The common blue butterfly or European common blue (Polyommatus icarus) is a butterfly in the family Lycaenidae and subfamily Polyommatinae. The butterfly is found throughout the Palearctic. Butterflies in the Polyommatinae are collectively called blues, from the coloring of the wings. Common blue males usually have wings that are blue above with a black-brown border and a white fringe. The females are usually brown above with a blue dusting and orange spots. Taxonomy and phylogeny This species was first described by Siegmund Adrian von Rottemburg in 1775. Vernacular names that have been given to P. icarus include little blew argus, blew argus, mixed argus, selvedg’d argus, ultramarine blue, caerulean butterfly, and alexis. Subspecies Subspecies include: P. i. icarus (Europe, Caucasus, Transcaucasia) P. i. mariscolore (Kane, 1893) (Ireland) P. i. fuchsi (Sheljuzhko, 1928) (South Siberia, Transbaikalia) P. i. omelkoi Dubatolov & Korshunov, 1995 (Amur, Ussuri) P. i. ammosovi (Kurenzov, 1970) (Central Yakutia, Far East, Kamchatka) P. i. fugitiva (Butler, 1881) (Pakistan) P. i. napaea (Grum-Grshimailo, 1891) (Tian-Shan) P. i. zelleri Verity, 1919 Description Polyommatus icarus has a wingspan of . The dorsal side of the wings is an iridescent lilac blue, bright violet-blue, or almost hyacinth-blue with a thin black border. Females' wings are brown or black-brown with a row of red reddish yellow spots along the edges of the wings (marginal spots) and usually some blue at the base. The extent of blue and brown is extremely variable depending on location. The top of the wings in the female may be mostly blue, especially in Ireland and Scotland, but it always has red spots. The ventral side has a greyish or dust-grey base colour in the males and a more brownish hue in the females. Both sexes have a row of red or orange spots along the edge of the hindwing and extending onto the forewing, though they are generally fainter there, particularly in the males, where they are sometimes missing altogether. There are about a dozen black-centered white spots (ocelli) on the hindwing and nine on the forewing. These usually include one in the middle of the forewing cell, absent in Chapman's and Escher's blues. The fringes on the outer edge of the wings are uniform white, not crossed with black lines as in the chalkhill and Adonis blues (that is, the common blue lacks checkering). The caterpillar is small, pale green with yellow stripes and, as usual with