They're the UK's largest and possibly most magnificent beetle.

Measuring up to 7cm, male stag beetles, with their characteristic mix of black and chestnut brown bodies, are quickly recognisable.

They also sport impressive antler-like mouthparts, which they use to joust like knights, locking horns as they attempt to knock a competitor off a log or tree to earn the rights to mate with a female.

But despite their large size, beautiful colours and fascinating behaviour, many of us have never seen the UK's spectacular stag beetle.

One of the UK's most iconic insects is under threat and becoming increasingly rare to find, and that’s a real shame.

England is a stronghold for the beetle, which is why it is so important for us to look after it

So the People’s Trust for Endangered Species (PTES) is encouraging anyone who has seen a stag beetle to join their Great Stag Hunt Survey and record it.

“Reporting sightings helps us to keep an eye on how the beetle is faring, and we can learn so much about the species by observing their behaviour,” said Laura Bower, the charity's conservation officer.

So far this year there have been over 1,200 stag beetle sightings recorded, a number that will hopefully continue to grow over the summer. It’s vitally important that all sightings are reported.

“The actual numbers of stag beetles are very hard to assess, but do appear to have stabilised in the UK, although declines are still going on across Europe.

“England is a stronghold for the beetle, which is why it is so important for us to look after it,” she added.

Life’s too short

A stag beetle’s life-cycle is quite remarkable.

It takes between two and five years for the larvae to develop underground, living solely on decaying wood. The adults emerge in May and June to reproduce.

However, the adult form only survives for a few months above ground; often it’s not long enough to find a mate before the summer ends.

According to Bower, the decline of the stag beetle has been mainly due to habitat loss, as they need dead and decaying wood for their larvae to feed on.

“As they have a long life-cycle, they are vulnerable to disturbance. For instance when dead trees are removed, this can devastate a local population,” she told BBC Earth.

And while the young can be so easily disturbed, the short-lived adults are vulnerable to magpies, cats, humans and many other predators.

To help them, Bower suggests that we leave dead trees and stumps or build log piles in our garden.

Building the perfect stag sanctuary is a good start and the PTES has some great tips on their website to help you.

There is no other creature here in the UK quite like it

“People are amazed when they discover that such a large, charismatic beetle can be found in their gardens,” she added.

They are easy to recognise and, despite their fierce appearance, are quite harmless to both humans and living wood and timber.

To find out more about the majestic stag beetle, the charity has a comprehensive guide on their website.

“There is no other creature here in the UK quite like it.”

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