Common name: Stag beetles
Number of species: 4
Size Range: 10-66mm
Description:
There are four species of Lucanidae in Britain, all of which feed in decaying wood although one, the blue stag Platycerus caraboides (L.) has not been seen since before 1900 and is presumed extinct in the country. Lucanus cervus (L.), the stag beetle, is the largest (to 66mm) and perhaps the most recognisable beetle in Britain, especially the male which has long extended mandibles (the ‘antlers’ that give the species its name).
Stag beetles are a family of about 1,200 species of beetles in the family Lucanidae, currently classified in four subfamilies.Some species grow to over 12 centimetres (4+1⁄2 inches), but most to about 5 cm (2 in).
The English name is derived from the large and distinctive mandibles found on the males of most species, which resemble the antlers of stags.
A well-known species in much of Europe is Lucanus cervus, referred to in some European countries (including the United Kingdom) as the stag beetle; it is the largest terrestrial insect in Europe. Pliny the Elder noted that Nigidius called the beetle lucanus after the Italian region of Lucania where they were used as amulets. The scientific name of Lucanus cervus adds cervus, deer.
Male stag beetles are known for their oversize mandibles used to wrestle each other for favoured mating sites in a way that parallels the way stags fight over females. Fights may also be over food, such as tree sap and decaying fruits. Despite their often fearsome appearance, they are not normally aggressive to humans. During a battle between the two males, the main objective is to dislodge its opponent’s tarsal claws with its mandible, thus disrupting their balance. Because its mandibles are capable of exceeding its own body size, stag beetles are generally inefficient runners and are very slow, and typically feel the need to fly from one location to another.
Female stag beetles are usually smaller than the males, with smaller mandibles that are much more powerful than the males’. As larvae, females are distinguished by their cream-coloured, fat ovaries visible through the skin around two-thirds of the way down their back.
The larvae feed for several years on rotting wood, growing through three larval stages until eventually pupating inside a pupal cell constructed from surrounding wood pieces and soil particles. In the final larval stage, “L3”, the surviving grubs of larger species, such as Prosopocoilus giraffa, may be the size of a human finger.
In England’s New Forest, it was once believed that the stag beetle, dubbed the “devil’s imp”, was sent to do some evil to the corn crops. The superstition led to stoning the insects on sight, as observed by a writer in the Notes and Queries.Along with rhinoceros beetles, stag beetles are often bought as pets in South Korea and Japan.
Stag beetle facts
Stag beetles are one of the most spectacular insects in the UK. The male’s large jaws look just like the antlers of a stag. They spend most of their life underground as larvae, only emerging for a few weeks in the summer to find a mate and reproduce. Stag beetles and their larvae are quite harmless and are a joy to watch.
A stag beetle’s head and thorax (middle section) are shiny black and their wing cases are chestnut brown.
Male beetles appear to have huge antlers. They are actually over-sized mandibles, used in courtship displays and to wrestle other male beetles. Adult males vary in size from 35mm – 75mm long and tend to be seen flying at dusk in the summer looking for a mate.
Female beetles are smaller at between 30-50mm long, with smaller mandibles. They are often seen on the ground looking for somewhere to lay their eggs.
The beetle most often mistaken for a female stag beetle is the lesser stag beetle. However, lesser stags are black all over with matt wing cases, while female stag beetles have shiny brown wing cases. Lesser stag beetles tend to have a much squarer overall look.
Stag beetles live in woodland edges, hedgerows, traditional orchards, parks and gardens throughout Western Europe including Britain – but not Ireland. Stag beetles are relatively widespread in southern England and live in the Severn valley and coastal areas of the southwest. Elsewhere in Britain they are extremely rare or even extinct.
Female stag beetles prefer light soils which are easier to dig down into and lay their eggs. Newly emerging adults also have to dig their way up through the soil to reach the surface, therefore areas like the North and South Downs, which are chalky, have very few stag beetles. They also prefer areas which have the highest average air temperatures and lowest rainfall throughout the year.
Diet
Larvae feed on decaying wood under the ground. Adults can’t feed on solid food – they rely on the fat reserves built up whilst developing as a larva. They can use their feathery tongue to drink from sap runs and fallen soft fruit.
Habits
Stag beetles spend most of their very long life cycle underground as a larva. This can be anywhere from three to seven years depending on the weather. Periods of very cold weather can extend the process. Once fully grown, the larvae leave the rotting wood they’ve been feeding on to build a large cocoon in the soil where they pupate and finally metamorphose into an adult. Adults spend the winter underground in the soil and usually emerge from mid-May onwards. By the end of August, most of them will have died. They do not survive the winter. During their short adult lives, male stag beetles spend their days sunning themselves to gather strength for the evening’s activities of flying in search of a mate. This is when you’re most likely to spot them.
Breeding
Males are often seen flying around at dusk searching for a mate. They will wrestle or fight other males using their enlarged antler-like jaws. Although they can fly, female beetles are most often seen walking around on the ground. Once they’ve mated, females return to the spot where they emerged, if there is enough rotting wood to feed their young, and dig down into the soil to lay their small, round eggs in rotting wood such as log piles, tree stumps and old fence posts.
Predators
Predators such as cats, foxes, crows, kestrels and others tend to strike at the most vulnerable stage in the beetle’s life cycle, when adults are seeking to mate and lay eggs. Though this is largely natural predation, the rise in the numbers of magpies and carrion crows in the last decade may be having an impact on stag beetle populations.
Famous for its fearsome jaws, the stag beetle does not have the bite to match. Look for it in woods, parks and gardens in South East England in summer. Males display their massive jaws to attract females and duel with their rivals.
Conservation status：Protected in the UK under the Wildlife and Countryside Act, 1981. Priority Species under the UK Post-2010 Biodiversity Framework.
About
The stag beetle is the UK’s largest beetle and is found in South East England, particularly in South and West London. It prefers oak woodlands, but can be found in gardens, hedgerows and parks. The larvae depend on old trees and rotting wood to live in and feed on, and can take up to six years to develop before they pupate and turn into adults. The adults have a much shorter lifespan: they emerge in May with the sole purpose of mating, and die in August once the eggs have been laid in a suitable piece of decaying wood. Look for the adults on balmy summer evenings, when the males fly in search of mates. Once the male has found a mate, he displays his famously massive, antler-like jaws to her, and uses them to fight off rival males, in a similar fashion to deer.
How to identify
With their massive antler-like jaws and reddish-brown bodies, male stag beetle are unmistakable. Females look similar to Lesser stag beetles, but are larger, with smaller heads and brown wing cases instead of black ones.
