Plebejus alizadehorum sp. n. from Western Iran (Lepidoptera: Lycaenidae: Polyommatinae: Polyommatini)

A new species of polyommatine lycaenid butterfly (Lycaenidae, Polyommatini), Plebejus alizadehorum sp.  n., is described on the basis of 44  males and 14  females collected in Shaho Mountain, Zagros, Kermanshah Province, Iran, and distinguished from other look-alike polyommatine lycaenids occurring in the region. A  new species is compared with the following externally similar sympatric taxa: Plebejus argus (Linnaeus, 1758), Lycaeides argyrognomon (Bergsträsser, 1789), L.  christophi (Staudinger, 1875), L.  idas (Linnaeus, 1761) and Kretania alcedo (Christoph, 1877). It differs from the above mentioned species of the genera Plebejus Kluk, 1780 and Lycaeides Hübner, 1819 by the absence or presence of the discal spot in the forewing ventral surface. Kretania alcedo has metallic lunules in the submarginal area of the hindwing ventral surface, which are lacking in the new species. A key to all compared taxa is given for better diagnostics.