Dixa ubiquita

Moulton, John K., 2017, The true identity of Dixa modesta Johannsen (Diptera: Dixidae) resolved: synonymy of Dixa similis Johannsen, designation of the Dixa ubiquita species group, and description of three new eastern Nearctic species, Zootaxa 4216 (3), pp. 247-260 : 249

Dixa ubiquita species group

Diagnosis. Adults of the D. ubiquita group and its closest relatives (i.e., Meringodixa Nowell spp., D. rudis Garrett and allied species, and all Nearctic congeners except D. hegemonica Dyar & Shannon , D. modesta Johannsen , D. neohegemonica Peters , D. notata Loew , and D. terna Loew , are readily distinguished from all other Dixidae by the solid or indistinctly brown striped ( D. brevis , D. rhathyme Dyar & Shannon , and D. lobata sensu Peters , particularly females) scutum and presence of katepisternal (= pre-episternum II of authors) setae. Similarly colored brown species with basal flagellomeres more cylindrical than fusiform (e.g., Dixella indiana (Dyar) , D. nigra (Staeger) , and related species) have a bare katepisternum. Historically used characters, i.e., “fusiform vs. cylindrical” basal flagellomeres and “long versus short” apical gonocoxal lobes do not reliably separate adult Dixa and Dixella Dyar & Shannon species worldwide, especially in the Nearctic Region where nonconforming species exist in each genus. Within the aforementioned group having solid or indistinctly striped brown scutal coloration, D. ubiquita group members are distinguished morphologically from all of these species, except D. brevis , by the narrow, falcate/lanceolate gonostylus (in lateral view). They differ from D. brevis in lacking strong spines (as seen laterally) on the apex of the basal gonocoxal lobe and the cercus being sinuous, posterodorsally directly, and similar in length (i.e., 1.25X) to lateral proctiger width (versus straight, posteroventrally directed, and 2X lateral width of proctiger). Extensive collection data suggest non-overlap between D. brevis and members of the D. ubiquita group (JK Moulton, unpublished).