Phengaris alcon
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''Phengaris alcon'', the Alcon blue or Alcon large blue, 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 ...
of the family
Lycaenidae Lycaenidae is the second-largest family of butterflies (behind Nymphalidae, brush-footed butterflies), with over 6,000 species worldwide, whose members are also called gossamer-winged butterflies. They constitute about 30% of the known butterf ...
and is found in
Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a subcontinent of Eurasia and it is located entirel ...
and across the Palearctic to
Siberia Siberia ( ; rus, Сибирь, r=Sibir', p=sʲɪˈbʲirʲ, a=Ru-Сибирь.ogg) is an extensive region, geographical region, constituting all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has been a ...
and
Mongolia Mongolia; Mongolian script: , , ; lit. "Mongol Nation" or "State of Mongolia" () is a landlocked country in East Asia, bordered by Russia to the north and China to the south. It covers an area of , with a population of just 3.3 million, ...
.


Description from Seitz

''L. alcon'' Schiff. (= areas Esp., ''euphemus'' Godt.) (83 a). Large, the male above deep blue, but without brilliant gloss. The female black-brown, dusted with dark blue in the basal area. The dark violet-grey underside has numerous ocelli. ''L. alcon'' is easily distinguished from the following species (''coeligena'', ''euphemus'', ''arcas'', ''arion'', ''arionides'' ...) by the male bearing on the blue disc of the forewing no other black spots but the discocellular lunule. Central Europe and North Asia, from the coast of the North Sea (Hamburg, Bremen, Belgium) to the Mediterranean, and from France to the Altai, Dauria and Tibet, ab. ''nigra'' Wheel, has the males strongly darkened, the females being quite black above. In ab. ''cecinae'' Hormuz. the ocelli of the underside are absent or strongly reduced. In ab. ''pallidior'' Schultz the margin is grey instead of black. — ''marginepunctata'' Gillm. has a row of black dots before the margin, almost parallel with it; found by Hafner at Loitsch and other places in Carniola.— In the form ''rebeli'' Hirschke the blue of the upperside is more brilliant and more extended, the dark margin being reduced, in the female only the apical area black; Styria. — ''monticola'' Stgr. (83 a) has a narrow black margin like ''rebeli'', but the blue is very deep and dark, so dull as in true ''alcon''; from the Alps of Switzerland and the Caucasus. — Egg white, finely reticulated, laid on the flowers of the food-plant (''
Gentiana pneumonanthe ''Gentiana pneumonanthe'', the marsh gentian, is a species of the genus ''Gentiana ''Gentiana'' is a genus of flowering plants belonging to the gentian family (Gentianaceae), the tribe Gentianeae, and the monophyletic subtribe Gentianinae. ...
''). The larva generally does not break through the shell on the upperside, so that the holes of empty eggs are not easily noticed. At first grey, later on reddish brown with dark dorsal line and dark head. The butterflies occur on damp meadows where ''Gentiana'' grows; they are plentiful in such places, sometimes even in abundance, from the end of May into July, in the North not before the end of June.


Taxonomy

There are five subspecies: *''P. a. alcon'' (
Central Europe Central Europe is an area of Europe between Western Europe and Eastern Europe, based on a common historical, social and cultural identity. The Thirty Years' War (1618–1648) between Catholicism and Protestantism significantly shaped the a ...
) *''P. a. jeniseiensis'' (Shjeljuzhko, 1928) (southern
Siberia Siberia ( ; rus, Сибирь, r=Sibir', p=sʲɪˈbʲirʲ, a=Ru-Сибирь.ogg) is an extensive region, geographical region, constituting all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has been a ...
) *''P. a. sevastos'' Rebel & Zerny, 1931 (
Carpathians The Carpathian Mountains or Carpathians () are a range of mountains forming an arc across Central Europe. Roughly long, it is the third-longest European mountain range after the Urals at and the Scandinavian Mountains at . The range stretches ...
) *''P. a. xerophila'' Berger, 1946 (Central Europe) * '' P. a. arenaria'' (
Netherlands ) , anthem = ( en, "William of Nassau") , image_map = , map_caption = , subdivision_type = Sovereign state , subdivision_name = Kingdom of the Netherlands , established_title = Before independence , established_date = Spanish Netherl ...
) There has been controversy over whether ''
Phengaris rebeli ''Phengaris rebeli'' (formerly ''Maculinea rebeli''), common name mountain Alcon blue, is a species of butterfly in the family Lycaenidae. It was first found and described in Styria, Austria, on Mount Hochschwab around 1700. Although it was in ...
'', currently regarded as an ecotype within the Alcons, should be listed as a separate species. The two types are morphologically indistinguishable and molecular analysis has revealed little genetic difference, mostly attributable to localized habitat adaptation. Still some maintain that they should be treated as distinct species, especially for conservation purposes, because they parasitise different host ant colonies and parasitise these ants at different rates, and also rely on different host plant species (''Gentiana pneumonanthe'' in the case of ''Phengaris alcon'' and ''Gentiana cruciata'' in the case of ''Phengaris rebeli'').


Ecology

The species can be seen flying in mid- to late summer. It lays its eggs onto the marsh gentian (''
Gentiana pneumonanthe ''Gentiana pneumonanthe'', the marsh gentian, is a species of the genus ''Gentiana ''Gentiana'' is a genus of flowering plants belonging to the gentian family (Gentianaceae), the tribe Gentianeae, and the monophyletic subtribe Gentianinae. ...
''); in the region of 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 ...
they are sometimes also found on the related willow gentian (''
Gentiana asclepiadea ''Gentiana asclepiadea'', the willow gentian, is a species of flowering plant of the genus ''Gentiana'' in the family Gentianaceae, native to central and eastern Europe from primarily mountain (montane) woodland though it does occur in less woode ...
''). The caterpillars eat no other plants.


Parasitic relationship

Like some other species of Lycaenidae, the
larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. ...
l (caterpillar) stage of ''P. alcon'' depends on support by certain
ant Ants are eusocial insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from vespoid wasp ancestors in the Cretaceous period. More than 13,800 of an estimated total of ...
s; it is therefore known as a
myrmecophile Myrmecophily ( , ) is the term applied to positive interspecies associations between ants and a variety of other organisms, such as plants, other arthropods, and fungi. Myrmecophily refers to mutualistic associations with ants, though in its m ...
. Alcon larvae leave the food plant when they have grown sufficiently (4th
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 ...
, or shedding) and wait on the ground below to be discovered by ants. The larvae emit surface chemicals (
allomone An allomone (from Ancient Greek ' "other" and pheromone) is a type of semiochemical produced and released by an individual of one species that affects the behaviour of a member of another species to the benefit of the originator but not the rec ...
s) that closely match those of ant larvae, causing the ants to carry the Alcon larvae into their nests and place them in their brood chambers. Once adopted into a nest, Alcon larvae are fed the regurgitations of nurse ants (just as other ant brood), a process called
trophallaxis Trophallaxis () is the transfer of food or other fluids among members of a community through mouth-to-mouth ( stomodeal) or anus-to-mouth ( proctodeal) feeding. Along with nutrients, trophallaxis can involve the transfer of molecules such as pher ...
. This parasitic method is known as the "cuckoo" strategy and is an alternative to the predatory strategy employed by most other members of the genus such as '' Phengaris arion''. Though less common, the cuckoo strategy has been found to have several advantages over the predatory strategy. For one, it is more trophically efficient than preying directly on other ant grubs, and as a result, significantly more cuckoo-type larvae can be supported per nest than predatory larvae. Another advantage of cuckoo feeding is that individuals, having pursued a higher degree of social integration, have a higher chance of surviving when a nest is overcrowded or facing food shortage because ants preferentially feed the larvae; compared to the type of scramble competition that can devastate predatory larvae, this contest competition results in much lower mortality. Though the cuckoo strategy has its advantages, it also comes with important costs; with greater host ant specialization comes much more limited ecological niches. When the Alcon larva is fully developed it pupates. Once the adult hatches it will leave the ant nest. Over time, some ant colonies that are parasitized in this manner will slightly change their larva chemicals as a defence, leading to an evolutionary "arms race" between the two species. Generally, Lycaenidae species which have a
myrmecophilous Myrmecophily ( , ) is the term applied to positive interspecies associations between ants and a variety of other organisms, such as plants, other arthropods, and fungi. Myrmecophily refers to mutualistic associations with ants, though in its ...
relationship with the ant
genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...
'' Myrmica'' are locked to primary
host A host is a person responsible for guests at an event or for providing hospitality during it. Host may also refer to: Places * Host, Pennsylvania, a village in Berks County People *Jim Host (born 1937), American businessman * Michel Host ...
specificity. The Alcon blue is unusual in this regard in that it uses different host species in different locations throughout Europe, and often uses multiple host species even within the same location and population. Though it may be adopted into the nests of multiple ''Myrmica'' species within a given site, there is typically one "primary" species with which the locally adapted larvae can best socially integrate, leading to drastically higher survival rates. Across Europe, Alcons are known to use '' Myrmica scabrinodis'', '' Myrmica ruginodis'', ''
Myrmica rubra ''Myrmica rubra'', also known as the common red ant or erroneously the European fire ant, is a species of ant of the genus '' Myrmica'', found all over Europe and is now invasive in some parts of North America and Asia. It is mainly red in colou ...
'', ''Myrmica sabuleti,'' ''Myrmica schencki,'' and rarely ''Myrmica lonae,'' and ''Myrmica specioides''.


Predation

''P. alcon'' larvae are sought underground by the '' Ichneumon eumerus''
wasp A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which look somewhat like wasps, but are in a separate suborder. ...
. On detecting a ''P. alcon'' larva the wasp enters the nest and sprays a pheromone that causes the ants to attack each other. In the resulting confusion the wasp locates the butterfly larva and injects it with its eggs. On
pupation 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 ...
, the wasp eggs hatch and consume the chrysalis from the inside.


See also

* '' Orachrysops niobe'' Brenton blue butterfly from South Africa, with a similar lifecycle


References


External links


David Nash pages on ''Maculinea alcon''





Smell-wars between butterflies and ants
{{Taxonbar, from=Q973034 Phengaris Brood parasites Butterflies of Europe Taxobox binomials not recognized by IUCN