Revison of Palaearctic species of the genus Chersodromia Walk. (Diptera, Empididae)

Abstract: The present paper is a revision of the Palaearctic species of the genus Chersodromia Walker, 1849 based on the study of the type specimens and considerable documentary material from various European Museums and Institutions. The Chersodromia species are coastal species, penetrating only rarely inland. Altogether 24 species are known recently from the Palaearctic region but this number is far from definite, the finding of many new species may be anticipated especially along South European, North African and Asiatic coasts. 34 species are known at the present time in the world, the genus is mostly Holarctic in distribution, 8 species are Nearctic, 1 species is known from Panama and 1 from the Hawaii. All species are separated into four natural groups of species, viz., hirta-group, cursitans-group, speculifera-group and incana-group. The Palaearctic species represent, from the zoogeographical point of view, 3 provisional specific isolated groups which may be roughly characterized as North European (7 species), South European (14 specie&) and North East Asiatic (3 species). The Nearctic fauna forms 2 zoogeographically isolated groups of species, the first is distributed along the Atlantic coast (3 species), the second one along the Pacific coast (5 species). Two species are described as new to science, C. hackmani sp.n. from Kamtchatka and C. flavipes sp.n. from Spain. A lectotype is designated for C. difficilis Lundbeck, 1910; C. gratiosa Becker, 1908; C. beckeri Melander, 1928; and for C. colliniana Frey, 1936; the holotype of C. amaura (Becker, 1902) is identified. Female of C. nigrosetosa Chvála, 1970 is described for the first time.

Key words: Diptera, Empididae, revision, Palaearctic, catalogue, zoogeography, key to species, new species, Kamtshatka, Russia, Far East, Spain,