Silver-green bluing ( Polyommatus coridon ), ♂
|( Poda , 1761)|
The silver-green blue ( Polyommatus coridon or more correctly Lysandra coridon ) is a butterfly ( butterfly ) from the family of the blue (Lycaenidae). The specific epithet is derived from Corydon, a Greek shepherd name. The species colonizes dry, sunny, sparsely vegetated habitats and, despite the decline in such habitats, is mostly still common and in large numbers. As with many bluebellings, the caterpillars of the silver-green bluebell live in symbiosis with ants . The silver-green blue was the insect of the year 2015.
The moths reach a wingspan of 30 to 35 millimeters. The upper sides of the wings of the males are colored light silvery to green-blue, on the outside of the wing edge they are dark. The blue can be developed differently depending on the occurrence and subspecies. The outer edge is fringed white with dark spots.
The females come in two color variants. In one variant, the upper sides of the wings are dark brown, with only a little bluish dust at the base, and along the outer edge, stronger on the rear wing, only weakly in front, a series of orange spots, black on the outside. In the other variant, the upper sides of the wings are colored more intensely blue than in the males and have a brown color in front of the outer edge (submarginal region).
The underside of the forewings resembles that of the sky-blue bluing ( Polyommatus bellargus ) , which is otherwise easily distinguishable by the strong blue upper side . In the male the basic color is light gray-brown, in the female it is dark brown. The base of the wing shimmers faintly turquoise blue. The black spots on the undersides of the forewings are usually brightly colored. Approximately in the middle on the underside of the hind wings there is a white spot that is drawn out to a point on the wing's outer edge. He points to a white longitudinal wipe that sits between the orange, more or less triangular spots along the outer edge. These spots have a fine black border towards the front and a black point at the back. The species differs from the Eros blue-blue ( Polyommatus eros ) mainly in the undersides of the wings. In this case, the point where it is drawn out is more or less distinctly dark and the black spots are distributed differently.
The caterpillars reach a body length of about 16 millimeters. They have a green basic color and have rows of yellow spots on both sides of the back, yellow vertical stripes on the sides and fine, light hair. They look very similar to the caterpillars of the sky blue bluish, but have a lighter green as the base color and more indistinct yellow spots.
The animals come from north and east Spain across central and southern Europe (central Italy, Corsica, Balkans) east to Ukraine and the Urals and the steppes north of the Caspian Sea . It reaches central Greece, but is missing in Turkey. To the north, the distribution area extends over southern England , northern Germany and most of the Baltic region . In Germany, the species occurs relatively frequently in the southern mountains and in the Alps , while it is rare in the north. The species, which used to be very common in Austria in the Alpine region or in the Alpine foothills , has long been in regression. The animals live on dry limestone lawns and in other dry, sunny and temperature-favored areas that are only covered with isolated bushes and short grasses, exclusively on calcareous, alkaline soils.
Way of life
The adults suck nectar mainly from the mint of the genus oregano ( Origanum vulgare ). If these plants are missing, common horn clover ( Lotus corniculatus ) is preferred, but the animals are also found on pigeon scabiosis ( Scabiosa columbaria ), meadow ( Centaurea jacea ), scabiosa knapweed ( Centaurea scabiosa ) and at least occasionally also on the others Habitat existing flowers. In contrast to other types of bluely, legumes play only an insignificant role as nectar plants. The moths are often found on gravel, where they suckle in damp places. They usually appear in larger groups. In the evening they gather in order to sleep upside down in slightly elevated locations, such as umbellifers that tower above the vegetation.
Flight and caterpillar times
The moths fly annually in one generation from late June to August, at the latest in early October. In the south, two generations fly from May to June and August to September. The caterpillars are found in Central Europe from April to June.
Food of the caterpillars
The females lay their whitish eggs individually at the base of the stems, the leaf axils and only rarely on the leaves of the host plants. Sometimes they are also placed on nearby grasses and stones. The females fly flat over the vegetation and land a little further away in a bare place in order to cover the rest of the way to the egg-laying area on foot. The vegetation is drummed on, after touching the host plants the abdomen is curved to lay eggs. After a few eggs have been deposited, nectar is sucked in in the meantime.
The eggs hibernate, the caterpillars do not hatch until the following spring. Only in Greece does the caterpillar overwinter under stones near ant nests after the first molt. The caterpillars live myrmekophil together with ants . Symbioses are known with some garden ant ( Lasius ) and Myrmica species, with Plagiolepis vindobonensis , with the common lawn ant ( Tetramorium caespitum ) and with the red wood ant ( Formica rufa ). The caterpillars secrete attractants via glands that attract the ants. When touched by ant sensors, they also release a sweet secretion through a gap on the back of the seventh abdomen segment, which the ants eat. On the eighth abdominal segment there are two protrusions that can be pushed forward and that have a wreath of hooks at the end. These two organs are particularly moved when ants are nearby and are supposed to attract them as well. In addition to protecting against predators, the ants sometimes build “shelters” out of loose soil for the caterpillars, which can also have connections to nearby ant nests.
During the day, the caterpillars, which are active at dusk and at night, sit in groups in the rubble or moss under the food plants. These plants can then be recognized by the many ants on the low-lying shoots. Pupation takes place under stones, the pupa is smooth and olive green.
Hazard and protection
In Germany, the silver-green bluish can still be found frequently in many places, although its habitat is increasingly being destroyed. Since the species, in contrast to the clearly more sensitive sky blue blues ( Polyommatus bellargus ), is more tolerant of interventions and occurs, for example, on embankments, roadsides and railway embankments, its existence is not endangered; the species is not listed in Germany's Red List . However, it is endangered in several northern federal states, in Lower Saxony it is highly endangered (category: 2), in Saxony it is even threatened with extinction. In Austria the species is in regression.
Lysandra is, depending on the author, understood as an independent genus or as a subgenus of a broad genus Polyommatus . According to phylogenomic studies (based on the comparison of homologous DNA sequences) the group is monophyletic and sister group of Polyommatus s. st. (including the genera / subgenera Meleagris , Neolysandra , Agrodiaetus , Plebicula ). A current revision on a genetic basis proposes to treat the group as a genus.
The delimitation of the species and the taxonomy within Lysandra is a very difficult problem, on which there is no agreement between different researchers., It is known that there are local populations in southern Europe, some of which are one generation, some of which are two generations a year form; both can live next to each other (sympatric) in the same area. The Italian researcher Ruggero Verity named the univoltine form of southwestern Europe coridons . st., the bivoltine hispana . Later bivoltine populations were discovered in Slovakia, which were promptly described in 1997 as a new species, Polyommatus slovacus . Moreover, in several mountain regions of Spain both mono- as well bivoltine local forms after minor morphological differences, especially staining characteristics of males, recognized as species Lysandra albicans , L.semperi and L.caelestissima described, later came L.gennargenti of Sardinia and P.nufrellensis from Corsica were added. These forms not only hybridize with each other where they occur together, such hybrids have also been detected with the sky-blue bluish Lysandra bellargus , the hybrids have even been erroneously described as a separate species ( Polyommatus polonus ). A differentiation of the forms is not always reliably possible using the methods of DNA barcoding and even the number of chromosomes cannot be used without further ado, this is within Lysandra , even within the species Lysandra coridon s. st. variable, whereby the different number makes the crossing of the species difficult, but not completely prevented. The increased number of chromosomes in L. coridon and related species is not due to polyploidy . In fact, substantial evidence of gene exchange between clans through introgression was found.
The preliminary results of the genetic studies can be summarized as follows: Lysandra coridon and the Spanish Lysandra hispana s.lat. are genetically and morphologically different and, according to the prevailing opinion, different species. L.hispana includes the forms, possibly subspecies or even species albicans and caelestissima . L. coridon forms two genetically separate lines, one western and one eastern, with a contact zone running through the middle of Germany. These are morphologically indistinguishable. The eastern one also includes the bivoltine populations of Southeastern Europe, which do not form a separate taxon. L.gennargenti and L.nufrellensis are forms or subspecies within the Western group.
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