A male stag beetle clinging to a piece of wood — Stag beetles (*Lucanus cervus*) are the largest beetle not just in the UK but in Europe. The males can measure nearly 8cm long. © Achkin/ Shutterstock.com

Stag beetles: Facts about the UK's largest beetle and where to see it

By Lisa Hendry

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.

Stag beetle populations are declining across much of Europe, but did you know London and the surrounding Thames Valley area are hotspots for this magnificent, rare beetle?

Max Barclay, Senior Curator in Charge of the Museum's beetle collection, says:

'Stag beetles are rare and threatened throughout northern Europe and the populations in the Thames Valley are some of the largest in the world. London is a particular stronghold.

'We're lucky that these beautiful and interesting creatures inhabit our city parks and gardens. We should make these gentle giants welcome and be proud to have them sharing our living spaces.'

A male stag beetle on a tree trunk in front of a house — After decades of population declines, stag beetles (*Lucanus cervus*) are rare in the UK. London is a particular stronghold of the species. © Nature Picture Library/ Alamy Stock Photo

Read on to find out more about this charismatic beetle's lifestyle, impressive stats and why it needs our help.

Stag beetle fast facts

Alternative common names: European stag beetle, greater stag beetle
Scientific name: Lucanus cervus
Length, including mandibles/jaws: males 35-75mm long, females 30-50mm long
Weight: 2-6 grams
Average lifespan: 3-7 years
UK status: Native
UK population: Unknown (you can help scientists find out)
UK conservation status: Partially protected
IUCN Red List category: Near Threatened on the European Red List of Saproxylic Beetles (PDF)

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?

In the UK, the stag beetle beats its next rival for the biggest beetle record by a few centimetres. The great diving beetle (Dytiscus marginalis), a voracious predator that lives in ponds, can reach about three centimetres long. Although it is aquatic, this beetle sometimes leaves the water and flies off to settle in a new pond.

The European rhinoceros beetle (Oryctes nasicornis) can be nearly six centimetres long, although two to four centimetres is more usual. One was discovered in the UK for the first time in 2013, in a Worcestershire garden. A lack of further sightings suggests the individual was an escaped pet or was accidentally imported on a plant from Europe. There is no evidence that a population has established itself in the wild in the UK.

Another contender for the title of Europe's biggest beetle is the great capricorn beetle (Cerambyx cerdo), which has a body length of four to five centimetres, excluding the antennae.