Brown Argus has a wing span of 24-28 mm. It is recognizable on the warm chocolat brown upperside with the distinct orange spots, a dark mid spot on the front wing and conspicious dark ribs. The underside looks like the underside of Common Blue, but the upper black spots upon the edge of the back wing are placed above each other like a colon (:). In Common Blue they are displaced. It looks very much like Aricia artaxerxes (Northern Brown Argus), but is smaller and with more distinct spots and more conspicious black spots upon the underside. The Aricia artaxerxes flies however mid between Brown Argus' two generations.
Variation: The numbers and the size of the underside spots varie considerably.
Brown Argus flies mid May until late July and mid July until late August in 2 generations. Sometimes in a 3. generation in September. The flight is whirring and not especially persistent. It seeks nectare on many various flowers. Its habitat is unfertilized pastures, sea cliffs, fallow fields and other dry spots. It wanders about and is often seen far away from the breeding areas. It overwinters as a medium size caterpillar in the vegetation close to the surface. The caterpillar's fodderplants are i.e. cranesbill (Geranium) and storksbill (Erodium cicutarium).
The Brown Argus is locally seen in large numbers in suitable places, in Denmark at Røsnæs or Helgenæs, but the frequency is varied. The species seem to have grown during the latest years with a definite frequency-year in 1995.
Source: Michael Stoltze: Dagsommerfugle i Danmark., 1997.
photo Gl. Ry, Midtjylland august 2010: grethe bachmann