ABSTRACT A new species of Aulacigaster Macquart, 1835 A. zurqui sp. nov., is described from Costa Rica. The new species, which is classified in the plesiomorphica species group following a cladistics analysis, can be separated from all congeners by having a triangular 1st flagellomere and stout body that is uniformly dark-brown to black. An expanded diagnosis of the plesiomorphica group and a modified key to the Neotropical Aulacigaster are provided to accommodate the new species.

Two new species of Cyamops Melander are described, one from the Afrotropical and one from the Neotropical Region. The newly described species are (type locality in parenthesis): Cyamops mathisi sp. nov. (Province Fianarantsoa, Madagascar) and Cyamops manauensis sp. nov. (state of Amazonas, Brazil). Both species can be separated from congeners based on characters of the male genitalia, particularly the shape of the surstyli. A new country, the Ivory Coast, is added to the distribution records of Cyamops nigeriensis, previously known only from Nigeria and Namibia. Updated keys to the Afrotropical and Neotropical species of the genus are also given.

Redescrição do gênero Diopsosoma Malloch (Diptera, Periscelididae). Diopsosoma Malloch, 1932 e sua única espécie conhecida, D. primum Malloch, 1932 são redescritos. O gênero, embora facilmente reconhecível pela cabeça projetada lateralmente em pedúnculos oculares, é praticamente desconhecido. Por isso, apresenta-se sua redescrição em conjunto com breves redescrições de Periscelididae e da subfamília Periscelidinae. Chave para os gêneros de Periscelididae e fotomontagem do holótipo, talvez o único exemplar preservado da espécie, são fornecidas.

Diopsosoma Malloch, 1932 and its only included species, D. primum Malloch, 1932 are redescribed. While the genus is remarkable and easily recognized by its laterally elongate head that is produced into eyestalks, it is otherwise virtually unknown. To bring attention to this extraordinary fly we redescribe it within the context of brief descriptions of the family Periscelididae and subfamily Periscelidinae. We also provide an annotated key to the described genera of Periscelididae and a photographic montage of the holotype, which is perhaps the only preserved specimen of this genus and species.