European stag beetle – Lucanus cervus

Life cycle of a male stag beetle.
Life cycle of the stag beetle. Designed by Maria Fremlin and illustrated by Carim Nahaboo.

Description

The European stag beetle is named after the particular appearance of the male: a big beetle with impressive jaws that look like antlers of a deer. These jaws are a weird creation of evolution, they are used to impress and fight with male competitors. Sometimes they even scare away predators such as woodpeckers and owls.

While the males can be between 4 and 9cm long, females are rather small, around 3 to 4cm. Also, females have much smaller jaws.

Sometimes the female can be confused with other species. Here is described how to distinguish from other species.

The life cycle

Female adults lay eggs next to belowground dead woody materials, on which the larvae will feed. Important is that the wood is moldy and moist, and in direct contact with the soil. In addition, sun exposure is also important, so the soil can warm up sufficiently. For a long time, it was believed that the stag beetle is typical for old oak forests, but larvae have been found in places such as old orchards, parks, roadside trees, railway sleepers and other dead wood in gardens. So you migth wonder why this beetle became so rare. Its prerequisite is habitat continuity: stag beetles are found at places where dead wood was continuously available during the last centuries.

The beetle lives most of its life underground. First it lives one or more years as a blind larva, growing up to 10cm and building up fat. When full grown, its color changes from white to yellowish. Finally, the larva will spin a cocoon and undergo a metamorphosis. In a few weeks, it becomes an adult (it is then called an imago). The adult beetle will wait inside the underground cocoon until next spring to fly out.

Flying male stag beetle in Russia. Picture by Stanislav Shinkarenko.
Flying male stag beetle in Russia. Picture by Stanislav Shinkarenko.

Once an adult, the stag beetle is not able to eat anymore. It is only able to suck up juices from tree wounds or rotten fruit. Male adults only live for a few weeks. Females live a bit longer, up to a couple of months. The mating season starts around June. On warm summer evenings, the males start flying around sunset, whirring around, searching for females. Their bodies are not particularly aerodynamic, so they have an extremely clumsy way of flying. They can only fly in a vertical position, due to their heavy antler-like jaws. Hopefully the males find females to mate with, so the circle of life can start again.