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Cordulegaster
bidentata |
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Common Name:
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Sombre Goldenring |
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Odonata |
Order:
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Odonata |
Suborder:
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Anisoptera |
Family:
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Cordulegastridae |
Genus:
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Cordulegaster |
Species:
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C. bidentata |
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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.
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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.
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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.
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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.
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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
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The
Species on Stamps |
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