Indascia Keiser

Reemer, Menno & Stahls, Gunilla, 2013, Generic revision and species classification of the Microdontinae (Diptera, Syrphidae), ZooKeys 288, pp. 1-213 : 31-32

Indascia Keiser Figs 103-118

Indascia Keiser, 1958: 221. Type species: Ascia brachystoma Wiedemann, 1824: 33, by original designation.

Description.

Body length: 4-10 mm. Small, slender flies with more or less constricted abdomen. Head wider than thorax. Face convex in profile; narrower than to wider than an eye. Lateral oral margins not produced. Vertex flat. Occiput ventrally narrow, dorsally strongly widened. Antennal fossa about as wide as high. Eye bare. Eye margins in male parallel, not converging at level of frons. Antenna shorter to longer than distance between antennal fossa and anterior oral margin. Basoflagellomere as long as to longer than scape, 1.5 to 5 times as long as wide; parallel-sided or with dorsal margin somewhat concave; bare. Postpronotum pilose. Mesoscutum with transverse suture complete. Scutellum semicircular, apex may be slightly acute; without or with very small calcars. Anepisternum convex or sulcate; entirely pilose or with bare part limited to ventral half. Anepimeron entirely pilose. Katepimeron (moderately) convex; bare. Wing: vein R4+5 with or without posterior appendix; vein M1 perpendicular to vein R4+5 and vein M; postero-apical corner of cell r4+5 rectangular, with small appendix; crossvein r-m located within basal 1/4 of cell dm, sometimes very close to base. Abdomen elongate, at least 3 times as long as wide; constricted, with narrowest point at posterior margin of tergite 2 and widest point at tergite 4. Tergites 3 and 4 not fused. Male genitalia: phallus furcate, with furcation point in distal half; epandrium without ventrolateral ridge; surstylus furcate, with anterior part short, posterior part about twice as long.

Diagnosis.

Abdomen constricted. Postpronotum pilose. Mesoscutum with transverse suture complete. Katepimeron bare. Frons laterally without concave area.

Discussion.

Originally this genus was included in the tribe Sphegini , as part of a subfamily Cheilosiinae ( Keiser 1958). Thompson (1969) correctly recognized that it belongs to the Microdontinae , where it has remained since.

Originally, Indascia was based on two species with short antennae and without a posterior appendix on vein R4+5 ( Keiser 1958). In two of the species included in the phylogenetic analyses of Reemer and Ståhls (in press) the antennae are long and the appendix on vein R4+5 is present ( Indascia gigantica sp. n. and Indascia spathulata sp. n.). Both characters are also found in additional undescribed species known to the first author. Therefore, these characters are considered not to be of diagnostic value for this genus.

Superficially, species of Indascia look similar to those of Paramicrodon de Meijere, 1913 (as noticed by Cheng and Thompson 2008). For discussion on similarities with Paramixogaster Brunetti, 1923 see there.

Diversity and distribution.

Described species: 4. At least four undescribed species are known to the first author. The genus appears to be strictly Oriental, with species known from India, Sri Lanka, Pakistan, Thailand and Vietnam. The origin of the type specimens of the type species ('India orientalis’) is not exactly known.