Stag Beetles are arguably the most spectacular of Britain’s insects. The male, at 35mm – 75mm long, is the largest of our beetles and possesses ferocious-looking antler-shaped jaws. Stag beetles can be intimidating to encounter in the garden, buzzing inelegantly towards you of a summer’s evening. Yet, despite their fearsome appearance, they are completely harmless and play a valuable role in our garden eco systems. Sadly, they are a globally threatened species and numbers in Britain are in decline. Fran Sconce, of the Royal Entomological Society, explains more about these beautiful beetles, why they are endangered and what we can do to encourage their presence in our gardens.
Unfortunately due to overly-tidied domestic gardens stag beetle numbers are in decline
Beetles represent the largest of our insect orders. There are around 1,500 species of stag beetle globally. Four species are found in the UK. These include Lucanus cervus, the stag beetle, with which we are most familiar, and the lesser stag seetle, Dorcus parallelipipedus. Stag beetles belong to the taxonomic family Lucanidae, within the order Coleoptera (beetles) meaning sheath wings. The forewings, or ‘elytra’, are hardened and provide a protective cover for the hindwings, which are used for flight. They also serve as armour in beetle battles!
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The males have an additional protection in the form of large jaws or mandibles that are shaped like male stag deer antlers. The scientific Latin name ‘lucanus’ derives from the Lucania region of Italy where beetle shaped amulets were worn in Roman times. The name ‘cervus’, the Latin word for deer, was inspired by the male stag beetles themselves. More references to beetles occur later in the Middle Ages when, in European folklore, the stag beetle was believed to be a creature of the devil that could fly with live embers in its jaws and set the roofs of houses alight!
They spend 3-7 years underground during a long larval stage
The male jaws are primarily ornamental; the muscles responsible for their movement are too weak to exert the force required for a bite. Their purpose, instead, lies in courtship - to help the male compete for females and intimidate would-be rivals. Occasionally, two males will ‘lock-horns’ and engage in combat and, much like rutting deer, will wrestle for mating supremacy.
After mating, the female, which is smaller in size than the male and has smaller mandibles, will fly off in search of a suitable place to lay her eggs, usually in and around the soil of rotting wood, tree stumps and log piles. These beetles prefer to dig in soft, warmer soils which may explain their proliferation in the parks and wooded areas of South-East England and London, rather than the harder chalk soils of the North and South Downs or cooler, northerly climates.
They eat no solid food during their short adult life
The eggs hatch 2-3 weeks later into cream-coloured, ‘c-shaped’ larvae with orange heads and jointed legs. The larvae are ‘Saproxylic’ meaning they are dependent on dead or decaying wood. They grow up to 110mm long over a 3-7 year period. Yes, you read that correctly; they spend 3-7 years underground and it is during this long larval stage that the beetle accumulates the fat reserves it needs for its pupal and adult life stages. The adult beetles may feed on tree sap but generally they eat no solid food during their short adult life. The female lives only for about a month after emerging from the soil when she quickly begins to search for a mate, and dies soon after laying her eggs.
The beetles undergo a complete metamorphosis to transform from larvae to adults. They pupate for up to six weeks in the soil and become beetles in the early winter. Eventually they emerge as adults in the late spring and summer months when it is consistently warm. Both sexes fly quite frequently in July and August and, being crepuscular (emerging in the twilight) you may encounter them buzzing around the in the garden on a warm summer’s evening.
As gardeners, how do we approach these insects beetling about our gardens?
In short… make them welcome. Stag beetles are now a legally protected species in the UK, they are classified as nationally scarce and in decline across Europe. In the past, gardeners have been concerned about stag beetles causing damage to trees, but since they only feed on dead wood, they cause no damage to living trees or plants. They are wonderful recyclers and their larvae aid the decomposition of decaying plant material while active in the soil, including fungi and other micro-organisms. Stag beetles play an important role in the biodiversity of garden wildlife and they are themselves predated upon by small mammals, reptiles and birds. If you happen to find larvae in the soil while digging or planting, take care not to damage them and ensure you cover them up again.
Unfortunately, due to modern tree management, overly-tidied domestic gardens and decreasing wildlife habitats, stag beetle numbers are in decline. Alterations in our weather patterns due to climate change and associated periods of extended rain or high temperatures are also negatively impacting their numbers. There is evidence that stag beetles are moving to locations they would previously have found too cold, for example in recent years, they have been recorded in greater numbers in the Midlands.
Gardeners should celebrate the presence of these beautiful beetles and provide habitats for them in and around the garden. Consider creating log piles of deciduous wood, particularly from oak or fruit trees. Additionally, leaving tree stumps in place and creating piles of branches or tree debris collected throughout the season, will provide suitable habitats. Away from the domestic garden, if you find one in a park or on pavements or roads, move it carefully to safety away from footfall or vehicles.
So, if a stag beetle comes flying towards you on a warm summer evening, there’s no need to be scared, count it as a blessing and remember they are endangered and in need of our protection.
Top fun facts
• The rainbow stag beetle Phalacrognathus muelleri lives in the rainforest of the wet tropics of Queensland Australia, unlike our native species it has a strikingly beautiful iridescent coloured body.
• Stag beetles are kept as pets in Japan, ‘kuwagata mushi’ can be bought in pet shops and kept for several years at home in terraria.
Further information on stag beetles can be found at People’s Trust for Endangered Species, you can map your log pile and take part in the Great Stag Hunt
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