Morellia nigricosta

Morellia nigricosta -group

Description. Colouration metallic violaceous blue; wing with maculae. Female with proclinate fronto-orbital seta undeveloped; parafrons almost entirely setulose; interfrontal seta absent. Humerals 3; posthumerals developed or not; parahumeral undeveloped; presutural strong; intra-alar 1; intrapostalar present. Presutural acrostichals undeveloped; one postsutural pair. Prosternum setulose (Fig. 7). Katepisternals 1+2. Postalar wall bare; anterior and posterior suprasquamal ridges bare. Anepimeron and katepimeron setulose. Metakatepisternum setulose above coxa. Greater ampulla, proepisternum and meron bare. Posterior spiracle setulose on posterior margin. Wing with the basal portion of stem-vein bare dorsally and ventrally; apical portion of stemvein bare dorsally and ventrally; Rs node setulose dorsally and ventrally; R4+5 setulose dorsally, and ventrally bare or setulose; M bent forward towards R4+5. Lower calypter enlarged posteriorly, extending under base of scutellum. Subcostal sclerite bare. Fore tibia bare on posteroventral surface. Male mid femur without a preapical protuberance with setae on dorsal surface; without row of developed setae at mid third of anterior surface. Mid tibia bare on anterodorsal surface. Calcar absent. First abdominal sternite setulose. Male terminalia: cercal plate with the median and marginal spined processes on ventral surface; distiphallus without spinules.

Included species: M. nigricosta (Hough), M. xanthoptera (Pamplona).

Comments. At least two Neotropical species have been recognized as belonging to this group: M. nigricosta (Hough) and M. xanthoptera (Pamplona). This species-group was regarded as a genus-ranked taxon in the Muscini phylogeny (Nihei & de Carvalho, 2007a), placed far from the large Morellia clade and more closely related to Ziminellia and Mitroplatia, with which it composes the base of the clade giving rise to Musca, Neomyia, Curranosia, Pyrellia, Sarcopromusca and Dasyphora. The phylogenetic characters supporting the nigricosta -group as a clade were the following (fig. 50 of Nihei & de Carvalho 2007a): katepimeron setulose; brown macula on humeral vein, apex of Sc and R1, apex of R2+3, and crossvein r-m; male mid femur without series of developed setae on median third of the anterior surface; and cercal plate with marginal spined process on ventral face. Here, a formal description of the nigricosta -group as a new genus is not provided as we consider it a premature proposal, at least until more detailed studies support and corroborate it as a valid generic taxon. Interestingly, the molecular analysis of Schuehli et al. (2007) indicated the non-monophyly of Morellia as its two terminal representatives [M. xanthoptera and M. ochricornis Wiedemann (as obscuripes Bigot)] were not closely related.

Distribution (2 species). Neotropical.

References. Pamplona and Couri (1995), de Carvalho and Couri (2002), Nihei and de Carvalho (2007a). [Note: No mention is made of a nigricosta -group in these references, although taxonomic information and/or keys including M. nigricosta and M. xanthoptera are provided.]