Distribution: Southern and central Europe. In Britain, they are found in southern and southeastern areas of England.
Habitat: Broad-leaved woodlands, especially oak, but also parks and gardens where there are hedgerows, tree stumps and logs.
Size: Dark, violet-brown elytra (wing cases) with reddish-brown antlers (female's antlers are much smaller than the male's). Larva is creamy-white.
Life-span: The larva lives 3-5 years. Adults live only between the months of May and August.
Food: Larva eats rotting wood and roots. It is thought that the adult either eats tree sap or nothing at all.
The stag beetle is Britain's largest insect and one of the most well-known of all the beetles. The male is easily recognised because of his mouthparts which have evolved into enormous jaws, resembling the antlers on a stag's head. Despite their fearsome appearance, these antlers are useless for biting, and are used to fight other males. It is the smaller female we need to be wary of - her tiny antlers may look less threatening but they can inflict a sharp nip!
Unfortunately, the stag beetle is now rare in Britain, mainly due to loss of suitable habitat. Read on to find out how you can help >
Stag Beetle Habits
Breeding: Adult male stag beetles emerge in May or June, depending on the weather, followed shortly after by the females. The male has strong wings underneath the wing cases (elytra) and he flies at dusk in search of females. The flight can be rather erratic and the beetle sometimes flies indoors through open windows or doors, attracted by the light - and sometimes he bumps into things and crash lands.
When the male has found a female, he lifts his head, opens his antlers wide and walks around her, showing himself off. If two males are interested in the same female, they will fight each other, using their antlers like a male deer. The stronger of the two turns the other onto his back and the loser retreats. Injuries are rare as the encounter is more of a display of aggression than a dangerous fight.
After mating, the female finds some moist decaying wood in which to lay her eggs. She prefers oak woodlands but where these are scarce she will seek out logs and old tree stumps in parks, gardens and hedgerows. When she has laid her eggs, she dies, and the male does not last much longer.
Each egg hatches into a creamy coloured larva, looking like a fat, wrinkly grub with an orangey-brown head and six stubby legs. It has tough jaws for tearing up and chewing decaying wood. This type of food is not very nourishing, so it takes three to five years before the larva is ready to turn into a pupa. The adult beetle develops inside this pupal case, which remains hidden inside a decaying tree stump all through the winter. The fully-formed adult beetle will not emerge until the weather becomes warmer in May or June of the following year. The cycle then starts over again, as the males fly off in search of a mate. The flight season lasts only until August and by the time winter arrives, all the adult beetles have died.
Feeding: Although it is known that the larva eats decaying wood, scientists are not certain whether adult stag beetles eat anything at all. Some think that they use a special tongue to lick the sap from trees, but others believe that they eat nothing at all.
Stag Beetles and Humans
In both Britain and on the Continent, stag beetles used to be much more common and widespread than they are today. They are still declining in numbers, although Britain has many more than other European countries. Southern England has the highest population of all, and they can also be found in parts of southern East Anglia.
Adult stag beetles are sometimes killed on purpose by people thinking that they are dangerous, but the biggest threat to them, as is the case with most threatened species, is destruction of their habitat. Many woodlands have been cleared of fallen trees, depriving the female beetles of the damp, decaying timber they need for laying their eggs.
The stag beetle is one of the species chosen by the Government to be included in its Biodiversity Action Plan. This means that it is being given special help to increase its numbers. A stag beetle survey is underway and when its current distribution is known for certain, conservation strategies can be worked out. In some areas, owners of woodland are already leaving a proportion of dead or dying timber to help the animals and plants rely on this. The stag beetle will also benefit from this policy.
You can help too: Build a bug hostel, bury a bucket of woodchip or simply leave any tree stumps in your garden to rot down naturally in a log pile. Occasionally, stag beetle larvae may even be found in compost heaps. The more decaying wood there is around, the more places there are available for the female stag beetle to lay her eggs. By helping in this way, we can all play a part in making sure that the stag beetle has a good chance of a safe future.
Image: beetle-stag by Gábor Kovács