Cordulegaster bidentata

 
 
Common Name:
Sombre Goldenring
Odonata
Order:
Odonata
Suborder:
Anisoptera
Family:
Cordulegastridae
Genus:
Cordulegaster
Species:
C. bidentata 
The Name
Cordulegaster bidentata (Selys, 1843), the Sombre Goldenring, is endemic to Europe occurring in western, south, southeast and central Europe, and one of seven European Goldenring species. The eastern limit of the species are the Carpathians in the west of the Ukraine. 

Sicilian populations have more extended yellow marks and have been described as a distinct subspecies, C. bidentata sicilica Fraser, 1929. Populations from Calabria have been ascribed to this subspecies, but they show smaller yellow spots and an obvious variability, so that they are intermediate between this subspecies and the nominal one. The populations in the southern Balkans are distinct from C. b. sicilica but have larger yellow spots than the nominal subspecies. The overall systematic organisation of the various members of this taxon remains presently unclear (Boudot, 2001; Boudot et al., 2009).

The Family Cordulegastridae are a family of Odonata (dragonflies) from the suborder Anisoptera. They are commonly known as Spiketails. Some vernacular names for the species of this family are biddie and flying adder. The family is distributed world-wide; all eight species in North America belong to the genus Cordulegaster.

The name Cordulegastridae comes from the Greek kordylinus, 'club-shaped' and gaster, belly. The common name spiketails refers to the females' prominent ovipositor.
 
 
 

 

The Characteristics
Length around 8 cm and wingspan 10cm. Externally this species resembles very much the Cordulegaster boltonii, however, is on the middle abdomen ring only one bar and the back of the head triangle is only black. 

This species seems normal found in chill brooks rich in oxygen and their springs, mostly in tiny source rivlets. Typical and often overlooked larva bodies of water are source escapes with tufa depositions which are spreaded by moss upholsterers and form small, easily flowed through water washbasins. In middle mountain positions such bodies of water freeze in winter completely, hence, the larva development can last up to five years. 

This species is much more localised than Cordulegaster boltonii but is moderately scattered in central and western Europe. It shows very variable densities from one locality to another, ranging from only one visible (reproducing) individual to obviously flourishing populations.
 
 
 
 
 
 

 

The Reproduction and Development
Adults are often hidden and are quite difficult to find. Their larval sites are sometimes difficult to access or recognize, particularly in mountainous areas. As a result, this is a poorly known species that is often overlooked by odonatologists and was in the past erroneously considered to be extinct in some countries. 

The larvae are confined to the sources and upper courses of brooks. The species is thus highly specialized and reproduces mainly in headwater streams, with the best habitats in tufa springs and calcareous small brooks. Its reproducing habitat is often difficult to find. In some areas it seems to have been extirpated in acidified brooks as a result of acid rains, but in other areas it is still recorded in streams with a pH <4. 

The flight time lies between end of May till the end of June. The mating and egg-laying happens as well as with Cordulegaster boltonii. The whole development lasts 3 to 5 years.
 
 

 

The Distribution
Cordulegaster bidentata is endemic to Europe occurring in western, south, southeast and central Europe. The eastern limit of the species are the Carpathians in the west of the Ukraine. In the Balkans and eastern Carpathians, C. bidentata is sometimes found in strong populations. Further genetic work is required to determine the taxonomic status of the different populations.
 

 

The Protection Status
IUCN Red List Category & Criteria listed as Near Threatened. European regional assessment as Near Threatened (NT). EU 27 regional assessment as Near Threatened (NT).

The major threats to this species are drought as a result of global warming, particularly in the south of its range, and water extraction for human use and irrigation. Some populations are threatened by water acidification due to acid rains or conifer plantations and forest closure whereas other populations show not to be affected by this. In the south of France, former flourishing populations are known to be extinct as a result of rainfall deficit and recent very hot summers and related spring exhaustion. In north Greece and other Mediterranean countries, some populations were extinct as a result of water capture directly at the source for irrigation. 

There is no recent record referring to the Sicilian subspecies (Cordulegaster bidentata sicilica) in Sicily, which was always very rare - the last record from Sicily was in 1981 (Galletti and Pavesi 1985, Verschuren 1989). Only few records of C. b. sicilica may correspond to identified breeding sites. 

 

References:
http://www.iucnredlist.org/apps/redlist/details/165498/0
The Species on Stamps
 
   
Bulgaria
2005.06.29
   

 
 
 
 
 

 


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