Stag beetles, belonging to the family Lucanidae, are a fascinating group of insects known for their distinctive mandibles, especially in males. While not particularly colorful, their prominent pincers and strong, elongated bodies make them easily recognizable. The most well-known species is Lucanus cervus, the largest terrestrial insect in Europe, often referred to as the stag beetle in the United Kingdom.
Appearance and Identification
Most stag beetles are black, brownish, or reddish-brown. Male stag beetles usually have enlarged, sometimes astonishing jaws. The antennae are enlarged at the tip or clubbed, with segments that fan open like leaves but that cannot be pressed together tightly into a ball. The jaws of male stag beetles are enlarged, imposing pincers that are used for fighting over females. On some species, they look like antlers (hence the name “stag beetle”). Adult males range from 45 to 60 mm in length, while females are smaller, typically around 30-35 mm. They have a slender, elongated form with a somewhat flattened back, shiny elytra, and black antennae and legs. The male has a wide head. The mandibles are as long as the head and thorax combined. Female elytra are lightly punctate.
Larval Stage
The larvae of stag beetles are whitish, C-shaped grubs that live in rotting wood. The heads are often brownish or black, and they have three pairs of legs. Hidden underground, the grubs grow big and strong by feeding on decaying (rotting) plant material. Stag beetle larvae hatch from eggs laid by females on suitable dead trees. Then eat and grow for several years in dead tree stumps. Eventually, each stag beetle larva will create a cocoon for itself, that can be as large as an orange. Larvae eat rotting wood and the juices associated with it. In some places, stag beetle larvae have been found in deep layers of hardwood mulch used in hiking trails and playgrounds. They pupate for seven to nine months, emerging the following June.
Adult Diet
Adults eat tree sap where it runs after a branch or the bark has been injured. They cannot chew food. Fights may also be over food, such as tree sap and decaying fruits.
Habitat Preferences
Most stag beetles are found on the ground in forests. Others frequent sandy stream banks near driftwood. As with other insects, although they can go almost anywhere by foot or by wing, they tend to be near their food sources and egg-laying places. Stag beetles love log piles and old tree stumps, especially from native species like oak trees. Stag beetles love dry areas that don’t get too much rain, and soft soil for digging. Parks, gardens, hedgerows, orchards, and woodlands are all great habitats for stag beetles! They even make their home in the city of London, in places like Richmond Park and Wimbledon Common. In the UK, you can find them in south and south east England.
Read also: Spider Beetle Identification
Geographical Range
Stag beetles are primarily found in southern and central Europe. In the UK, stag beetles are suffering from habitat loss.
Life Cycle and Reproduction
Like most beetles, stag beetles start life as larvae. For up to six years they look like white grubs, and make their homes in old trees and rotting wood. After surviving all those years as a grub, adult stag beetles live for just four months! They emerge from their larval cocoons in late May, and by the end of August, they die. This is the most important time in a stag beetle’s life, as it’s their chance to produce offspring! Adult males use their jaws to fight rivals and impress potential mates, while females dig deep under dead wood to lay up to 21 precious eggs. Males use their giant jaws to fight for access to females. Mating with the females arriving on the tree. Food and protection for their offspring. But the beetle larvae hatch quickly, and receive no additional care.
Predators and Threats
Several animals, including raccoons and woodpeckers, probe or poke through rotting logs and eat the grubs. Many other animals, including birds, bats, skunks, frogs, eat the adults. In the UK, stag beetles are suffering from habitat loss. Their larvae need dead and decaying wood to survive, and sadly, people have often spent time tidying up woodland floors and removing this precious stag beetle habitat!
Interesting Facts and Folklore
Stag beetles have also been called billywitches, oak-ox, thunder-beetles, and horse-pinchers! In folklore, stag beetles are associated with thunder and lightning storms. Amazingly, yes they can! On warm summer evenings, adult males can be spotted flying through the balmy air in search of mates. The beetles fly upright with their wings out behind them. In England's New Forest, it was once believed that the stag beetle, dubbed the "devil's imp", was sent to do some evil to the corn crops. Pliny the Elder noted that Nigidius called the beetle lucanus after the Italian region of Lucania where they were used as amulets.
Conservation
Stag beetles love log piles and old tree stumps, especially from native species like oak trees. So, if you have any of these habitats in your garden, avoid the temptation to tidy! Stag beetles, and loads of other mini-beasts, would much prefer that you left rotting wood alone.
Read also: The Goldenrod Soldier Beetle
Scientific Classification
- Scientific name: Lucanus cervus
- Family name: Lucanidae
- Classification: Insect
Additional Behaviors
Is attracted to lights at night. Forelegs and spread their jaws. Adults and larvae can be found in large colonies in burrows and rotted out logs. During a battle between two males, a stag beetle's main objective is to dislodge its opponent's tarsal claws with its mandible, thus disrupting their balance. Despite their often fearsome appearance, they are not typically aggressive to humans. Males use their giant jaws to fight for access to females. Mating with the females arriving on the tree. Food and protection for their offspring. But the beetle larvae hatch quickly, and receive no additional care.
Read also: The Diets of Beetles