Rugged Ground Beetle
Carabus variolosusFabricius, 1787
Order Beetles (Coleoptera)
Family Ground beetles (Carabidae)
Conservation status: in Bulgaria: Critically Endangered CR [B1ab(i,ii,iii,iv,v)+2ab(i,ii,iii,iv)].
General distribution. Poland, the Czech Republic, Slovakia, Romania, Moldova, the Western Ukraine, Serbia and Bulgaria.
Distribution and abundance in Bulgaria. The only reliable records are from the Western Balkan Range, from where the species was reported in the first two decades of the 20th century. It has been found along the Stara Reka Valley above Varshets [1, 2]. It has been published from the Balkan Range without an exact locality, according to material from the end of the 19th century [3]. In the last 50 years it was not found in Bulgaria. The populations in Bulgaria and Serbia have lower densities because of their relict character.
Habitats. A hygrophilous, sylvicolous and stenotopic species. It inhabits banks of fast flowing mountain rivers and streams, bogs and adjacent forest habitats in mountains and foothills [4].
Biology. The adult dives during the day and the night and may stay under the water surface for about 20-30 minutes. There it hunts on water molluscs, worms, scuds (Gammarus), larvae of water insects (caddisflies, water beetles of the genus Agabus) and young amphibians. The rest of the time it hides under stones or branches, also in the water. The mating takes place there in May, at a depth of up to several decimeters. Egg-laying is in June. The larva and the pupa develop in rotting wood close to the water. The development of the larva lasts for about 35 days, without a diapause. The adult appears in August and does not leave the place of its emerging before the following spring (winter diapause).
Similar species. Carabus cavernosus. The sides of the pronotum of the Rugged ground beetle are more strongly concave in their basal halves and its elytra have a more convex relief and tubercles (and not numerous pits as in Carabus cavernosus).
Negative factors. Decrease of the flow of mountain rivers and streams as a result of their use for domestic needs (irrigation, water supply). In the whole range, it is strongly endangered because of the disappearance of the natural habitat. An indicator of pure riverside forest habitats in Central and Eastern Europe.
Conservation measures taken. None.
Conservation measures needed. Discontinuation of the use of the Stara Reka river as a source of energy or domestic needs. Investigations on the abundance and the area of the population.
References. 1. Rambousek, 1912; 2. Buresch, Kantardjieva, 1928; 3. Apfelbeck, 1904; 4. Turin et al., 2003.
Author: Borislav Gueorguiev
