-worm's light is to attract the mates. As dusk falls, the wingless females only need to sit in the grass and low vegetation,switch on their lights and turn their bodies so that their ''lamps'' are visible to the male flying above. Male glow-worms have much larger eyes than the females and they quickly fly towards the light, so that a glowing female soon attracts a mate. After mating there's no need for light, the female generally douses it and gets on with the business of egg laying.
The beetles are usually found on grassy slopes, verges and hedge banks,and in open grassland especially in chalky and limestone areas. They are mainly nocturnal, the flying males sometimes coming to street and house lights.
The life cycle may take one, two or even three years.