The Mighty Stag Beetle

Sticking with the recurring theme of brilliant British beasts, this week the mighty stag beetle (Lucanus cervus). Being a beetle they are of course an insect and belong to the order Coleoptera (the beetles) which is actually the largest of the insect orders, containing approximately 360,000 species, with more being discovered all the time. There are roughly 4,000 Coleoptera species in Britain but I think it’s pretty fair to say that  L.cervus is certainly one of the most impressive British beetles. They can reach majestic sizes, with the males being larger than the females, attaining lengths of up 75mm and 45mm respectively, however it isn’t just their large size that makes them such a spectacle.

The males have grossly enlarged upper mandibles that look like large antlers, giving them a formidable, prehistoric appearance. It is these antler-like appendages that give them their name and whilst they certainly look threatening they cannot be closed with any great measure of force. Therefore they are not used to hunt, but to wrestle! The males use these appendage to wrestle and compete with one another in hope of impressing a female and gaining the chance to mate. In fact, because of this mouth-part modification, they’re not able to feed on solid food and instead gorge on tree sap. So, if you’re going to get a nasty nip from a stag beetle, it will be from the smaller, but still impressive and very strong, female.

A large female stag beetle, displaying the lack of modified mandibles.


The majority of a stag beetles life is spend as a larvae, which live in rotting wood for up to six years, and once they pupate and emerge as an adult (normally in early May), they only live for a few months. Just long enough to mate and lay the next generation. Like most beetles, especially the larger ones, they are not particularly graceful or quick, and tend to plod along. But if you thought they were cumbersome on ground, they’re even more unsteady in flight. Not only are they heavy but, again like all beetles, they only have one pair of functional wings with the other pair forming a hard protective wing cover, known as the elytra. This results in them being well armoured, but not the best flyers and you can see them coming from a long way away, and if you somehow you miss them, you’ll definitely hear the low pitch hum that accompanies them.

The larvae of a Stag beetle

They’re becoming increasingly rare in the UK due to habitat loss and tend to only be seen in the South. I am lucky enough that last summer we had them in our garden, emerging from the ground and flying around. Just realised, this the second post where I’ve been lucky enough to find an awesome animal in my back garden, I do go out looking for animals I promise, I am just a bit of a jammy so and so. But as an indication as to how rare they are, the majority of the members of my university’s Entomology society, filled with people who spend their lives in search of cool insects, have never been fortunate enough to see a wild stag beetle. It is a shame that these incredible insects are becoming so rare and do not receive the kind of attention that charismatic vertebrates do. There are ways that we can help them, for example, constructing a woodpile in a warm part of the garden for the beetles to lay their eggs in and for the larvae to inhabit. That is actually why we had them in our garden, there was a large rotting, hollow tree stump that contained larvae and it was around this stump that the adults emerged from.

These impressive invertebrates really are a spectacular sight, and it is a shame that they having become so endangered. Thankfully, there are some organisations that are trying to help the stag beetles by constructing suitable habitats for them, both within nature reserves as well as in the wild. So, there is hope for them yet.

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A male stag beetle, with its mighty “antlers”

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