The New World Genera of Parathalassiinae (Diptera: Empidoidea: Dolichopodidae s.l.), with New Species of Thalassophorus and Eothalassius

Abstract The parathalassine genera Thalassophorus Saigusa, Eothalassius Shamshev and Grootaert, and Chimerothalassius Shamshev and Grootaert are recorded from the New World for the first time. Thalassophorus arnaudi Brooks and Cumming sp. nov. is described from specimens collected at coastal localities in British Columbia, Oregon, and California, and represents the second known species in the genus, the type species being T. spinipennis Saigusa, known only from Rishiri Island in Hokkaido Prefecture, Japan. Detailed illustrations of the male genitalia of T. spinipennis are provided. Eothalassius borkenti Cumming and Brooks sp. nov. is described from specimens collected along the Pacific coast of Costa Rica, bringing the total number of described species of this former Southeast Asian genus to three, with one probable additional described species in the Mediterranean region. The genus Chimerothalassius, which was previously known from a single New Zealand species, is recorded from the island of Dominica, based on a female specimen plus a slide-mounted wing of an undescribed species. A new undescribed parathalassiine genus is also recorded from Chile, based on limited material of two undescribed species. A key to the six genera of Parathalassiinae in the New World, including Parathalassius Mik and Microphorella Becker, is given, as are some preliminary remarks on the limits and phylogenetic relationships of the parathalassiine genera.