Lucanus cervus

Lucanus cervus

Stag Beetle

35-55mm (excluding mandibles of male)

Late May to August

Britain’s largest beetle, the male stag beetle is immediately recognisable due to the huge antler-like mandibles. Found in areas of southern England in old woodland or where large quantities of rotting deciduous wood can be found – but only frequent in a handful of locations. 

A female and two males found in June 2009 near Epping Forest. 

The larger male had a deformed front leg and missing middle left leg - perhaps from moulting complications when emerging from the pupa. 

Larvae feed in rotten wood, often that of oak trees, horse chestnut, beech, buddleia and others - usually below ground where they can take around four years to mature. The adult beetles only live around two months – in which they will take flight in the evenings in search of a mate. Stag beetles can be attracted to tree sap, and some decaying fruits, although many adults never feed. The feeding mouthparts of the adult are adapted only to take in liquids, with the large mandibles of the male being adapted as tools for display and fighting, and the female’s short sharp mandibles being a defensive adaptation.

The orange mouthparts of this male are visible between the mandibles - lapping up sugar & water solution.

An early 3rd instar larva - the body is very translucent with the head capsule appearing very large. 

Eventually the larvae put on a lot of weight and the body becomes as large as the individual below:

Lucanus cervus larvae turn a darker, yellowish colour when mature and ready to pupate. 

The larvae builds a pupal chamber within the soil and rotten wood which protects the vulnerable pupa as it develops into an adult beetle. 

Adults are attracted to light and can often be observed on the pavement below street lamps. Many adults may be seen in a very small area year after year, and these emergence spots are also used by their predators, such as magpies, hedgehogs and domestic cats. The heads and thorax of predated stag beetles will usually be left uneaten, where they often still appear active even without the abdomen.

Male taking off from hand 

Female ready to take off, both specimens found June 2007

Both sexes have matte, slightly pitted, black head and thorax with more smooth, glossy chestnut elytra and small spines on each leg. Mandibles of the male are a more vivid chestnut often with a strong red appearance in sunlight. Males can vary significantly in size, with some being even smaller than females. The mandibles are much larger in relation to the body size on larger males, with a strong downward curve.

Large mating pair - the mandibles of larger males 

will meet the floor and hold the female steady whilst mating. 

(the light covering of hair is also visible on the ventral side of both beetles)

The large white or cream coloured larvae are occasionally found under rotten logs, the head is orange with large, strong mandibles. Larvae curl up in a ‘C’ shape and may try to bite or defecate if handled.

Stag beetles are harmless and very beneficial, but can pinch powerfully with the jaws if handled carelessly.

Male Lucanus cervus - pigment liner illustration, A4.
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One of the best websites on British Stag Beetle life and behaviour can be found here:
http://maria.fremlin.de/stagbeetles/index.html