Revision of the Genera of the Rhagionidae of the World (Diptera: Brachycera)

Abstract

As a group, flies represent one of the most prolific and important elements of our natural world. The order Diptera comprises approximately 150,000 species in approximately 142 families. My research focuses on the Rhagionidae (formerly known as the Leptidae), a family of flies considered to contain some of the most primitive living members of the dipteran suborder Brachycera and believed to have diversified as early as 170 million years ago. The taxonomic classification of the Rhagionidae has been unstable for decades because there are few morphological characters that can be used to support hypotheses of relationship among its members. Much of the morphology in this group, however, has not been examined systematically.

An independent estimate of phylogeny for the group is carried out and presented here, based on 208 morphological characters for 43 ingroup species and molecular characters consisting of 3200+ bp sequences of 28S rDNA of 34 ingroup species. The goal of this work is to better understand how the genera of the Rhagionidae relate to one another and to their kin within the infraorder Tabanomorpha. Ultimately, this knowledge is fundamental for developing a stable classification system for the group.

The Rhagionidae are recognized as a monophyletic group containing four subfamilies containing a total of 17 extant genera. The subfamily Spaniinae is defined by a special modification of tergite 9 of the female genitalia, which is shared by members of Omphalophora, Ptiolina, Spania, Spaniopsis, and Symphoromyia. Omphalophora Becker is resurrected from synonymy with Ptiolina. Spaniinae is defined by having scale-like thoracic hairs, as in Chrysopilus, Schizella and Stylospania. Arthroceratinae contains a single enigmatic genus, Arthroceras. Most females belonging to these three subfamilies have spermathecal duct accessory glands. These structures are reported here for the first time and are unique in Tabanomorpha. The Rhagioninae is the most primitive subfamily of the Rhagionidae. The saw sclerite in the larval mandible may be synapomorphic for this subfamily. Members of Rhagioninae include Atherimorpha, Desmomyia, Rhagio, and Sierramyia gen nov. Rhagina Malloch is recognized as a junior synonym of Rhagio. The Bolbomyiidae are recognized at the family level for the first time. Alloleptis tersus is incertae sedis within Tabanomorpha.

Two new species are described: Schizella woodleyi (from Luzón, Philippines) and Sierramyia chiapasensis (from Chiapas, Mexico). A key is given to the genera of the Rhagionidae with dichotomies leading to all families of Tabanomorpha. Genera of Austroleptidae, Bolbomyiidae, and Rhagionidae are diagnosed and described, with a list of included species for each genus.