Microdon (Chymophila), Macquart

Reemer, Menno & Stahls, Gunilla, 2013, Generic revision and species classification of the Microdontinae (Diptera, Syrphidae), ZooKeys 288, pp. 1-213 : 41-42

Subgenus Chymophila Macquart Figs 176-180

Chymophila Macquart, 1834: 485. Type species: Chymophila splendens Macquart, 1834: 486, by monotypy.

Chimophila Osten Sacken, 1875: 46. Misspelling.

Eumicrodon Curran, 1925a: 50. Type species: Microdon fulgens Wiedemann, 1830: 82, by original designation. See Cheng and Thompson (2008) for synonymy.

Description.

Body length: 10-16 mm. Broadly built flies with oval to round abdomen and long antennae. Head about as wide as to slightly narrower than thorax. Face convex in profile; slightly narrower to slightly wider than an eye. Lateral oral margins produced. Vertex flat. Occiput ventrally narrow, dorsally widened. Eye bare or very short pilose. Eye margins in male converging at level of frons, with mutual distance 1-3 times as large as width of antennal fossa. Antennal fossa about as wide as high. Antenna longer than distance between antennal fossa and anterior oral margin; basoflagellomere shorter than scape; bare. Postpronotum pilose. Scutellum trapezoid; with calcars. Propleuron pilose. Anepisternum with sulcus; pilose anterodorsally and posteriorly, extensively bare ventrally and medially. Anepimeron entirely pilose. Katepimeron convex; smooth; bare. Katatergum uniformly microtrichose. Wing: vein R4+5 with posterior appendix; vein M1 with outward angle, often with outward appendix, anteriorly recurrent; postero-apical corner of cell r4+5 widely rounded, with or without appendix; crossvein r-m located between basal 1/5 and 1/3 of cell dm. Abdomen oval, 1-1.5 times as long as wide. Tergites 3 and 4 fused. Sternite 1 pilose. Male genitalia: phallus projecting far beyond apex of hypandrium, bent dorsad, furcate basally, with both processes equally long and very slender; epandrium with ventrolateral ridge; surstylus with two wide lobes; subepandrial sclerite with elongate anterior projection projecting well beyond surstylus in lateral view.

Diagnosis.

Vein R4+5 with posterior appendix. Abdomen oval. Vein M1 of characteristic shape: with outward angle, usually with small outward appendix, anteriorly recurrent (Fig. 177). In addition to this character, this subgenus also differs from Microdon s.s. in the aedeagal processes being longer and more slender, and in the subepandrial sclerite projecting anteriorly well beyond the surstylus in lateral view (Fig 178-180).

Discussion.

Species of this group are similar in overall habitus to Microdon s.s. Many species have metallic colours, but some are dull black or have a ‘tiger-striped’ abdomen. Previously, this group was considered to be exclusively Neotropical ( Cheng and Thompson 2008). However, several Oriental and one Japanese species are very similar to the Neotropical species in both external characters and morphology of the male genitalia.

Diversity and distribution.

Described species: 34. Neotropical (25 species), Oriental (7 species), Nearctic (1 species) and Eastern Palaearctic (1 species from southern Japan).