Melanothereva Malloch

Winterton, Shaun L. & Irwin, Michael E., 2023, Revision of the South American stiletto fly genera Entesia Oldroyd and Melanothereva Malloch, with the description of a new genus (Therevidae: Agapophytinae), Zootaxa 5269 (1), pp. 1-82 : 58

Melanothereva Malloch

Melanothereva Malloch, 1932: 249 — Oldroyd (1968: 379 [diagnosis]); Metz & Irwin (2000: 985 [key]); Winterton (2006: 18); Gaimari & Webb (2009: 636 [key]); Webb et al. (2013: 14 [catalogue]); Irwin & Winterton (2020, 2021).

Type species: Thereva lugubris Macquart, 1841a: 302 , by original designation.

Diagnosis. Medium-sized, mostly black flies with dark infuscate wings; antenna shorter than, or subequal to head length; scape subequal to flagellum length; parafacial setae absent; aside from postocular setae row, male sometimes with additional macrosetae scattered on upper occiput; palpi slender; lateral lobe of cervical sclerite sometimes with one or more macrosetae on lateral lobe; prosternum medial setae absent; one pair of scutellar macrosetae; wing cell m 3 open; hind femur lacking macrosetae (rarely present subapically); male abdominal sternite 8 with paired secondary sclerites along posterior margin.

Redescription. Head. Height and length subequal; frons flat or silver pubescent, male frons with eyes contiguous below anterior ocellus; parafacial without setae; gena rounded; mouthparts short, palpus slender; male postocular macrosetae elongate and recurved; male occiput with or without additional row of macrosetae on upper occiput, occiput with silver pubescence; antennae positioned on lower half of head and directed anteriorly, usually shorter than head (rarely same length); flagellum tapered cone-shaped, subequal to combined length of scape + pedicel; scape cylindrical, 3–4x length of pedicel, subequal to flagellum length. Thorax. Medial furrow of prosternum without setae; lateral lobe of cervical sclerite sometimes with a single macroseta; pleuron overlain with very sparse silver pubescence; metanepisternum without setae; scutum with filiform setae, often of variable length; scutal chaetotaxy (pairs of macrosetae): np: 4–5; sa, 1; pa, 1; dc, 2–4; sc, 1; wing dark infuscate; cell m 3 open, veins M 3 and M 4 separate to margin; vein R 2+3 shape a gradual sigmoid curve; vein R 1 with setae absent; wing membrane uniformly covered with microtrichia; posterior surfaces of mid- and hind coxae without setae; hind coxal knob present; femoral velutum patches absent; macrosetae absent on femora, hind femur rarely with anteroventral (av) seta subapically; leg length variable, femora and tibiae approximately equal in length across all legs, hind leg distinctly longer than other legs. Abdomen. Elongate, tapered gradually from base; abdominal tergite 2 with a concentrated patch of short setae posteromedially. Terminalia. Male gonocoxites with velutum patches absent, halves separate medially, posterior outer gonocoxal process well developed, subtriangular; inner gonocoxal process (igp) well developed and articulated; ventral lobe shape variable, usually at least half length of gonostylus, rounded apically; phallus with dorsal apodeme of parameral sheath subtriangular, distiphallus short, abruptly narrowed, ventral apodeme forked. Female with spermathecal sac absent, or when present, as a single lobe with the three spermathecae joining common spermathecal sac duct close to bursa; sternite 8 emarginate posteromedially; acanthophorite macrosetae with two sets, A1 enlarged; tergite 8 elongate with broad anteromedial process.

Included species. Melanothereva bicolorata sp. n., M. frayjorge sp. n. and M. lugubris ( Macquart, 1841a) .

Distribution. South America: Chile, western Argentina, Peru.

Comments. Melanothereva was erected for a single, highly melanised species ( M. lugubri s) with numerous strong macrosetae on the forecoxa. As mentioned previously, the similarity between the two genera suggests that they may be synonymous, but at this stage we find them sufficiently different to maintain them as separate. In their phylogeny of the family, Winterton et al. (2016) recovered Melanothereva in a clade with Entesia and Pachyrrhiza , although relationships amongst the three exemplars were weakly supported.

Key to species of Melanothereva

1. Head, abdomen and dorsal half of thorax uniformly black, frons overlain with dense silver pubescence, scutum with distinct silver pubescent medial vitta; lower half of pleuron and legs bright orange ( Fig. 38 ); lateral lobe of cervical sclerite with macrosetae; male with single row of postocular macrosetae, lacking additional macrosetae scattered on occiput; female with spermathecal sac present...................................................... Melanothereva bicolorata sp. n.

- Body entirely black, overlain with sparse silver pubescence on head and scutum; cervical sclerite without macrosetae; male with additional macrosetae scattered on occiput; female with spermathecal sac absent............................... 2.

2. Scutum mostly black with very sparse brown pubescence medially; male scutum pile very short ( Figs 41 , 42 )................................................................................... Melanothereva lugubris (Macquart) .

- Scutum black with distinct greyish brown pubescence, dense as dorsocentral vittae and joined posteriorly ( Figs 39 , 40 )................................................................................ Melanothereva frayjorge sp. n.

Figures

FIGURE 38. Melanothereva bicolorata sp. n.: A. Female, oblique view; B. same, lateral view.

FIGURE 39. Melanothereva frayjorge sp. n.: A. Male, oblique view; B. same, lateral view.

FIGURE 40. Melanothereva frayjorge sp. n.: A. Female, oblique view; B. same, lateral view.

FIGURE 41. Melanothereva lugubris (Macquart):A. Male, oblique view; B. same, lateral view.

FIGURE 42. Melanothereva lugubris (Macquart):A. Female, oblique view; B. same, lateral view.