New species of Hercostomus Loew, 1857 from Afrotropics (Diptera: Dolichopodidae) and key to Afrotropical fauna

Five new species of Hercostomus Loew, 1857 from Kenya, Namibia, Tanzania and South Africa are described and illustrated. They belong to the Hercostomus longiventris lineage, which also appears similar to the Palaearctic H. chetifer subgroup and the Oriental H. takagii and H. absimilis groups on the basis of the modified male fore tarsus. The male cercus of almost all Afrotropical species is remarkable in having ventral processes or projections and are conditionally divided into H. nectarophagus and H. perturbus subgroups on the basis of the presence of one or two ventral projections on the cercus, respectively. Hercostomus brandbergensis sp. nov. and H. fedotovae sp. nov. are associated with the H. nectarophagus subgroup; H. koshelevae sp. nov., H. vikhrevi sp. nov., and H. sanipass sp. nov. are associated with the H. perturbus subgroup. The new species differ by fine structures of the male fore tarsus, cercus and postgonite. An identification key to males of 23 Afrotropical species of Hercostomusis compiled for the first time. New records are given for some known species.