Male Stag Beetle (Lucanus cervus), in my SE London garden.

Stag Beetle (Lucanus cervus)

The Stag Beetle is largest terrestrial beetle in the UK, but sadly their numbers are in decline. Their status is classified as 'Nationally Scarce". Males can be found up to an impressive size of 75mm and very occasionally even 90mm, although 45-60mm is more usual. These beetles are instantly recognisable due to their size. They are uniformly black in colour with chestnut coloured wing-cases. Females can sometimes have maroon coloured wing-cases. The only species that the females are sometimes confused with is the much smaller Lesser Stag Beetle (Dorcus parallelipipedus) which grows to a maximum length of around 30mm. The larvae of the Stag Beetle is a creamy-white colour with a light brown head and grows to an impressive length of around to 80mm, and sometimes even 110mm.

Female Stag Beetles, Lucanus cervus, are usually considerably larger than even the largest Lesser Stag Beetles, Dorcus parallelipipedus. The female is usually fairly close in body-length to the male, minus the large mandibles. However it's not unknown for very small specimens of Lucanus cervus to turn up occasionally. I have seen adult male Lucanus cervus specimens that were incredibly small, less than 30mm in total length! This unusually small size is probably down to the larvae depleting their food source, and being forced to pupate early. I have a dead female Lucanus cervus in my care that's just 33mm in length.

Stag Beetles spend most of their lives living underground as a larvae. This can be for as long as six years feeding primarily from rotting wood from decaying trees and bushes. Stag Beetles usually emerge as an adult beetle around June. Their lives as an adult beetle are short and most live for just six weeks or less. From the moment they emerge their sole purpose is to find a partner to mate with. 

Like many of our wildlife species the Stag Beetle is thought to be in rapid decline and is now a protected species. It is commonly believed that the main reason for this decline comes from loss of habitat. This is largely due to over managing sites and the 'tidying-up' of dead wood and rotting trees that provide food and home for these magnificent creatures during the larva stage. Another possible reason for their decline is a recent increase in the umber of Magpies and Crows, which both prey on adult Stag Beetles. Domestic cats are also responsible for a huge number of Stag Beetle fatalities.

LINK 1    LINK 2    LINK 3

Male Stag Beetle (Lucanus cervus)

It has often been thought that Stag Beetles eat very little or do not feed at all once in the adult beetle form. In studies Stag Beetles have been observed eating over-ripe fruit, nectar and tree sap that can be drunk rather than eaten. Research has shown that Stag Beetles are attracted to ginger. It has also been observed in the wild that Stag Beetles may on rare occasion feed on snails. One has been filmed lifting up a snail and repeatedly smashing it against the ground. The Stag Beetle was then observed to drink up or eat the liquids that ran from the broken snail shell.  LINK



Male Stag Beetle (Lucanus cervus) at dusk.

Stag beetles usually hide themselves away during the daytime and are usually only seen flying at dusk once the sun has set. The best time to see them in flight is on warm, humid evenings during late May - July from 9pm - 10:30pm. They are clumsy fliers and are usually only seen flying if the conditions are right. Their distinctive silhouette, slow and clumsy flight, and large size makes them easily distinguishable from anything else. It is believed that male Stag Beetles will fly up to 500m looking for a mate. Females tend to fly close to their egg-laying site in the hope of attracting the males attention, and don't often fly more than 20m from that site. Females also release pheromones to attract the males. When Stag Beetles pair up they remain embraced together through the night and well into the next day. Mating can last for up to 24hrs. The male will often guard the female until after she has deposited her eggs in rotting wood.


Male Stag Beetle, found in SE London 15th June 2021

How can you help Stag Beetles? Because Stag Beetle larvae feed entirely on rotting wood, the best way to help them is to provide a log pyramid in your garden with the bottom of the logs buried 50cm beneath the soil. The PTES has provided information and tips on this page:  Helping Stag Beetles

Or you can download their excellent help-sheet here:   Helping Stag Beetles pdf.



Male Stag Beetle (Lucanus cervus)

There are many old myths and folk-stories that surround Stag Beetles. Stag Beetles have also been known as billywitches, oak-ox, thunder-beetles and horse-pinchers.

Because Stag Beetles are often seen in warm, humid, and stormy conditions, in British folklore Stag Beetles were feared as it was believed that they had the power to summon thunder and lightning storms. It was also once believed that Stag Beetles flew around with hot coals in their jaws setting fire to buildings!

In Germany the Stag Beetle was associated with Thor, the 'god of thunder' and there was a myth that if you placed a stag beetle on your head, it could protect you from being struck by lightening !


The female Stag Beetle is similar size in size to the male but lacks the large mandibles. They also have a smaller, slimmer head.

REPORT YOUR STAG BEETLE SIGHTINGS

Due to the increased rarity of Stag Beetles in the UK, the PTES are asking for all Stag Beetle sightings to be recorded using one of these links   LINK   LINK2

It is also believed that Stag Beetles don't seem to be reaching the same size that they once grew to. 

When submitting your sightings it would be helpful to measure your Stag Beetle's total body-length and submit that with your records.


Female Stag Beetle (Lucanus cervus) in deciduous woodland on the SE London / Kent borders.







Male Stag Beetles (Lucanus cervus), found 15th June 2021, SE London.

Male Stag Beetles often wrestle to compete for mating rights with female Stag Beetles. They have incredible grip with the ends of their legs being equipped with miniature grappling hooks. It is usually the larger specimen that successfully throws its opponent off the log using its large mandibles. A video posted on Facebook shows a foreign species of Stag Beetle quickly wrestle and remove a clockwork opponent - LINK




Male Stag Beetles (Lucanus cervus), found 15th June 2021, SE London.

Why do Stag Beetles vary so much in size?  It's usually down to availability and quality of food available. The larvae feed on decaying wood beneath the soil for between 2 - 6 years. The longer they spend feeding and the better the quality of food available, the bigger they grow. However if the food source runs out, decays too far or is of poor quality, from treated wood etc, then the Stag Beetle may be forced to pupate and emerge early. I have seen some incredibly small and preserved specimens of adult Stag Beetle, definitely Lucanus cervus, of around just 20mm in length. Size may also be partially due to genetics which is why males wrestle for mating rights. The bigger, stronger male usually gets the girl. Sometimes there may be no big, tough males around and the female has to settle for the little guy instead.



Male Stag Beetle (Lucanus cervus), found 15th June 2021, SE London.







Female Stag Beetle (Lucanus cervus) in deciduous woodland on the SE London / Kent borders 2015






Female Stag Beetle (Lucanus cervus) found in a residential garden in Erith, SE London. 20th June 2023







Female Stag Beetle (Lucanus cervus) found in a residential garden in Erith, SE London. 20th June 2023







48mm adult female Stag Beetle. Found walking under a roadside hedgerow in Cliffe, Rochester, Kent. 17:45 30th June 2023 







48mm adult female Stag Beetle. Found walking under a roadside hedgerow in Cliffe, Rochester, Kent. 17:45 30th June 2023 







Comparison of the Stag Beetle, on the left, and the Lesser Stag Beetle, on the right.

This image is not quite to scale. There is typically more difference in size between the Stag Beetle and the Lesser Stag Beetle.






Female Lesser Stag Beetle (Dorcus parallelipipedus), found within a large fallen and rotting tree in SE London woodland, 16th July 2021

Lesser Stag Beetle  (Dorcus parallelipipedus)

At first glance the Lesser Stag Beetle looks fairly similar to a female Stag Beetle, although the Lesser Stag Beetle are considerably smaller in size, reaching a maximum length of around 32mm, with 25mm being the usual. Occasionally specimens have been known to reach 40mm. Lesser Stag Beetles also have a flatter appearance when viewed from the side, and can usually be distinguished by their matt black elytra, when compared to the satin chestnut-brown coloured elytra of the larger Stag Beetle. Occasionally Lesser Stag Beetles can also be found in a chestnut brown colour, especially with newly emerged teneral beetles. Any red colouration usually fades to black  very quickly, but can take 1-4 weeks of the beetle emerging. The legs are also longer and more spindly-looking on the Stag Beetle when compared to those of the Lesser Stag Beetle, and the Stag Beetle has larger claws at the end of its legs. The head of the female Stag Beetle is much more narrow than its thorax. However, the width of the Lesser Stag Beetleā€™s head is much closer to that of its thorax. 

Female Lesser Stag Beetles usually exhibit two small raised tubercles in the middle of the upper surface of their head. Some sources claim that these tubercles are always present on female Dorcus parallelipipedus, but as one can see from the female specimens that I've photographed this isn't always the case. I wonder if there could be different sub-species of Dorcus parallelipipedus in the UK?

Both species are found in similar environments of woodland and gardens with large trees and both species also feed off decaying wood and plant matter in larvae form. However, Lesser Stag Beetle larvae usually feed on rotting wood above ground level, whereas the Stag Beetle larvae generally feed on rotting wood below ground level. Adult Lesser Stag Beetles feed mainly on sap but can sometimes be found together with the larvae feeding on rotting wood.

Identifying Stag Beetle and Chafer larvae


Male Lesser Stag Beetle (Dorcus parallelipipedus) found under a rotting log in SE London 9th September 2021







 Female Lesser Stag Beetle, Dorcus parallelipipedus, on the left, and male Lesser Stag Beetle on the right.

Unlike the larger Stag Beetle, Lucanus cervus, the Lesser Stag Beetle, Dorcus parallelipipedus, is not obviously sexually dimorphic. The visual differences between the male and female Lesser Stag Beetlle, Dorcus parallelipipedus, are far more subtle. Male Dorcus parallelipipedus have slightly more robust jaws, which are set slightly further apart, and display a larger tooth on the upper inside surface. The male also has a slightly broader, squarer head. Female Lesser Stag Beetles usually exhibit two small raised tubercles in the middle of the upper surface of their head.




Unusual chestnut-brown coloured 19mm female Lesser Stag Beetle (Dorcus parallelipipedus), found under a rotting log at Pevensey Levels, 18th September 2021.

It's highly likely that this reddish-brown coloured Lesser Stag Beetle is teneral, meaning it has only recently emerged from pupation, and the red colouration usually fades to black within a week, but can occasionally take up to four weeks.





Female Lesser Stag Beetle (Dorcus parallelipipedus)

The Lesser Stag Beetle develops quicker than the larger Stag Beetle, and is usually ready to emerge as an adult beetle after around 1-2 years, but some specimens may take 3 years. Adult beetles then usually live for a further 1-2 years, and sometimes several years, unlike the larger Stag Beetle which only lives for just a few weeks as an adult beetle.





Male Lesser Stag Beetle (Dorcus parallelipipedus)
One of two male specimens found together under a log in Richmond Park, London, 19th October 2020.






Male Lesser Stag Beetle (Dorcus parallelipipedus)
One of several specimens found together under a log in Bexley, SE London, 11th June 2021.






Male Lesser Stag Beetle (Dorcus parallelipipedus)
One of several specimens found together under a log in Bexley, SE London, 11th June 2021.