Stag beetles

David Chapman / 05 June 2018

Stag beetles are a legally protected endangered species. Find out how gardeners can help provide a suitable habitat for them.



Beetles are not regarded by many as the most exciting form of British wildlife but if you think all beetles are small, black, shapeless, uninteresting critters then maybe it’s time to think again.

We have more than 4,000 species of beetle in the UK. They vary enormously in colour with some being bright red, others are iridescent green, many are black and red whilst some are simply black.

Beetles have adapted to live in a huge range of habitats. We might expect to see beetles on rotting wood but some species have adapted to live underwater whilst others live on beaches. And we must thank beetles for disposing of a huge range of waste matter including dung, fungi, rotting wood, and would you believe that some beetles even bury and subsequently eat dead animals?

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The differences between bugs and beetles

All of this variability begs the question, “What is a beetle?” We always look for simple answers to questions such as this when often they don’t exist but thanks to the ‘beetle drive’ game that most of us must have played at some point in our lives, we all have a pretty good idea about beetle morphology.

In keeping with all insects beetles have six legs, they also have antennae. We might tend to lump bugs and beetles together but they are different because bugs, such as shield bugs and froghoppers, have sucking mouthparts whereas beetles have biting mouthparts. Generally beetles have hind wings, which most can use for flight, but unlike most flying insects their hind wings are hidden under hardened forewings. These hardened forewings, or wing cases, are known as elytra and they give the beetle its shape and colour, so when we look at a ladybird most of what we notice are the elytra.

The stag beetle – the UK’s largest beetle

There aren’t many beetles that can grab the attention and excite the imagination quite like the stag beetle (Lucanus cervus). This is our largest terrestrial beetle, with some males growing up to three inches long, and which is adapted to have huge mouthparts which we liken to a stag’s antlers. These mouthparts are useless for biting but, like a deer stag, the male stag beetle uses these over-sized mandibles for sparring with other males.

Stag beetles aren’t the most colourful of beetles. Their head and thorax are black and their elytra are chestnut, giving them good camouflage in the woodland environment where they live. Only the males have large antler-like mandibles.

Female stag beetles are smaller with much shorter mandibles but don’t let appearances fool you, when it comes to biting the female has more powerful jaws and can inflict quite a nip. The female stag beetle can be confused with the lesser stag beetle (Dorcus parallelipipedus). Lesser stag beetles are more common than stag beetles and are more widely distributed in the UK but their wing cases are matt black rather than chestnut coloured.

Life cycle of the stag beetle

Most of the stag beetle’s life cycle is spent as a grub which feeds on decaying wood, usually underground. Their grubs are white with brown head and legs. These grubs can take between three and seven years to develop sufficiently to form a cocoon and pupate. This is done in the autumn and though the adult will form in this cocoon it won’t emerge until the following summer. Adults live off the fat reserves established as a grub and will only drink to sustain themselves. They emerge from mid-May onwards and all will have died by the end of August.

Adult male stag beetles like to rest and sun themselves during the day. At dusk and during the night they fly in search of a mate. Female stag beetles tend not to fly as much, preferring to walk around to look closely for suitable places to lay eggs and this is where we should be prepared to help by providing better habitat for beetles.

Stag beetle numbers in the UK

Over the years our management of woodland and gardens has had a negative impact on stag beetles to the extent that they are now nationally scarce and simply do not occur across large swathes of their former range. Their grubs depend on being able to find rotting wood and unfortunately we have a tendency to be too ‘tidy’ in our gardening and management of the landscape. Did you know that 700 species of beetle in the UK depend upon rotting wood? So in our gardens we should create log piles for beetles (vertical log piles, with the base of each log buried in the ground, are thought to be good for stag beetles).

In the wider landscape we must change our approach to woodland management and allow fallen trees to remain in situ. Such management practices are now employed by most conservation groups such as the National Trust, Woodland Trust and Wildlife Trusts and in stag beetle strongholds such as Richmond Park, Wimbledon Common, Epping Forest and the New Forest there are stag beetle specific management strategies.

It is clear that the south east of England is the species’ stronghold in the UK but they can also be found in the Severn Valley, parts of Wales and at scattered other locations as far north as Cheshire. It is important if you see stag beetles, especially outside the mentioned hotspots, that you send in your records to the People’s Trust for Endangered Species (ptes.org).

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The opinions expressed are those of the author and are not held by Saga unless specifically stated.

The material is for general information only and does not constitute investment, tax, legal, medical or other form of advice. You should not rely on this information to make (or refrain from making) any decisions. Always obtain independent, professional advice for your own particular situation.