Macrostomus ferrugineus (Fabricius, 1805), espécie-tipo de Macrostomus Wiedemann, 1817 e Porphyrochroa palliata (Coquillett, 1902), espécie-tipo de Porphyrochroa Melander, 1927 são redescritas e ilustradas a partir dos tipos. Os dois gêneros são neotropicais, considerados grupo-irmãos e suas sinapomorfias são apresentadas. São listadas as espécies pertencentes a ambos os gêneros e as espécies neotropicais que permanecem no gênero heterogêneo Rhamphomyia Meigen, 1822. Uma chave é fornecida para separação dos gêneros próximos e 25 espécies são transferidas ao gênero Porphyrochroa: P. abdominalis (Bezzi, 1905) comb. nov., P. argyrina (Bezzi, 1909) comb. nov., P. barueri (Smith, 1962) comb. nov., P. carrerai (Smith, 1962) comb. nov., P. catarinae (Smith, 1962) comb. nov., P. cyanogaster (Wheeler & Melander, 1901) comb. nov., P. digitata (Smith, 1962) comb. nov., P. distinctipennis (Smith, 1962) comb. nov., P. divisa (Smith, 1962) comb. nov., P. dolichocera (Bezzi, 1905) comb. nov., P. fasciventris (Curran, 1931), P. furcifer (Wheeler & Melander, 1901) comb. nov., P. galactodes (Bezzi, 1909) comb. nov., P. juri (Smith, 1962) comb. nov., P. micrargyra (Bezzi, 1909) comb. nov., P. monstrosa (Bezzi, 1909) comb. nov., P. mundurucu (Smith, 1962) comb. nov., P. mura (Smith, 1962) comb. nov., P. orthoneura (Bezzi, 1905) comb. nov., P. palliata (Coquillett, 1902), P. penicillata (Bezzi, 1909) comb. nov., P. perpulchra (Bezzi, 1909) comb. nov., P. pulchriventris (Bezzi, 1905) comb. nov., P. rotundipennis (Bezzi, 1905) comb. nov., P. seticauda (Smith, 1963) comb. nov., P. variseta (Smith, 1962) comb. nov., and P. wiedemanni (Smith, 1962) comb. nov. A lectotype is designated for P. palliata (Coquillett, 1902).
Macrostomus ferrugineus (Fabricius, 1805), the type-species of Macrostomus Wiedemann, 1817 and Porphyrochroa palliata (Coquillett, 1902), the type-species of Porphyrochroa Melander, 1927 are redescribed and figured from the types. Both Neotropical genera are considered sistergroups and their synapomorphies are presented. The species belonging to both genera, and those Neotropical species remaining in the heterogeneous group Rhamphomyia Meigen, 1822 are listed. A key to genera is provided, 25 species are transferred to Porphyrochroa: P. abdominalis (Bezzi, 1905) comb. nov., P. argyrina (Bezzi, 1909) comb. nov., P. barueri (Smith, 1962) comb. nov., P. carrerai (Smith, 1962) comb. nov., P. catarinae (Smith, 1962) comb. nov., P. cyanogaster (Wheeler & Melander, 1901) comb. nov., P. digitata (Smith, 1962) comb. nov., P. distinctipennis (Smith, 1962) comb. nov., P. divisa (Smith, 1962) comb. nov., P. dolichocera (Bezzi, 1905) comb. nov., P. fasciventris (Curran, 1931), P. furcifer (Wheeler & Melander, 1901) comb. nov., P. galactodes (Bezzi, 1909) comb. nov., P. juri (Smith, 1962) comb. nov., P. micrargyra (Bezzi, 1909) comb. nov., P. monstrosa (Bezzi, 1909) comb. nov., P. mundurucu (Smith, 1962) comb. nov., P. mura (Smith, 1962) comb. nov., P. orthoneura (Bezzi, 1905) comb. nov., P. palliata (Coquillett, 1902), P. penicillata (Bezzi, 1909) comb. nov., P. perpulchra (Bezzi, 1909) comb. nov., P. pulchriventris (Bezzi, 1905) comb. nov., P. rotundipennis (Bezzi, 1905) comb. nov., P. seticauda (Smith, 1963) comb. nov., P. variseta (Smith, 1962) comb. nov. and P. wiedemanni (Smith, 1962) comb. nov. A lectotype is designated for P. palliata (Coquillett, 1902).