Mesnilotrix empiformis (Mesnil, 1976) Mesnil, 1976

O'Hara, James E. & Cerretti, Pierfilippo, 2016, Annotated catalogue of the Tachinidae (Insecta, Diptera) of the Afrotropical Region, with the description of seven new genera, ZooKeys 575, pp. 1-344 : 248-250

Taxon classification Animalia Diptera Tachinidae

Mesnilotrix empiformis (Mesnil, 1976) comb. n. Fig. 7

Type material examined.

Holotype ♂ of Dexiotrix empiformis Mesnil: "Madagascar Centre/ Ambohitantely 1600m/ det Ankazobe/ B. Stuckenberg"; “6.i.58”; “TYPE” [red label]; " Dexiotrix / empiformis Mesn/ L.P. Mesnil det., 1975"; " Mesnilotrix / empiformis (Mesnil, 1976)/ Cerretti, O’Hara & Wood det 2014" (MNHN). Paratype ♂: "Ambohitantely/ Tampoketsi 1600m/ Ankazobe/ 27-XII 56 R.E." (MNHN).

Description.

See Mesnil (1976: 48, as Dexiotrix empiformis ).

Remarks.

The dexiine genus Dexiotrix was erected by Villeneuve (1936e: 330) for the single species Dexiotrix longipennis , based on three females from Sichuan (China). The genus remained monotypic until Mesnil (1976: 48) described Dexiotrix empiformis based on three males from Madagascar, stressing that "tout en appartenant à une autre espèce, rentrent parfaitement dans le genre Dexiotrix Vill." Mesnil did not provide details supporting this claim except to note that affinities between the faunas of Asia and Madagascar are well known. Nothing further was done on this group until Zhang and Shima (2005) redefined the dexiine genus Trixa Meigen to include Dexiotrix and the morphologically similar Trixella Mesnil.

Zhang and Shima (2005) formally assigned empiformis to the newly defined Trixa and included it in their key to the world species of Trixa . However, these authors did not examine specimens of empiformis and based their characterization of the species in the key on the original description of Mesnil (1976). This may be the reason why empiformis does not fully conform to their revised generic diagnosis of Trixa . For instance, Mesnilotrix empiformis possesses a narrow and concave face and a short, cylindrical palpus (Fig. 7c). Both these features are strikingly different from those shared by the remaining Trixa species sensu Zhang and Shima (2005), which have a broad and flat face, and a well-developed, "strongly inflated" palpus. Mesnilotrix empiformis is further characterized by: abdomen long, subcylindrical (Fig. 7e), and gently bent ventrally (Fig. 7a); lateral postpronotal seta and presutural supra-alar seta both enormously developed (Fig. 7b); and anterior and posterior lappets of metathoracic spiracle subequal in size. We therefore conclude that morphological evidence does not support the assignment of empiformis to Trixa .

Shape of the face, palpus, metathoracic spiracular lappets and abdomen are probably derived features that Mesnilotrix empiformis shares with the Malagasy endemic genus Chaetodexia Mesnil (Fig. 3), known from four species. Monophyly of Chaetodexia is supported by one probably derived character state in the male; i.e., the presence of a pair of strong median discal setae on abdominal tergites 3-5 which are subparallel, reclined at about 30° to horizontal and crossed (in lateral view) with the erect median marginal setae of the corresponding tergites (see Fig. 3). Moreover, all species of Chaetodexia possess strong apical and basal scutellar setae (in addition to an even stronger pair of subapical setae) and normally developed outer postpronotal and presutural supra-alar setae. Mesnilotrix empiformis differs by having abdominal tergites 3 and 4 without median discal setae (those on tergite 5 are erect), basal and apical scutellar setae strongly reduced in size (i.e., less than 1/2 the length of subapical setae) and, as mentioned above, outer postpronotal and presutural supra-alar setae both enormously developed. For these reasons we do not believe that empiformis should be assigned to the genus Chaetodexia , nor to any other named dexiine genus, and thus have chosen to erect the new genus Mesnilotrix for it.