On the distribution of Dolichopus humilis Van Duzee in the Palaearctic Region and a new synonym (Diptera: Dolichopodidae: Dolichopus latipennis species group).

Dolichopus humilis Van Duzee, 1921 was described from the Alaska-Yukon Territory boundary (Van Duzee et al. 1921), and later recorded from Alaska, Northwest Territories and Greenland (J.R. Vockeroth in Pollet et al. 2004). This species was redescribed and illustrated by Pollet and Böcher (2005). It was never associated with the Dolichopus latipennis species group (= Hygroceleuthus Loew, 1857). Recently Negrobov et al. (2009) reviewed the Dolichopus latipennis species group in the Palaearctic Region and described D. lantsovi Negrobov, Grichanov et Barkalov from the Taimyr and Yamal peninsulas of Siberia. At the time of description the differences in leg setation and coloration between D. lantsovi and D. humilis were considered to be important to distinguish a new species. Recently the junior author examined a long series of D. humilis from Thule (northwest side of the island of Greenland) found in the Zoological Museum of the University of Copenhagen, Denmark (ZMUC). IYG also recently examined new material of D. lantsovi from the arctic region of Eurasia deposited in the Zoological Institute of the Russian Academy of Sciences, St. Petersburg (ZIN). Study of this material has revealed variability in leg setation, coloration and thickness (see below) among the Siberian D. lantsovi and northern American D. humilis specimens that overlaps the two species concepts. Therefore, we do not see any justification in recognizing two separate species.