Stag beetles are distinctive insects, immediately recognizable by the male’s enlarged mandibles, which resemble deer antlers and give them their common name. Their head and middle section are typically shiny black, contrasting with chestnut-brown wing cases. Males can reach lengths of up to 75mm, while females are generally smaller, measuring between 30-50mm, and possess much smaller mandibles.
Life Stages and Environment
Stag beetles spend most of their lives as larvae, residing underground or within decaying wood. The large, C-shaped white grubs with orange heads feed exclusively on rotting wood, such as logs, tree stumps, and old fence posts. This feeding period lasts three to seven years, depending on environmental factors like temperature and the wood’s nutritional content. As they consume wood, larvae grow up to 110mm.
Once fully grown, larvae leave the decaying wood to construct a cocoon in the soil for pupation. This transformation occurs over several weeks or months. Adult stag beetles usually emerge from mid-May onwards, often after warm summer rains soften the ground, allowing them to burrow to the surface. They are commonly found in woodland edges, hedgerows, traditional orchards, parks, and gardens, especially where dead wood is abundant. Females prefer lighter soils for egg-laying, as they are easier to dig.
Adult Activities
Adult stag beetles have a short lifespan, lasting a few weeks to a couple of months, typically dying by the end of August. During this brief adult phase, their primary purpose is reproduction. Adult beetles do not consume solid food, relying instead on fat reserves accumulated during their larval stage. They can, however, use their feathery tongues to drink sweet fluids like tree sap and liquid from decaying fruit.
Male stag beetles use their antler-like mandibles in courtship displays and combat with other males for mating rights. These contests involve wrestling and attempting to dislodge rivals, often by lifting them. Larger males typically win these fights. Males are frequently observed flying at dusk during summer evenings, searching for females. Females, while capable of flight, are more often seen walking on the ground as they seek suitable egg-laying locations.
Role in Ecosystems
Stag beetles play an important environmental role, particularly through their larvae’s activities. As decomposers, larvae break down dead wood, returning essential nutrients to the soil. This process contributes to nutrient cycling and forest ecosystem health. Their presence can indicate a healthy, biodiverse environment, especially in woodlands and gardens.
Stag beetles also serve as a food source for various animals. Predators include birds (crows, kestrels) and mammals (foxes, badgers, hedgehogs, cats). Magpies are known to prey on adult stag beetles, often leaving characteristic remains. Adult beetles are vulnerable to predation when they emerge to mate and lay eggs.