Tue, 18/10/2016

Chrysocarabus is a subgenus of Carabini, which contains several of the prettiest European Carabus species. Carabus olympiae is one of its mindblowing members. The thought of observing a Chrysocarabus olympiae makes the heart of any coleopteorologist beat faster: it’s a damn beautiful beetle and it has a very restricted range in a pretty wild environment. Moreover, although it is locally not uncommon, it is a challenge to find the species even in suitable habitat!

When my Italian friend and photographer, Gabriele Motta, brought me into contact with Matteo Negro a researcher, responsible for the  LIFE “Carabus” project in Alta Val Sessera I was pretty excited…. Matteo was willing to help me with photographing the beetle. On the sixteenth of July 2015, we finally had an appointment in Val Sessera.

Under here, some images of the alpine habitat of Carabus olympiae. The first image shows a rocky area covered in shrubs and small trees. The second image shows a landscape with less tree cover and a shrubby area with Bluebell, Alpen Rose and ferns.

Carabus olympiae is a highly restricted range Carabus species confined to the higher mountains around Biella. Carabus olympiae was apparently, like many other alpine species with a low dispersion capacity, unable to re-colonise neighbouring areas after the quaternary glacial period. The species was discovered in the summer of 1854 near Bocchetto Sessera by a little girl, named Olimpia Sella, a cousin of the famous entomologist Eugenio Sella. As Carabus olympiae is a steno-endemic species with very specific habitat demands and as it inhabits two very small areas in the Western Alps, the species is considered as an endangered insect species. It is one of the two Carabus species who occur on a Habitat directive species list. Carabus olympiae actively selects both shrubberies with Alpen rose Rhododendron ferrugineum and Bilberry Vaccinium myrtillus, and beech forests with an understorey. The species avoids pastures as well as any form any form of terrain with insufficient cover of shrubs. Too intensive grazing, intensive forest management and the settlement of Ski Stations are a threat to this species. Matteo and his team, who followed radio-tagged specimens observed that the species has a very low natural dispersion capacity (maximum linear dispersal rate seemed to be 777 metres, which is very low). They also observed that specimens venturing into the more open pastures, immediately turned round and moved back into the shrubs.

Under here some images showing the delicate colours of a Carabus olympiae. The individual on the image is a large female with a length of about 35 mm. On the images on can see that the colours can vary slightly depending on the light and the angle from which one looks the beetle.

On the next image, an individual on the run.

The following image shows the Carabus olympiae under the cover of a large fern.

As most of the Carabus species, Carabus olympiae, mainly feeds on molluscs. The species almost exclusively predates the snail species Arianta arbustorum.

Finally, an image from Carabus olympiae in its rocky alpine habitat.

I'd like to thank Matteo Negro for his very pleasant company and help in the field, as well as Gabrielle Motta, for bringing me into contact with Matteo.

The subgenus Chrysocarabus

Under here some images from the different members of the subgenus Chrysocarabus.

Chrysocarabus auronitens, is the most widespread species. It is an old growth forest species found in most of the West and Central European countries.

Under here images from the regular colour morph of Carabus auronitens, followed by the f.i. putzeysi in Soignes, Belgium, Carabus auronitens ssp. festivus in the Montagne Noire, France and Carabus auronitens natio altkirchensis f.i. ignifer/violaceopurpureus in Les Vosges, France.

Chrysocarabus lineatus is found in the Southwestern corner of France and the Cantabrian Mountains of Spain. It is in the lowlands mainly a stenotopic forest species, but it can also be found in Alpine shrub. The species also shows a lot of subspecies and individual colour variations, which I haven’t encountered yet. Under here an image from a female, which I found just above the treeline in the Picos the Europa.

Chrysocarabus splendens has a more restricted range confined to the Pyrénées in France and Spain, and a handful of forests, in The Aude and Tarn in France. Under here images from Carabus splendens ssp. ammonius, in the Montagne Noire and ssp. lapurdanus at Saint-Jean Pied de Port. Most authors consider them as intraspecific variations and agree that none of them merits a subspecific status. Carabus splendens is mainly a forest species, but it can also be found in shrubs, as well as in extensive meadows and grasslands.

Chrysocarabus hispanus is a species endemic to France found in Central South France and South West France. It is a stenotopic forest species showing generally a strong preference for deciduous forests, however in Forêt de Saou, the species shows a strong preference for Conifer Forest.  Under here an image from the huge Carabus hispanus latissimus, found in the Montagne Noire. This female had a body length of almost 40 mm! The next image shows the subspecies dromensis, which was found in Forêt de Saou.

Chrysocarabus rutilans has also a rather restricted range confined to the East Pyrénées and their adjacent areas in France and Spain. The species is mainly found in mid altitude humid forests, but it can also be found in meadows and scrub. Under here an image from Carabus rutilans ssp. perignitus. The image was made in Andorra.

The next image shows a natural hybrid between Carabus rutilans and Carabus hispanus, which is called 'croesus'. Interbreeding experiments have proved that the female 'croesus' specimens can be fertile. When they mate successfully with 'hispanus' or 'rutilans' males, their offspring can have again features resembling very closely a 'hispanus' or 'rutilans'. This specimen is very likely to be a 'croesus' from several generations old, with a dominance of the 'rutilans' characteristics.

Chrysocarabus solieri is another species occupying a small range. It occurs In the South-east of France and in the adjacent Italian montane areas. At the lower altitudes Carabus solieri is strictly a forest species, which can be found in different types of forest, as long as they are humid enough. In the Alpes Maritimes the species occurs in conifer forests, shrubby areas, and deciduous forests ranging from 600 metres till 2000 metres above sea-level. Under here the blue colour morph of Carabus solieri.