The Stygian ringlet (''Erebia styx'') is a

butterfly Butterflies are insects in the macrolepidopteran clade Rhopalocera from the order Lepidoptera, which also includes moths. Adult butterflies have large, often brightly coloured wings, and conspicuous, fluttering flight. The group comprise ...

belonging to the subfamily Satyrinae, the "browns", within the family

Nymphalidae The Nymphalidae are the largest family of butterflies, with more than 6,000 species distributed throughout most of the world. Belonging to the superfamily Papilionoidea, they are usually medium-sized to large butterflies. Most species have a red ...

. It is found locally in the

Alps The Alps () ; german: Alpen ; it, Alpi ; rm, Alps ; sl, Alpe . are the highest and most extensive mountain range system that lies entirely in Europe, stretching approximately across seven Alpine countries (from west to east): France, Swi ...

on dry

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

slopes. It is very similar to the Styrian ringlet (''E. stirius'') and has sometimes been included in that species.

Description

It has a wingspan of 46–56 mm.Whalley, Paul (1993) ''The Mitchell Beazley Guide to Butterflies'', Mitchell Beazley, London. The upperwings of both sexes are mostly brown with reddish bands near the edge (postdiscal bands). The bands vary in size and may be dusted with brown in the males.Chinery, Michael (1998) ''Butterflies of Britain and Europe'', HarperCollins, London. Within the bands are a variable number of eyespots (ocelli); these are black with white centres. The forewing has a large eyespot near the tip, often with two white centres. The hindwing has three or four spots. The underside of the male's forewing is largely orange with brown dusting in the basal half and a brown border. Unlike in the Styrian ringlet, the brown border does not taper towards the rear of the wing and has a dark "tooth" projecting into the orangeTolman, Tom & Richard Lewington (2008) ''Collins Butterfly Guide'', HarperCollins, London. The tooth is less conspicuous in the females. The underside of the hindwing is mostly brownish, darker in the basal half. The subspecies ''E. s. triglites'' of the

Bergamo Alps The Bergamasque Alps or Bergamo Alps (Italian: ''Alpi Orobie'', sometimes translated into English as Orobic Alps) are a mountain range in the Italian Alps. They are located in northern Lombardy and named after the city Bergamo, south of the mo ...

and

Monte Generoso Monte Generoso (also known as ''Calvagione'') is a mountain of the Lugano Prealps, located on the border between Switzerland and Italy and between Lake Lugano and Lake Como. The western and southern flanks of the mountain lie in the Swiss cant ...

is more strongly marked than the nominate subspecies ''E. s. styx''. It has a larger postdiscal band and larger eyespots on the upper forewing while the underside of the hindwing sometimes lacks eyespots. The subspecies ''E. s. trentae'' of the

Julian Alps The Julian Alps ( sl, Julijske Alpe, it, Alpi Giulie, , ) are a mountain range of the Southern Limestone Alps that stretch from northeastern Italy to Slovenia, where they rise to 2,864 m at Mount Triglav, the highest peak in Slovenia. A large p ...

is even more strongly marked. It has large eyespots with bright white centres.

Distribution and habitat

It occurs in the Alps at altitudes of 600–2,200 metres. It is found in northern

Italy Italy ( it, Italia ), officially the Italian Republic, ) or the Republic of Italy, is a country in Southern Europe. It is located in the middle of the Mediterranean Sea, and its territory largely coincides with the homonymous geographical ...

from near Monte Generoso to the

Dolomites The Dolomites ( it, Dolomiti ; Ladin: ''Dolomites''; german: Dolomiten ; vec, Dołomiti : fur, Dolomitis), also known as the Dolomite Mountains, Dolomite Alps or Dolomitic Alps, are a mountain range located in northeastern Italy. They form pa ...

, in

Ticino Ticino (), sometimes Tessin (), officially the Republic and Canton of Ticino or less formally the Canton of Ticino,, informally ''Canton Ticino'' ; lmo, Canton Tesin ; german: Kanton Tessin ; french: Canton du Tessin ; rm, Chantun dal Tessin . ...

canton in south-east Switzerland, in the Allgäu Alps in south-east

Germany Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwe ...

, in parts of

Austria Austria, , bar, Östareich officially the Republic of Austria, is a country in the southern part of Central Europe, lying in the Eastern Alps. It is a federation of nine states, one of which is the capital, Vienna, the most populous ...

and in the Julian Alps in

Slovenia Slovenia ( ; sl, Slovenija ), officially the Republic of Slovenia (Slovene: , abbr.: ''RS''), is a country in Central Europe. It is bordered by Italy to the west, Austria to the north, Hungary to the northeast, Croatia to the southeast, an ...

. It inhabits steep limestone slopes with scattered trees and bushes. It favours warm, dry, rocky areas.

Life cycle

The barrel-shaped eggs are grey-brown with brown spots and prominent ribs. The caterpillars are grey-brown with lighter and darker stripes and can reach 20–25 mm in length. They feed on

grasses Poaceae () or Gramineae () is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos and the grasses of natural grassland and species cultivated in lawns ...

, particularly '' Sesleria varia''. They take up to two years to mature, hibernating during the first and penultimate

instar An instar (, from the Latin '' īnstar'', "form", "likeness") is a developmental stage of arthropods, such as insects, between each moult (''ecdysis''), until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or ...

s. The butterfly

pupa A pupa ( la, pupa, "doll"; plural: ''pupae'') is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in thei ...

tes among stones and grass in a green and brown chrysalis. The adults fly from early July until early September. A single brood is produced each year.

References

{{Taxonbar, from=Q2140846 Erebia Butterflies of Europe Butterflies described in 1834