Stag beetle season: Everything you need to know about the 'UK's biggest insect' - and how you can help them

If you’d like to catch a glimpse of one of the UK’s biggest and most awe-inspiring insects, now’s your chance - but they won’t be around for long.

Britain’s stag beetle season is now underway, and people across the southeast of England are now more likely to see the striking, antler-jawed males flapping clumsily around before dusk, or the smaller females pottering about on the ground looking for somewhere to nest. The impressive insects will only live for a few weeks - usually until late July - before they die off, with most of their three to seven-year lifespan spent as larvae underground.

Stag beetles are one of the biggest insects in the UK, and are certainly the largest beetles. The males can reach nearly eight centimetres long. Their big white grubs are also enormous, often reaching up to 11cm, and although you won’t usually see them are actually a gardener’s best friend - always hard at work just below the surface.

Unfortunately, like much of Britain’s wildlife, stag beetles are in trouble. They have disappeared or become extremely rare in most of the country, except the southeast - including South London - and the Severn Valley. Although the species is also native to Europe, the People’s Trust for Endangered Species (PTES) says they are on the conservation red list in many countries, and have gone extinct in Denmark and Latvia.

These wonderful beetles are protected in the UK under the Wildlife and Countryside Act 1981, but are still frequently misunderstood or even feared, the Trust says. Here’s why they are actually helpful to us, as well as how you can help them thrive in your garden:

How do stag beetles help your garden?

Stag beetles spend most of their life as larvae - big white grubs - hidden from sight. Eggs are laid in dead and decaying wood, and the larvae will grow up there, a process which takes years. They actually eat this rotting wood, breaking it down and returning nutrients to your soil. This makes it more fertile and easier for your plants to grow.

On top of that, stag beetles help prop up the wider ecosystem. As they burrow through wood, the larvae create passages that other beneficial insects and fungi rely on. The extra fatty grubs are also a nutritious food source for larger wildlife who manage to find them, including a number of birds, badgers, and even foxes.

Are they dangerous?

Although their large mandibles can certainly reach an impressive size, stag beetles are not dangerous to humans. They largely just use them to attract mates, or to wrestle other beetles.

According to the Natural History Museum, male stag beetles only have limited mobility in their mandibles - just enough to give you a tiny pinch if you disturb them. The females can actually nip a little bit harder, but they are typically less likely to bite overall - and their bites are not powerful enough to do any damage to a person.

It’s also worth noting that stag beetle larvae will only feed on rotting wood, not live wood or timber. They do not pose any risk to living trees or structures.

How can you help them in your garden?

One of the driving factors behind the stag beetle’s decline is the disappearance of the decaying wood their grubs need to grow - often caused by the loss of hedgerows, or the over-tidying of parks, woodlands and gardens.

If you’d like to make your garden more stag beetle friendly, you can try building a ‘log pyramid’ - a dead wood habitat of your own, made from fallen or cut tree branches, spare firewood, or old off-cuts. You can bury pieces of broadleaf wood upright in the soil, preferably with at least 50cm below the ground and some left sticking up as well - leaving a little space in between the logs. PTES have more detailed instructions available here.

Male stag beetles can frequently be found sunning themselves during the day as they gather their strength. Unfortunately, they will often choose footpaths, where they run the risk of being stepped on. You should try to gently move them as short a distance as possible if you see one in danger - avoiding the mandibles.

If you’re digging or removing a dead tree and happen to uncover some stag beetle larvae, they can still be saved. If you can’t leave them where they were, the PTES advises you re-bury the larva in a safe shady place in your garden, with as much of the original rotting wood as possible.

Despite their decline across Europe, South and West London remain a hotspot for stag beetles. If you happen to see one while you’re out and about, you can help the London Wildlife Trust monitor how well the species is doing by reporting your sighting here. The Trust is also interested in sightings of lesser stag beetles. These smaller cousins look similar to female stag beetles, but can be told apart by their matte-black wing case. In true stag beetles, this will be a glossy, deep brown colour.

Amber Allott is NationalWorld’s environment and sustainability specialist, covering all things green - from climate to conservation. If you liked this article you can follow Amber on X (Twitter) here and sign up for the free daily NationalWorld Today newsletter here - with Amber bringing you the UK's most important, pressing, weird and wonderful environmental stories every Tuesday.