Stag beetle facts
Stag beetles are one of the most spectacular insects in the UK. The male’s large jaws look just like the antlers of a stag. They spend most of their life underground as larvae, only emerging for a few weeks in the summer to find a mate and reproduce. Stag beetles and their larvae are quite harmless and are a joy to watch.
As well as reading our stag beetle facts, please help us protect this threatened British species by telling us about where they live near you and by making your garden stag beetle friendly.
stag beetles Habits
Stag beetles spend most of their very long life cycle underground as a larva. This can be anywhere from three to seven years depending on the weather. Periods of very cold weather can extend the process. Once fully grown, the larvae leave the rotting wood they’ve been feeding on to build a large cocoon in the soil where they pupate and finally metamorphose into an adult. Adults spend the winter underground in the soil and usually emerge from mid-May onwards. By the end of August, most of them will have died. They do not survive the winter. During their short adult lives, male stag beetles spend their days sunning themselves to gather strength for the evening’s activities of flying in search of a mate. This is when you’re most likely to spot them.
Do stag beetles bite?
The male stag beetles’ fearsome-looking jaws are actually only used for wrestling other males to win over a female. They aren’t designed to ‘bite’. It is possible for a female stag beetle to pinch if you were to pick one up, but this is quite unlikely and it’s best to leave them be anyway.
Diet
Larvae feed on decaying wood under the ground. Adults can’t feed on solid food – they rely on the fat reserves built up whilst developing as a larva. They can use their feathery tongue to drink from sap runs and fallen soft fruit.
Breeding
Males are often seen flying around at dusk searching for a mate. They will wrestle or fight other males using their enlarged antler-like jaws. Although they can fly, female beetles are most often seen walking around on the ground. Once they’ve mated, females return to the spot where they emerged, if there is enough rotting wood to feed their young, and dig down into the soil to lay their small, round eggs in rotting wood such as log piles, tree stumps and old fence posts.
Predators
Predators such as cats, foxes, crows, kestrels and others tend to strike at the most vulnerable stage in the beetle’s life cycle, when adults are seeking to mate and lay eggs. Though this is largely natural predation, the rise in the numbers of magpies and carrion crows in the last decade may be having an impact on stag beetle populations.
Humans are, unfortunately, a direct threat to stag beetles. Adult beetles are attracted to the warm surfaces of tarmac and pavements, which makes them particularly vulnerable to being crushed by traffic or feet. Stag beetles have a fearsome appearance and sometimes people kill them because they look ‘dangerous’.
Changes in weather patterns are also likely to have an impact on stag beetles. Exceptionally dry or wet weather is likely to substantially affect the larvae. Wet and windy weather can inhibit adult beetles’ flying ability.
Stag beetles are harmless and do not damage living wood or timber. The larvae only feed on decaying wood so please don’t kill them.
Stag beetles: facts about the UK’s largest beetle and where to see it
Flying haphazardly through the air on a balmy summer day, the male stag beetle is in a hurry to find a mate. Find out how he puts his spectacular antler-like jaws to use, why this species needs protection and how you can help.
Largest beetle in Europe: just how big can a stag beetle grow?
One of the most noteworthy things about stag beetles is their size. Male stag beetles measure up to 7.5 centimetres long when their impressive jaws are taken into account, making this species the largest beetle in the UK and in fact the whole of Europe.
How do other contenders measure up?
The size of an adult stag beetle is influenced by the quality and amount of food it had access to as a larva. The smallest males are about four centimetres long. Even so, male stag beetles are usually considerably larger than female ones, which can be as little as three centimetres long.
What do the male stag beetles use their massive mandibles for?
Male stag beetles use their large, antler-like jaws to battle each other for access to females during breeding season, much like a male deer uses its antlers. This is also where the beetle gets its name.
What do stag beetles eat?
Adult stag beetles don’t eat, but they do drink sweet fluids such as tree sap and the liquid from decomposing fruit. They mostly rely on the energy stores they built up as a larva.
Stag beetle larvae feed on dead wood, using their sharp jaws to scrape the fibrous surface for splinters. Wood infested with white rot is a particular favourite as it helps to decompose the wood. The larvae also digest any fungi and other organisms in the wood.
The larvae seem to prefer the wood of oak trees but will also eat other broad-leaved species such as beech, willow, ash, elm, sycamore, lime, hornbeam, horse chestnut, apple, cherry and some garden varieties. They tend to avoid coniferous species such as fir and pine trees.
They may look charismatic, with their large showy jaws, but for most of their life, stag beetles are large white grubs (called larvae), living underground. Often found in tree stumps and in decaying roots, they feed on rotting wood for several years as they grow and develop before finally transforming into an adult beetle.
Adult stag beetles can’t eat; instead, for the few weeks they live, they rely on the fat reserves built up during their larval stage. However, they can use their feathery tongue to take moisture and energy from rotting soft fruit and sap runs.
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.
So, whether you’re in your garden, heading to a National Park, like the New Forest, or living the city life in London, keep an eye out for these astonishing insects!
