Stag Beetle Facts – Benefits Of Stag Beetles In The Garden

By: Bonnie L. Grant, Certified Urban Agriculturist

If you have ever seen a stag beetle, you would remember it. These are large insects with rather threatening looking mandibles. In reality, they pose no threat to humans or pets, but they can be aggressive to each other during mating season. Did I also mention that they are big? Think something along the lines of several inches (7.6 cm.) in length at their largest. These are friendly insects, however, that do the gardener many favors.

Stag Beetle Facts

Some of the largest beetles in this family look like something out of a sci-fi movie. However, they are generous giants with just a couple things on their minds. One is mating and the other is eating rotten vegetation. Let’s take a closer look at stag beetle facts to understand their place in the landscape.

There are more than 85 different species of stag beetles that range across the globe. Some are less than a fraction of an inch (1 cm.) and others grow up to 2 ¼ inches (6 cm.). These aren’t the heavyweight champions of the beetle world, but the males are unmistakable with their ferocious looking jaws.

They use these to battle each other during mating season or if another male walks into their territory. The mandibles are the main stag beetle identification clue. Females are a bit smaller and don’t have huge mandibles. Colors range from black to brown and even a few species with oil like rainbow hues.

Are Stag Beetles Good for Gardens?

The benefits of stag beetle habitats near garden areas are astounding. Stag beetle habitats lean towards woodsy areas but can also be found in your wood pile, compost bin, rotting outdoor structure, garbage bin, and anyplace it can find shelter and food. Its main food is vegetation that is rotting.

Adults may come out at night and hang out near your porch light. The larvae stay hidden in rotting wood stumps and the like. The damper and more rotten the wood, the more the amorous adults like the space.

One benefit of stag beetles is the larval feeding behavior on old wood and the adult’s menu, which includes rotten vegetation that helps clean up the yard.

Stage Beetle Life Cycle

Males locate a nice moist, rotten stump and guard it while they wait for likely females. They joust with competing males to ensure their territory. Stag beetles will often be found in colonies under ground near rotting tree roots or in stumps, although each male will stake out his own turf.

Males mate with several females who lay eggs in the stump. The eggs have a short-term food supply, but larvae eat that up quickly and hatch soon after. The larvae are large and will feed on the wood for several years until they pupate for seven to nine months and finally emerge as adults. Adults only live a few weeks or until they have mated.

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While checking the perimeter fence around McDonald Woods to see if there was any damage to the fence after a windy day, I discovered a large red oak that had lost its foothold in the frozen soil and had toppled over against a white oak. Since the tree was threatening to push the other oak over into the fence, I decided to cut the red oak down to save the white oak and the fence.

When trying to remove a leaning tree, you have to start at the base and work your way to the top as each section falls away. The base of the tree was good and solid, sending a shower of sour-smelling oak shavings flying from the chainsaw. When I got about halfway up the trunk, the saw began spewing dark brown flakes of rotting wood, and the sawing became easier. After a few more cuts, the trunk became mostly hollow and the top of the tree crashed to the ground.

Looking back at one of the middle sections of trunk, where the center was a rich dark brown from the rotting wood, I noticed a thick, white object shaped like the letter “C”.

A closer look showed the object to be a large grub from a beetle. These grubs are similar to the white grubs of Junebugs and Japanese beetles that you find in your gardens and lawns, but much larger. Although the rotten wood was frozen, I was able to split open the log, revealing a whole colony of 30 to 40 beetle grubs about 2 inches long and about a half inch in diameter. Each grub was cradled in a smooth-surfaced cell in the rotted wood. Even at temperatures well bellow freezing, the grubs were able to move enough to show they were alive.

As it turned out, these grubs were the larvae of one of our largest woodland beetles, known as the stag beetle or stag-horn beetle. These beetles are one of the myriad invertebrates active year-round, doing the important work of reducing fallen trees to rich organic soil that will help other trees grow and support the next generation of plants.

These beetles are members of the Coleoptera (beetles) and get their name from the large antlerlike mandibles (jaws) found on the front of the head of the males. The females also have mandibles, but they not as impressive as those of the males. The large mandibles are used for territorial defense and also to protect the beetles from any birds or other animals that might try to eat them. The impressive “antlers” can look threatening to people when they first encounter them however, they are not a serious threat to people and will only give you a pinch if you handle them roughly. It is not uncommon to find the large brown stag beetles around buildings near woodlands at night, when they are sometimes attracted to the lights.

These critters are fascinating, not only because they are social in the larval stage and can take several years to mature, but they can also produce an assortment of sounds that are thought to help with communication between the grubs. The grubs have a striated structure on the leg that allows them to produce sound (called stridulation), kind of like rubbing a spoon on a washboard. If you notice the dark-colored segment that looks distended on the end of the grub, it is the digestive chamber, where the wood the grub consumes is digested with the aid of microorganisms. If you give one of these guys a gentle squeeze, you will notice a stream of liquified, dark brown wood coming from the tail-end of the critter.

One last item of interest about these wood-grubbing dynamos is that they often carry a large population of mites around, clinging to their bodies. When I took a closer look at the grubs, I found dozens of whitish-colored tiny mites attached to each of their legs.

This observation lead me to recall the verse by the Victorian mathematician, Augustus De Morgan:

These mites do neither the beetles nor the grubs any harm they are just along for the ride and probably snacking on any choice fecal pellets deposited by the beetles. If you find yourself sitting on a log out in the woods, you just might be perched above a nest of developing stag beetles.

If there is one species of which the Brussels-Capital Region can be proud, it is arguably the stag beetle (Lucanus cervus). The population of stag beetles present within the Region constitutes without doubt the largest core of the population which extends from Halle to Leuven and is vitally important for the preservation of this species at the local level.

Identification and ecology

The stag beetle is the largest beetle in Europe. Besides the beetle's size, it is the "antlers" of the male which particularly capture the imagination. These antlers are made up of huge mandibles which enable it to defend its territory from other males. They are also used to keep hold of females during mating, and to impress the beetle's natural enemies, including woodpeckers, corvids, owls and cats.

If we wish to manage or restore a population, it is important to know that the stag beetle does not fly well and as such cannot cover long distances. It can be ascertained from literature that the maximum dispersion capacity is 1km for females and 3km for males.

The stage beetle likes warmth and as such appreciates south-facing slopes. For their territory, they need broad pieces of dead wood or large trees at the end of their lives and in contact with the soil, as well as well-drained soil which can easily be dug out. The females dig tunnels in the soil and lay their eggs underground, next to dead wood. The larva feeds on dead wood. The tree species does not seem to be important.

Dispersal and status in the Brussels-Capital Region

Due to the threats of extinction which have affected this species, the stag beetle features in annex II of the Habitat directive (Natura 2000), which grants it a special protection status. Its presence in the Brussels Region has contributed to the selection and demarcation of special protection areas of the Natura 2000 network.

In Flanders, the species has been studied as part of the compiling of the Red List and its status was considered as "endangered" (Thomaes A. and Maes D., 2014).

Evidence suggests that the stag beetle appears to have been commonplace in Brussels and its surrounding areas until the 1960s. (Thomaes et al., 2007). A net decline was observed from the 1970s onwards. One of the possible explanations is the change which occurred in the management of the Sonian forest. In earlier times, when the stag beetle was more widespread, the Sonian forest was partially coppiced and was much more open (particularly by the presence of grasslands and clearcutting). These days, the Sonian forest is much more dense. The last observation in the Brussels portion of the Sonian forest dates from 2004. The relict populations are present in areas which have been annexed by agriculture (wooded strips, etc.) and in gardens. We can conclude that, in Belgium, the stag beetle is not a veritable forest species but rather one living in forest edges and wooded embankments, where the microclimate compensates the lack of dead wood.

At the Brussels-Capital Region level, the "Logis" and "Floréal" areas (of Watermael-Boitsfort) are home to the largest known populations of stag beetle. In particular the old Japanese cherry trees (which are sometimes dead) which line the streets of these neighbourhoods offer them nesting possibilities, as do the old railway sleepers near the school at the Jagersveld, and the embankments and their ancient oaks, including the “Busard”, “Trois Tilleuls” and “Fauconnerie” embankments. A study conducted using the "capture-recapture" method indicates that the local population at Watermael-Boitsfort is made up of at least 200 to 300 beetles, and is stable (personal communication of CAMMAERTS R. quoted in NIJS G. et al. 2013). The map below gives an overview of the square kilometres where the species was observed over the period 2003-2014. From the observations available for the period 2003-2014, it can be ascertained that the species continues to disperse across the entire Watermael-Boitsfort territory up to just beyond the boundaries with neighbouring municipalities. However it is difficult to say for sure whether the species is in better shape or if it is just an observation effect.

In the south west of Uccle, the species was mentioned a dozen times over the period 2007-2010, and subsequently more. A dead beetle was also found in Woluwe-Saint-Pierre, at the boundary of Wezembeek-Oppem. No historical data are available for these 2 municipalities.

Square kilometres in the Brussels-Capital Region where the stag beetle has been observed over the period 2003-2014 Source: Brussels Environment, based on

Like other species of community interest which are present in the Brussels Region, the status of stag beetle populations needs to be monitored, as do the status of conservation and protection measures. An evaluation carried out in 2013 considered that, given the size of populations and the current characteristics of their habitat, the local conservation status of stag beetle populations at Watermael-Boitsfort was favourable. Concerning the populations found at Uccle, the available data were insufficient to draw any conclusions (NIJS G. et al., 2013).

Brussels Environment takes action

There is a management plan proposal for the "Logis" and "Floréal" neighbourhoods where the species has been observed in significant numbers in various areas, among others at the Natura 2000 station (“Trois-Tilleuls” embankment).

As previously indicated, the maximum dispersion capacity is 1 km for females and 3 km for males. Based on this data and given the special protection status enjoyed by the stag beetle as a species listed in Annex II of the Habitats directive, the management objectives in terms of preserving a viable population of stag beetles are not limited to the special conservation area as such. In order to guarantee the preservation of this species, measures which are applicable to the entirety of the "Logis" and "Floréal" neighbourhoods - and beyond - appear indeed to be vital.

In summary, the draft plan contains the following measures:

  • preserve the standing dead wood and trees at the end of their lives in the neighbourhoods (taking into account the safety of inhabitants and traffic), in particular for the dead wood situated in warmer and sunny areas
  • so as to ensure a sufficient supply of trees which would allow stag beetles to nest in the future, it is advisable to plant trees throughout the neighbourhood (indigenous oak, Japanese cherry), sufficiently spaced from each other
  • awareness-raising actions (information sessions in particular) towards the actors concerned
  • for 2 embankments ("Trois Tilleuls" and "Kiekendief"), an open forest structure should be pursued, with lots of dead wood and indigenous oak as the dominant species.

The management of these embankments was taken over by Brussels Environment in early 2015 in the context of a partnership agreement with the owner (Le Logis and Floréal Social Housing Company). The measures outlined above have already been partially implemented over several years by the team of eco-workers: the recovery of embankments, by clearing the forest cover and preserving large pieces of dead wood in the soil, and conserving the trunks of Japanese cherry which are likely to be inhabited by stag beetles. These measures will be spread over several years before the optimal quality of habitats for this species is achieved throughout the areas concerned. The plan will be officially adopted after the official designation of the Special Area for Conservation I of the Natura 2000 network, including the stations which are home to the stag beetle populations.

In addition to this management plan, a study was conducted in areas which could potentially accommodate stag beetle populations, in particular in the Bois de la Cambre and the Sonian forest

Stag beetles take flight, but not for long

Male stag beetle with its striking mouthparts, or mandibles. It is endangered and is the UK's biggest terrestrial beetle. Stag beetles only exists as adults for a few weeks and spend most of their life cycle of 4 to 6 years as developing larvae.

( -- About now, and possibly for the next few weeks only, is the time to see the impressive adult stag beetles in flight in the south of England.

Adults of the UK’s largest and endangered terrestrial beetle, Lucanus cervus, live for only a few weeks and the rest of their life cycle is spent underground as developing larvae for a lengthy 4 to 6 years.

In their brief time as adults, they look for mates and desperately search for dead and decaying wood to lay their eggs in, a habitat that has become increasingly rare and has caused their numbers to decline dramatically in the last 40 years.

It’s the adult male beetles that have the striking antler-like mouthparts or mandibles. They can look a little scary but they're only used to warn off other males.

The males can grow to 70mm and the females can be as small as 25mm, although the females are the ones who use their smaller mandibles to bite.

The stag beetle is a protected species and only found in a few areas in southern Britain. Some hot spots include the Thames valley, Severn Valley and parts of the south-west coast.

Sightings of the adults may be becoming rarer, however, the Natural History Museum’s Identification and Advisory Service (IAS) has had its first stag beetle enquiries of the year.

‘We get stag beetle enquiries every year, and they are always positive,’ says Beulah Garner, insect expert in the IAS.

‘In May and June, we had 1 or 2 enquiries a week. Generally people are quite aware of them and aware that they are protected so they ask us what to do when they find them.’

People sometimes find stag beetle larvae, which are creamy white and can grow to a huge 80mm.

Beulah explains one recent enquiry. ‘Last week I spoke to a gardener who had found 4 larvae in her woodpile, and they had to be moved as she was having a fence built.

'We advised her that it was okay to ‘relocate them’ using the soil and dead wood litter she found them in, placing them in shallow soil, underneath or very near to a new pile of dead wood or dead tree stump.’

Female stag beetle, with the smaller mandibles

Another common enquiry, Beulah says, comes from people nervous about telling the female stag beetle apart from the lesser stag beetle, Dorcus parallelipepidus, which isn’t endangered. The main way to tell the difference is the colour of the wing cases - the stag beetles’ are a chestnut red colour, although can be almost black, whereas the lesser stag beetles’ are generally black.

Another way that scientists can check the species is by looking at the number of spikes on the middle of the 3 legs on the tibia - stag beetles have 3 spikes and the lesser stag beetle has 1.

The Museum’s bug forum can help you correctly identify a stag beetle. It has experts giving feedback when you post a message and image. You can then record your sightings online in surveys like the Great Stag Hunt. These records will help with monitoring and future conservation of the species.

Beetles are the most diverse group of organisms on the planet, with over 400,000 described species, and they include ladybirds, weevils, dung beetles and more.

The UK has around 4000 species of beetle. Beetles carry out many crucial roles in nature such as recycling dead wood, dung and the bodies of dead animals, as well as pollinating plants.

It’s commonly thought that stag beetle adults fly between May and August. However, some scientists think this may now be shorter between May and July. This may be due to the fact that there are not as many individuals about any more and so they are seen for a shorter period.

Information about historical flight times, such as when and where a stag beetle was caught or seen flying, can come from notes on specimen labels in the Museum’s collections. There are nearly 9 million beetle specimens in the Coleoptera collection and some are hundreds of years old.

Stag beetles need dead and decaying wood to lay their eggs and to feed on, so leave an area of your garden undisturbed with fallen trees, tree stumps or logs that are in contact with the soil (so that the wood remains moist and can decay).

This kind of habitat is good for other wildlife as well, but if you are lucky enough, you may help these magnificent stag beetles move in too.

Garden wildlife identifier: beetles

Discover some of the UK's beetle life with help from our illustrated identification guide.

Published: Wednesday, 27 March, 2019 at 4:47 pm

Tidying the garden often uncovers an interesting selection of beetles that live in lawn edges, compost heaps or lurk under logs, as they’re well adapted to pushing through root thatch and getting into tight spaces.

Most are useful predators of other invertebrates like bugs, aphids, springtails and maggots. They can be picked up carefully between finger and thumb if you want to relocate them to a nature area. Some larger beetles will try to nip with their jaws, but they can’t pierce human skin.

To encourage them and other beneficial insects to take up residence in your garden, be sure to create habitats for them such as dead wood stacks, compost heaps and bug boxes.

Take a look at our garden wildlife identifier for UK beetles, below.

Black clock beetle (Pterostichus madidus)

Slim, shining and with both black- and red-legged colour forms, this is one of our commonest ground beetles. Lacking wings, it’s flightless but runs like the wind. Usually a nocturnal predator, it also nibbles strawberries. Length 14-16 mm.

Blue ground beetle (Leistus spinibarbis)

Rounded thorax and wing-cases are metallic blue in sunlight chestnut legs and broad, flat, reddish jaws. Fast runner, often found in small groups under stones and logs. Length 8-10 mm.

Devil’s coach horse (Ocypus olens)

Matt black, gothic monstrosity with large jaws. Threateningly rears up its tail, scorpion-like, for defence no sting, but exudes smelly liquid from tail tip. Its short wing cases allow flexibility for crawling in tight spaces. Length 20-28 mm.

Rove beetle (Philonthus politus)

The largest family of beetles, this is black with a metallic tinge on short wing cases. Dwelling in manure and compost, it is fast and agile, and eats fly maggots. Flies readily. Length 10-11 mm.

Sun beetle (Amara aenea)

One of the many greenish, brassy or bronze, oval and rather flattened species Amara. Runs fast, especially in sunshine when its metallic glinting body confuses the eye as it zigzags madly over the patio. Length 5.5-6.0 mm.

Broad ground beetle (Abax parallelepipedus)

Large, broad, flat, almost rectangular, shiny black with deeply ridged wing-cases. Flightless, it likes hedge bottoms, log piles, rockeries, damp areas of rough grass. Length 16-19 mm.

Want to spot more garden invertebrates? Why not take a look at more of our wildlife identifiers to ladybird larvae and dragonflies and damselflies.

Many thanks to Chris Shields, for providing the beautiful illustrations used in this feature.

Stag Beetles

What do stag beetles look like?

Baby Stag Beetles are plump, c-shaped, cream coloured grubs, like most of their scarab beetle relatives. But you can tell if the baby scarab you find is a Stag Beetle by looking at its lower back. If it has two dark, hard, oval-shaped pads on its back, it’s most likely a Stag Beetle baby.

Adult Stag Beetles vary in size depending on their species. Some are just under a centimetre in length, others grow to around 6 cm long. You will most likely find them making a home for their babies in rotten logs and trees or underneath layers of moist leaves on the ground.

Male Stag Beetles are easy to recognise because they have a great big jaw, like a pincer. The females can be a little trickier to spot. Many types of Stag Beetle are brown or black, but there are also a few really beautiful species, like the Rainbow Stag Beetle, that are very colourful.

Where are stag beetles found?

There are over 1,200 species of these big-jawed beetles in the world, and maybe even more than 85 different species just in Australia, but even though there are lots of different types of Stag Beetle, many are facing a loss of habitat that is threatening their survival.

The Broad-toothed Stag Beetle, which is found in south-eastern Tasmania, is an endangered species.

  1. Most adult Stag Beetle species don’t eat much – just a very rare treat of nectar, sap or young tree shoots. Many types of Stag Beetle don’t eat anything at all once they hatch as adults.
  2. Some male Stag Beetles can live for two summer seasons.

Stag Beetles

There are over 1,200 species of these big-jawed beetles in the world, and maybe even more than 85 different species just in Australia, but even though there are lots of different types of Stag Beetle, many are facing a loss of habitat that is threatening their survival.

Stag Beetles love to live in damp woodland areas with lots of leaves and rotting wood on the ground, but unfortunately, these are also the kinds of areas that humans like to clear for houses, farming or to use for logging.

Male Stag Beetles are easy to recognise because they have a great big jaw, like a pincer. The females can be a little trickier to spot. Many types of Stag Beetle are brown or black, but there are also a few really beautiful species, like the Rainbow Stag Beetle, that are very colourful.

The Stag Beetle is a great friend to humans, playing a really important role in ridding forests and our gardens of rotting leaves, fruits and wood.

Baby Stag Beetles are plump, c-shaped, cream-coloured grubs, like most of their scarab beetle relatives. But you can tell if the baby scarab you find is a Stag Beetle by looking at its lower back. If it has two dark, hard, oval-shaped pads on its back, it’s most likely a Stag Beetle baby.

Adult Stag Beetles vary in size depending on their species. Some are just under a centimetre in length, others grow to around 6 cm long. You will most likely find them making a home for their babies in rotten logs and trees or underneath layers of moist leaves on the ground.

Stag Beetles’ jaws can be big and imposing, but they are also really fascinating. They are not at all like human jaws that chew up and down, instead they move sideways. Even more interesting, their jaws are not used for chewing. In fact, most adult Stag Beetle species don’t eat much – just a very rare treat of nectar, sap or young tree shoots. Many types of Stag Beetle don’t eat anything at all once they hatch as adults.

So, what are their big jaws for? Male Stag Beetles use them to wrestle with other male Stag Beetles, especially when a female is nearby or they have stepped into someone else’s territory. It’s how the beetle got its name they use their jaws like a male Red Deer, or stag, uses its antlers to show off and fight.

Stag Beetles love:

  • Thick, damp layers of leaves and organic material left on the ground.
  • Rotting logs and fungus.
  • A little sap or nectar from time to time.

But they don’t like:

  • People or fires destroying their habitat.
  • Other Stag Beetle stepping on their turf.
  • Being moved away from their territory.

Be a Buddy to Stag Beetles

  • Leave a Stag Beetle where it is if you find one in the wild or your backyard. Some Australian Stag Beetles are very rare so it is important that we leave them to breed in their chosen habitat.
  • Plant a few local deciduous trees in your garden. Stag Beetles love the leaf litter created each autumn, especially by trees like Red Cedars and Illawarra Flame trees. The deeper the layers of leaves, the happier Stag Beetles will be.
  • Leave rotting trees or branches on the ground, or place a few hollow rotting logs near a pond or water source in your yard. These make fantastic places for Stag Beetles babies to grow. In return they will help you by eating all of the rotten wood and turning it into great fertilizer for your soil.

  • Using firewood or wood products that come from old growth forests. Old growth forests provide the perfect habitat for some of our most threatened species of Stag Beetle.
  • Getting a pinch. The large jaws of some Stag Beetles aren’t just for fighting: they can also give humans a painful pinch if the beetle feels scared. Although they are not normally aggressive towards humans, it is best to approach these beetles with a little caution.
  • Disturbing Stag Beetle grubs. Stag beetles stay in their larval stage (as grubs) for two or three years. This time is spent collecting all of the energy the beetle needs to grow into an adult and storing all of the energy that it will need for its whole adult life too. That’s a whole lot of eating and storing for a little grub to do.

Don’t be surprised if Stag Beetles:

  • Are hard to find, even with the perfect habitat in your backyard. Stag Beetles prefer to live in woodland habitats that haven’t been damaged by people or forest fires for over fifty years. If you do find one in your yard, it is a pretty special visitor to have.
  • Don’t fly away. Some Stag Beetles can’t fly even though they have wings. Over time, some species have evolved so that their wings are fused closed over their bodies. Other species that live in tropical areas find it hard to fly when it gets too cold. If you find a Stag Beetle that doesn’t fly, it’s all the more reason to protect it because many of the threatened Australian species are the ones that have lost the ability to fly.

A few more Stag Beetle facts

  • Some male Stag Beetles can live for two summer seasons.
  • As part of the International Year of Biodiversity, the City of London ran a competition to design luxury ‘hotels’ for endangered insects, such as Stag Beetles, to be built in its public parks and gardens.
  • It is illegal to collect or remove some species of Australian Stag Beetle from the wild because they are so rare. The Broad-toothed Stag Beetle, which is found in south-eastern Tasmania, is an endangered species.
  • Stag Beetles are nocturnal and they sometimes become attracted to bright outside lights, especially on warm nights.

Not all species of Stag Beetles are threatened, and there are some you can even keep as pets. If you are interested in a Stag Beetle pet, do not collect one from the wild buy one from a reputable pet store and always check which species are protected first. Then you know you are not illegally buying a threatened species.

Watch the video: MB-TV: Keeping Rainbow Stag Beetles

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