Some Frequently Asked Questions about the Stag Beetle:

WHAT IS THE STAG BEETLE'S SCIENTIFIC NAME?

The scientific name for the Stag Beetle isĀ Lucanus cervus.

HOW CAN YOU TELL THE DIFFERENCE BETWEEN A MALE AND FEMALE STAG BEETLE?

The main difference between the male and female Stag Beetle is their mandibles, or jaws. Male beetles have the large, over-developed antler-like mandibles which give the beetle its name. These mandibles are used during fighting and mating. Females have much smaller mandibles. In the images below, the male can be seen on the left, while the female is on the right.

HOW BIG ARE STAG BEETLES?

Stag Beetles vary quite a bit in size. As a general rule males are larger than females, but there is overlap in their size range. On average males can grow to anywhere from approximately 35mm-75mm long, and females can reach anywhere between 30-50mm.

Whatever size the beetle is when it emerges is the size it will remain for the rest of its (rather short) life – a small beetle isn’t going to grow into a bigger beetle with time.

If you’ve found what appears to be a particularly small Stag Beetle, it may be that it’s not actually a Stag Beetle at all, but is in fact a Lesser Stag Beetle (Dorcus parallelopipidus). These look very similar to a female Stag Beetle (neither male or female Lesser Stag Beetles have the large mandibles that a male Stag Beetle does), but are generally a bit smaller and a bit flatter. Whilst Stag Beetles have slightly chestnut-brown wing cases, the Lesser is darker in colour – almost black all over.

Lesser Stag Beetle

HOW LONG DO STAG BEETLES LIVE FOR?

In their adult form, the beetles only live for a few months at the very most. Females generally outlive males by a small amount, but even they only have an average lifespan of around 12 weeks.

As with all insects, the adult stage is only a small part of the life-cycle of the Stag Beetle though. Before emerging as a fully formed beetle, they have to go through several other stages. Starting off as an egg, they then hatch into a larva, before pupating and eventually developing into an adult beetle. The entirety of this process can take up to around 6 years.

HOW COMMON ARE STAG BEETLES?

Very rare – Stag Beetles are an endangered species. They are only present across a small part of the UK, and recent surveys suggest that their range is shrinking further.

They are listed as a Priority Species under the UK Post-2010 Biodiversity Framework, as well as a Priority Species on the UK Biodiversity Action Plan (1995). They are also afforded limited protection by the Wildlife and Countryside Act 1981 and are on the IUCN’s European Red List.

WHAT DO STAG BEETLES EAT?

Adult beetles don’t generally eat much at all – they can’t eat anything solid, but can occasionally be found feeding on fruit juice or tree sap. The fat reserves that they live off are built up during their larval stage, when they feed off rotting wood.

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