You can help expand this article with text translated from the corresponding article in Russian. (April 2023) Click [show] for important translation instructions. View a machine-translated version of the Russian article. Machine translation, like DeepL or Google Translate, is a useful starting point for translations, but translators must follow the LLM translation guideline, revise errors as necessary and confirm that the translation is accurate, rather than simply copy-pasting machine-translated text into the English Wikipedia. Do not translate text that appears unreliable or low-quality. If possible, verify the text with references provided in the foreign-language article. You must provide copyright attribution in the edit summary accompanying your translation by providing an interlanguage link to the source of your translation. A model attribution edit summary is Content in this edit is translated from the existing Russian Wikipedia article at [[:ru:Голубянка черноватая]]; see its history for attribution. You may also add the template {{Translated|ru|Голубянка черноватая}} to the talk page. For more guidance, see Wikipedia:Translation.

Dusky large blue
Conservation status
Near Threatened (IUCN 2.3)[1]
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Clade:	Pancrustacea
Class:	Insecta
Order:	Lepidoptera
Family:	Lycaenidae
Genus:	Phengaris
Species:	P. nausithous
Binomial name
Phengaris nausithous (Bergsträsser, 1779)[2]
Synonyms
Glaucopsyche nausithous Maculinea nausithous (Bergsträsser, 1779) Lycaena arcas Rott.

The dusky large blue (Phengaris nausithous) is a species of butterfly in the family Lycaenidae. It is found in Armenia,^[3] Austria, Azerbaijan, Belarus, Bulgaria, Czech Republic, France, Georgia, Germany, Hungary, Kazakhstan, Moldova, Montenegro, the Netherlands, Poland, Romania, Russia, Slovenia, Spain, Switzerland, and Ukraine.^[1][4]

The life cycle of this species is strongly related to the herbaceous plant Sanguisorba officinalis (great burnet).^[2]

L. arcas Rott. (= erebus Knoch) (83 e). Male similar to euphemus, but the female quite black-brown above; particularly recognizable by the underside being coffee-brown and bearing only one row of ocelli, ab. minor Frey are small specimens from Switzerland. In ab. inocellata Sohn the ocelli of the underside are reduced, in ab. lycaonius Schultz they are entirely absent. In the male-ab. lucida Geest the forewing above has the blue lighter and more extended and the black discal spots reduced or obsolete. Throughout Central Europe, from Alsatia to the Ural, Caucasus and Armenia, and from Pommerania and the Lower Rhine to Italy. — Egg like that of euphemus laid on Sanguisorba. The young larva pale, later on purple-brown and finally probably yellowish-brown, at first at the flowers, later on at the leaves of Sanguisorba. The butterflies have exactly the same habits as euphemus, with which they frequently fly together, in July and August; they are usually still more plentiful than euphemus in the places where they occur (damp meadows).^[5]

• 
  Phengaris nausithous ♂
• 
  Phengaris nausithous ♂ △

• Scarce large blue Phengaris teleius
• Mountain Alcon blue Phengaris rebeli
• Alcon large blue Phengaris alcon
• Large blue Phengaris arion

Wikimedia Commons has media related to Phengaris nausithous.

• lepiforum.de Notes on taxonomy. Images.
• Butterfly Conservation Armenia