Rosalia longicorn (Rosalia alpina)
|Size||Body length: 15 - 38 mm (2)|
Classified as Vulnerable (VU A1c) on the IUCN Red List 2006 (1), listed on Annexe II of the Convention of Bern and as a priority species on Appendices II and IV of the EC Habitats Directive (3).
The rosalia longicorn is one of the most striking and elegant of all beetles, with its beautiful steely blue-grey colouration and large, dominating black spots (4). The extremely long antennae on the front of the head are also adorned with groups of black hairs, which contrast dramatically with the blue-sky colour of the bare parts, appearing as alternating bands of black and blue (3) (4). Males can be distinguished from females by their longer antennae, which can greatly exceed the length of the body (3).
Wide-ranging, from northern Africa, across Europe and the Middle East to Russia (1).
Deciduous forests where there is a reasonable amount of sunlight exposure - beech forests are preferred in Central Europe but other tree species are also used, such as ash, elm, and field maple (2) (3) (5). Larvae develop in dead, decaying, relatively dry wood, or on living trees in wounds and abrasions (2) (5). Although adults are capable of flight, they are often content to simply remain on or near the tree trunks in which they developed as larvae (3).
Eggs of the rosalia longicorn are deposited in the crevices of bark and the cracks and fissures formed in drying wood of withering tree trunks (5). Larvae take around three years to develop (3), and towards the end of their development, pupation takes place in a chamber close to the surface of the tree trunk, usually between the end of May and the end of June (6). After metamorphosis, adult beetles emerge between June and August (2), depending on the area and altitude (3). The lifespan of the beetle is only three to six weeks, during which mating and egg depositing must occur. Frequently, competitive males are seen fighting before mating, presumably for access to females. Adult beetles feed on sap exuded from the trees, and also on leaves (5).
The rosalia longicorn is largely threatened by habitat loss and destruction due to changes in methods of forest maintenance and felled wood processing. Trees are being cut down and harvested for timber and firewood before they reach a suitable age to be able to support developing larvae, and dead wood is being rapidly removed to facilitate ‘reforestation’ (5) (6). In the past, felled trunks were often stored along forest roads and remained there for long periods of time, attracting groups of breeding rosalia longicorns. Now, felled trunks are usually cut and immediately moved. Forests rich in the preferred habitat of beech and maple have also been transformed into coniferous forests during recent decades. Fertilisers have helped accelerate forest growth and the development of closed canopies, which block out sunlight and prevent the essential drying of dead wood required for larvae development. Indeed, damp, humid conditions promote rotting and fungal growth in dead wood, conditions in which the metamorphosis of larvae into the adult beetle form cannot occur (5). The rosalia longicorn also suffers from collection from the wild for commercial trade, with its distinctive pattern and bright colour making it attractive to collectors (7).
The rosalia longicorn is protected in nearly all of its range nations (4), but it is its diminishing habitat that is perhaps in greater need of protection. It has therefore been generally recommended that more protected habitat be established, particularly forest areas that support old, damaged or dead beech trees. Additionally, landowners should be advised to leave dead wood on the forest floor where possible, or to move it and then leave it in exposed, sunny areas (5). With appropriate methods of forest management these stunning beetles should be able to flourish once more.
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- Metamorphosis: an abrupt physical change from the larval to the adult form.
- Pupation: the process of becoming a pupa, the stage in an insect’s development when huge changes occur that reorganise the larval form into the adult form.
IUCN Red List (May, 2006)
TrekNature (March, 2006)
Insectes.net (March, 2006)
Calabria Natura (March, 2006)
CIRCA: Communications and Information Resource Centre Administrator (March, 2006)
Insekten Wirbeltiere Parasitoide (March, 2006)
Melisch, R. and Schutz, P. (2000) Butterflies and Beetles in Germany. TRAFFIC Bulletin, 18(3). Available at: