Spheginobaccha de Meijere

Reemer, Menno & Stahls, Gunilla, 2013, Generic revision and species classification of the Microdontinae (Diptera, Syrphidae), ZooKeys 288, pp. 1-213 : 66-67

Spheginobaccha de Meijere Figs 377-387

Spheginobaccha de Meijere, 1908: 327. Type species: macropoda Bigot, 1883: 331, by monotypy.

Dexiosyrphus Hull, 1944a: 131. Type species: Spheginobaccha funeralis Hull, 1944: 131, by original designation. Described as subgenus of Spheginobaccha .

Description.

Body length: 7-19 mm. Slender flies with short antennae and constricted abdomen. Head about as wide as to wider than thorax. Face in profile straight to slightly concave in dorsal 2/3, with a faint convex tubercle in ventral 1/3; narrower than an eye. Lateral oral margins not produced. Vertex flat. Occiput narrow ventrally, widening dorsally, with distinct crease in dorsal 2/3. Eye bare (African species) or short pilose (Oriental species). Eyes in male not (African species) or strongly (Oriental species) converging at level of frons, in one Oriental species ( Spheginobaccha chilcotti Thompson) even nearly contiguous. Antennal fossa about twice as wide as high. Antenna shorter than distance between antennal fossa and anterior oral margin. Basoflagellomere longer than scape, oval, except more or less triangularly enlarged in males of some African species; bare. Postpronotum pilose. Scutellum semicircular; without calcars. Anepisternum without sulcus; entirely sparsely pilose, sparsely pilose only posteriorly, or entirely bare. Anepimeron pilose on dorsal half or bare. Katepimeron flat; bare or pilose; smooth. Wing vein R4+5 without posterior appendix. Vein M1 oblique and more or less parallel to wing margin, in African species only so in anterior 1/2, posterior 1/2 straight. Postero-apical corner of cell widely rounded and without appendix in Oriental species, rectangular and with appendix in African species. Crossvein r-m located between basal 1/6 to 1/3 of cell dm. Abdomen constricted, narrowest halfway or at posterior margin of tergite 2, widest at tergite 4. Tergites 3 and 4 fused. Male genitalia: phallus unfurcate, straight (African species) or bent dorsad (Oriental species), articulating with hypandrium apically (perialla-group) or basally (macropoda- and rotundiceps-group); hypandrium with apical part consisting of separate lobes; epandrium without ventrolateral ridge; surstylus unfurcate, oval or more or less rectangular to triangular.

Diagnosis.

Metapleura not connected, not forming a postmetacoxal bridge. Abdomen constricted. Occiput with deep crease on dorsal 2/3.

Discussion.

Hull (1949) was the first to include Spheginobaccha in the Microdontinae . Thompson (1969) excluded it, after which Ståhls et al. (2003) included it again. The latter placement was based on a sister-group relationship of Spheginobaccha to all other Microdontinae , as recovered in a phylogenetic analysis of combined molecular and morphological characters. Species can be identified using Thompson (1974), supplemented with Dirickx (1995).

Dexiosyrphus was described by Hull (1949) as a subgenus of Spheginobaccha , based on Spheginobaccha rotundiceps (Loew, 1857). Thompson (1974) argued that if Dexiosyrphus was to be recognized, then another subgenus would have to be erected for the perialla-group. He considered this unnecessary, as the three species groups he recognized were sufficient for proper segregation of the species. We see no reason to adopt a different point of view.

Diversity and distribution.

Described species: 16. Oriental (10 species) and Afrotropical (6 species). Oriental records range from Nepal through Burma, Thailand and Vietnam to Java and Borneo. Afrotropical records are from Malawi, South Africa and Madagascar.