What do stag beetles eat? And other staggering facts

Male stag beetle
Male stag beetles are instantly recognisable thanks to their huge jaws – they look like deer antlers. (Photo: Orchi/Wikimedia Commons.)

Meet the stag beetle (Lucanus cervus). It’s the minibeast that’s not so mini – stag beetles can be up to 8cm long and have huge mouthparts (mandibles) that look like the antlers of a stag. These impressive beetles are shiny with brown wing cases.

They emerge from their winter hideouts in May so now’s the time to look out for them. We’ve put together some staggering facts about our largest land-living insect.

What do stag beetles eat?

The larvae (grubs) chomp on decaying wood under the ground, but once they’re adults it’s thought that they don’t eat anything! They do drink sap, the sticky stuff that comes out of trees, as well as juice from rotting fruit.

Male stag beetle
The male stag beetle's huge jaws are used for fighting, not eating. (Photo: Alisa24/iStockphoto.)

Where do stag beetles live?

Mainly in south and south-east England. You’re not really going to come across one if you live in the north – sorry! They make their home in woods, especially oak woods, as well as in parks and gardens.

How long is the stag beetle lifespan?

The eggs hatch in a few weeks but the larval stage can last for an incredible six years! During this time, it grows to adult insect size, shedding its skin five times in the process. It then makes a cocoon (protective case) in the soil and develops into an adult beetle inside, usually in the autumn. After emerging from the cocoon, it hides underground until spring. The adult only survives for a few months – usually from May to August. During this time it will mate and the female will lay her eggs.

Stag beetle larvae
This big beetle has big babies – the larvae can grow up to 11cm long! (Photo: JUN2/iStockphoto.)

What’s the difference between male and female stag beetles?

The female is smaller than the male – they grow up to around 5cm long. She has smaller mouthparts but they’re stronger than the males’. The male mostly uses his huge mandibles to fight with other males, and to show off to lady stag beetles!

Female stag beetle
The female stag beetle has much smaller mouthparts than the male. (Photo: Henrik L/iStockphoto.)

Can stag beetles fly?

Yes – you’re most likely to see male stag beetles flying around at dusk looking for females to mate with. They look quite strange as they fly upright with their wings held behind them.

Are stag beetles poisonous?

No, they’re not poisonous. And their huge jaws may look scary but they’re unlikely to bite. Still, it’s best to look but not touch, unless you see one that’s in danger of being squashed ¬– they do like to sun themselves on tarmac! If you see one in harm’s way, pick it up carefully and move it to a safe place.

Are stag beetles endangered?

Yes, numbers are going down and it’s classed as a protected species. This is mainly because of loss of its woodland habitat and because people like to tidy up parks and gardens so there’s less rotting wood for the larvae to feed on. If you live in a stag beetle area, you can help by making a small log pile in your garden. You just need to collect a few chunky logs from broadleaved trees.

Are there different species of stag beetle?

Yes, we have two other species that belong to the stag beetle family in the UK.

The lesser stag beetle (Dorcus parallelipipedus) is smaller - it's around 3cm long. It has smaller jaws and is matt black all over.

Lesser stag beetle
Lesser stag beetles are often confused with female stag beetles. (Photo: Dawn Monrose/WTML.)

The rhinoceros beetle (Sinodendron cylindricum) is also known as the horned stag beetle. It measures up to 2cm long and has a tiny rhino-like horn on its head.

Rhinoceros beetle
The rhinoceros beetle has a tiny horn on its head! (Photo: Sandy Rae/Wikimedia Commons.)

Have you spotted a stag beetle? Share your exciting discoveries with us using #NatureDetectives. And if there’s no chance of finding a stag beetle where you live, don’t worry – you can turn yourself into one with our stag beetle mask!

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