Stag beetles are a group of about 1,200 species of beetle in the family Lucanidae. Some species grow to 8 cm (3¼ in), but most are about 5 cm (2 in).
The English name is derived from the large and distinctive mandibles found on the males of most species, which resemble the antlers of stags.
A well-known species in much of Europe is Lucanus cervus, referred to in Britain as "the" stag beetle (it is the largest British terrestrial insect). Pliny the Elder noted that Nigidius called the stag beetle lucanus after the Italian region of Lucania where they were used as amulets. The scientific name of Lucanus cervus is this word, plus cervus, deer.
Male stag beetles use their jaws to wrestle each other for favoured mating sites, but despite their often fearsome appearance they are not normally aggressive to humans. Stag beetles are sometimes used in the Chinese sport of insect fighting.
Female stag beetles are usually smaller than the males, with mandibles in normal proportion for a beetle.
The larvae feed for several years on rotting wood, growing into grubs which in larger species may be as big as a human finger.