Taxonomic revision of the Neotropical genus Rhabdotylus Lutz, 1913 (Diptera: Tabanidae)

Abstract Background Here I revise the Neotropical genus Rhabdotylus Lutz, 1913 (Tabaninae: Diachlorini), including redescription of three species that range from Guatemala to Argentina: Rhabdotylus rubrum (Thunberg, 1827), Rhabdotylus venenatum (Osten Sacken, 1886), and Rhabdotylus viridiventris (Macquart, 1838). New information Rhabdotylus planiventris (Wiedemann, 1828) is established as a junior synonym of R. rubrum, syn. nov. A dichotomous identification key based on external morphological characters is provided.


Materials and methods
I examined the type specimens of all species of Rhabdotylus, which are deposited in the following institutions: The Natural History Museum, London, UK (BMNH); Museum für Naturkunde, Berlin, Germany (MFNB); Museum National d'Histoire Naturelle, Paris, France (MNHN); Fundação Instituto Oswaldo Cruz, Rio de Janeiro, Brazil (FIOC); and Uppsala University, Museum of Evolution, Zoology Section, Uppsala, Sweden (UUZM).

Description
Female (holotype). Head. Frons narrow, light brown, with sparse black hairs and silver pollinosity along the margins of the eyes. Frontal Index: 3.65. Divergence Index: 1. Subcallus yellow, with dense yellow pollinosity. Scape and pedicel yellow to light brown, with black hairs and some yellow hairs mixed and some yellow pollinosity. Flagellum orange with short white hairs, apical flagellomeres missing. Clypeus yellow with dense yellow pollinosity and yellow hairs. Gena and postgena yellow with dense yellow pollinosity and yellow hairs. Palpus yellow with yellow hairs.
Thorax. Scutum light brown with sparse black hairs, scutellum yellow to green with sparse black hairs and white pollinosity. Postpronotal lobe and notopleuron yellow to light brown, with white pollinosity and black hairs. Proepisternum and proepimerum yellow with white pollinosity and yellow hairs. Anepisternum, katepisternum, anepimeron, katepimeron, and katatergite yellow with white pollinosity and yellow hairs. Coxa yellow, with white pollinosity and yellow hairs. Femur yellow with yellow hairs and slightly darker with black hairs distally. Tibiae 1 and 2 yellow with white hairs in proximal half, distal half brown with dark brown to black hairs. Tibia 3 brown with dark brown to black hairs. Tarsus brown with dark brown to black hairs. Pterostigma yellow. Venation brown. Halter yellow, with white apex.
Abdomen. Abdomen predominantly yellow to green with sparse black hairs, and white hairs laterally on tergites 1-5. Tergites 1-3 yellow to green with a lighter band distally and sparse black hairs. Remaining tergites slightly darker and with more black hairs distally. Sternites yellow with a thin lighter band distally, and white to yellow hairs.

Materials
Holotype: Abdomen. Abdomen predominantly light brown. Tergites 1-3 light brown with black hairs, with a faintly lighter band distally and some yellow to white hairs. Remaining tergites light brown with black hairs. Sternites 1-3 yellow to light brown with a lighter band distally and yellow to white hairs. Remaining sternites light brown with black hairs.

Discussion
Rhabdotylus planiventris (Fig. 2) is here established as a junior synonym of R. rubrum, and this species may present some color variation on the abdomen. Rhabdotylus rubrum and R. venenatum display differences in color and have distinct geographic distributions, and the apparent absence of intermediate forms suggests that these are indeed separate species. New collecting efforts are needed to increase the representation of this genus in entomological collections and to provide fresh samples for phylogenetic studies, which are necessary to infer the placement of Rhabdotylus in relation to Stibasoma and other Diachlorini genera. Known geographic range of Rhabdotylus viridiventris (Macquart, 1838).