One of the best-known examples stag beetles of the Lucanidae Family, the Lucanus cervus is among the insects characterized by heavily modified mandibles. The males have larger mandibles that are used in combat with the other males of the species, resembling stags. Both their scientific and common names are derived from this characteristic.
Available widely throughout Europe, these beetles fall in the Near Threatened category of the IUCN Red List for Endangered Species. It has been predicted that the depletion of forests and natural habitats through recent trends in Europe pose a grave threat to this species, and it may soon be raised to the “Vulnerable” category.
Nomenclature and Taxonomy
Lucanus Cervus is a member of the genus Lucanus inside the Lucanidae Family. It belongs to the Lucanus Scopoli, 1763. There are 4 subspecies of Lucanus Cervus. Through the original description, as noted by Linnaeus in 1758, the subspecies nominated was Luciano cervus cervus. The remaining are:
- Luciano cervus judaicus (Discovered in 1900).
- Luciano cervus laticornis (Discovered in 1864).
- Luciano cervus turcicus (Discovered in 1843).
- Luciano cervus akbesianus (Discovered in 1896).
The stag beetles showcase sexual dimorphism, meaning that the males are larger than the females. They also have larger mandibles which are, in reality, extremely frail. Rather, the female of the species is the one with a powerful bite. The mandibles of the males resemble the horns of a stag.
The size of these beetles vary from place to place. The stag beetles are larger in the regions of Spain, Netherlands, and Germany, compared to those hailing from the UK or Belgium.
Availability, Distribution, and Habitat
The stag beetles are spread across Europe with the exception of Ireland. They are especially prevalent in the southern region of Germany. They are spread throughout the hilly and mountainous areas of Hungary and Romania. The European part of Turkey is also known to contain stag beetles. They are available in the northern and central parts of Italy, and only in the northern parts of Spain and Portugal. The stag beetles have been noted to be extinct in Denmark and Latvia, and confined to just the south-eastern region of England. Outside of Europe, the stag beetles have also been found in Caucasus, Asia Minor, Syria and the western part of Kazakhstan.
Stag beetles are found in a large number of trees, especially those belonging to the oak, willow, lime and beech families. They can also be found in specific species of trees like black poplar (Populus nigra), ash (Fraxinus excelsior), wild cherry (Prunus avium), and the common walnut (Juglans regia). The young larval stage of the stage beetle is generally found growing near the deadwood of the red oak tree.
Adult stag beetles can be found in tree trunks starting from the early part of summer. The mating season starts in late April and can generally end at the onset of the monsoon/autumn season. A few can even be seen as late as August. Female stag beetles live longer than the males, though both adults live only for a few weeks. The average Lucanus Cervus has a minimum lifespan of about 3 years, with a significant part of their lives spent underground in several developmental (instar) stages, when the larvae convert into pupae.
The female stag beetles lay their eggs underground. The depth is usually 30-50 cm, 100 at most. The eggs are placed in proximity to decaying wood. At birth, the larvae are blind and shaped like the letter “C”.The larvae grow for a long time, feeding on decaying wood from tree stumps, compost heaps, old trees, and shrubs. The larvae use their legs for communication with each other in a process called stridulation.
The complete transformation of the larvae to pupa varies upon places and the associated weather, as well as availability of resources. For example, in Germany, it may take 5-6 years, and at most up to 8 years. The larva can reach up to 10 cms of body height towards the end of the development stage. The adults hatch in October, but remain inside the pupae for hibernation and hardening their exoskeletons.
They emerge on the surface the following summer, looking for sap-containing trunks. Strongly attracted by the saps, the males use their mandibles to fight off other males for a good position. The females arrive later. When the mating session takes place, the males cover up the females for protection against predators. It is during this time that the majority of the male stag beetles die. The females somehow manage to survive, dropping themselves to the ground.
The stag beetles have a large number of predators. Some of the predators include mammals like cats and foxes. The main predators of the stag beetles are birds. The bird tends to attack them at the time they are the most vulnerable, when they are looking forward to mating or laying their eggs. Birds that feed on the stag beetle include hooded crows, magpies, carrion crows, woodpeckers, kestrels, etc.
Conservation and Protection Issues
The stag beetle has been positioned as Near-Threatened on the IUCN Red List. The IUCN (International Union for Conservation of Nature) lists the loss of habitat as the primary cause of concern for the Near-Threatened position of the Stag Beetle in its Red List. Housing developments and rise in human population are some of the few causes that are resulting in the dwindling numbers of Stag beetles throughout Europe.
Depletion of tall trees reduces this beetle’s natural habitat. So the recent trends in depletion of European forests pose a serious concern which warranted a Near Threatened status in the Red List.
According to the Habitats Directive set up by the EU in 1992, the Lucanus Cervus was assigned in the second appendix. The member states are required to designate Special Areas of Conservation (SAC) for the protection of the 220 habitats and the 1000 species listed in Annex 1 and 2.