Neotherevella Lyneborg, 1978

Winterton, Shaun L., Irwin, Michael E. & Mortelmans, Jonas, 2023, Revision of the dune-associated stiletto flies of the genus Neotherevella Lyneborg, 1978 (Therevidae, Therevinae), African Invertebrates 64 (2), pp. 109-138 : 109

Neotherevella Lyneborg

Neotherevella Lyneborg, 1978: 75- Lyneborg (1980: 319 [catalogue]), (1989: 22 [catalogue]); Majer (1997: 527 [key]); Hauser et al. (2017: 1200 [key, synopsis]). Type species: Thereva citrina Becker, 1902: 35.

Neothereva Kröber, 1912b: 138, sensu Lyneborg (1976: 291), nec Kröber (1937: 276). Type species: Thereva citrina Becker, 1902: 35 [incorrect type species designation by Lyneborg (1976)].

Diagnosis.

Extensive erect, white setae on head, body and legs; female frons wide, inner eye margins subparallel to slightly divergent; parafacial setae absent; hind coxal knob relatively minute or absent; elongate macrosetae on tibia and tarsi; series of anteroventral macrosetae on hind femur; wing opaque white with brown markings; male distiphallus narrow, short.

Description.

Small to medium-sized flies extensively covered with erect, elongate pile. Head length and height subequal; frons flat, grey pubescent with pair of large matte black pubescent spots in female (rarely in male); vertex sunken (especially in female); inner margins of female eyes subparallel; gena rounded; male frons width variable, contiguous below anterior ocellus to wider than ocellar tubercle; frons width strongly sexually dimorphic; parafacial without setae; face flat; occiput pubescence dull silver to grey-brown, postocular ridge and occiput in both sexes with macrosetae few in number, single row or irregularly arranged; antenna shorter than to subequal to head length, positioned on lower half of head and directed anteriorly; flagellum shape variable, cylindrical (slightly tapered distally), elliptical or conical, length shorter than or subequal to combined scape and pedicel length, style apical; scape short, less than 3 × pedicel length, cylindrical, noticeably thicker than pedicel and base of flagellum; palpus slender or crassate, mouthparts short. Thorax with central depression of prosternum setose; cervical sclerite lacking macroseta; pleuron with silver pubescence admixed with erect, filiform and lanceolate setae; metanepisternum with postspiracular setae present; metakatepisternum setae absent; scutum covered with lanceolate and filiform adpressed setae, often of variable length and white; scutal chaetotaxy (pairs of macrosetae): notopleural, 3-5; supra alar, 1- 2; post alar, 1; dorsocentral 0-6; scutellar, 2; posterior surfaces of mid- and hind coxae setose, hind coxal knob absent or reduced in size; all legs approximately equal length; fore and mid-femoral anteroventral (av) macrosetae present or absent, hind femur with anteroventral (av) setae as series along segment, posteroventral (pv) macrosetae present or absent; femoral vestiture as filiform setae admixed with adpressed, lanceolate and scale-like setae; tibial macrosetae elongate; claws relatively small; wing cell m3 open or closed; wing white opaque with variable mottled pattern; vein R1 with setae absent (rarely single seta present); wing membrane densely covered with microtrichia. Abdomen shape relatively short or elongate, slightly narrowed along length. Male terminalia with gonocoxites separate medially, posteromedial margins proximal; inner gonocoxal process (igp) present, articulated; posterior outer gonocoxal process (ogp) barely evident; ventral lobe elongate, half the length of gonostylus; phallus with dorsal apodeme of parameral sheath broad, covering aedeagus dorsally or quadrangular, dorsal apodeme separate from gonocoxites, distiphallus narrow, short and directed ventrally, ventral apodeme as single lobe, narrow. Female terminalia with acanthophorite setae present as two sets (A1 and A2), A1 enlarged and elongate; sternite 8 emarginate posteromedially; tergite 8 elongate with anteromedial process; spermathecal sac as single round lobe, two round spermathecae.

Included species.

Neotherevella arenaria (Lyneborg, 1976), N. kozlovi (Zaitzev, 1971a), N. londti sp. nov., N. macularis (Wiedemann, 1828), N. maroccanus sp. nov.

Comments.

Neotherevella was described by Lyneborg (1978) as a clarification of the confused taxonomic concept of the genus Neothereva Kröber, 1912b, itself being a heterogeneous composite of species now placed in Neotherevella and Thereva - the latter of which Neothereva is arguably a synonym (see Lyneborg 1976, 1978). Kröber (1912b) described Neothereva with five Palaearctic species: N. nitidifrons Kröber, 1912b; N. angustifrons , 1912b; N. latifrons (Macquart, 1848); N. citrina (Becker, 1902) and N. frontata Kröber, 1912b. Lyneborg (1976) noted that the essential distinction between Thereva and Neothereva by Kröber (1912b) was that the male eyes are widely separated. Kröber (1929, 1932, 1937) subsequently identified multiple synonyms or novel combinations, as well as including Neothereva as a subgenus of Thereva ( Kröber, 1932). In a catalogue of Palaearctic Therevidae , Kröber (1937) designated N. nitidifrons as the type species of Neothereva . In his revision of the Afrotropical Therevidae , Lyneborg (1976) overlooked this type species designation and incorrectly designated N. citrina (Becker, 1902) as the type species of the genus. Therein, T. frontata and T. nitidifrons were moved to Thereva , T. latifrons implied as a nomen dubium, while Neothereva was more narrowly circumscribed around N. citrina along with the newly-described N. arenaria . Lyneborg (1976) also synonymised N. angustifrons with N. citrina and Thereva macularis Wiedemann, 1828 was moved to Neothereva . Recognising his previously incorrect type species designation for Neothereva , Lyneborg (1978) synonymised Neothereva (sensu Kröber, 1937) with Thereva and transferred N. arenaria , N. citrina and N. macularis to a new genus Neotherevella (again based on the type species as T. citrina ) along with a species described previously in Aristothereva ( A. kozlovi Zaitzev, 1971a).

Neotherevella , Aristothereva and Acantothereva form a closely related group of specialised genera associated with sandy habitats, especially dunes, that is part of a larger clade also comprising the species-rich and widely distributed genera Irwiniella and Acrosathe (see Holston et al. 2007; Holston 2009; Winterton et al. 2016). Neotherevella is differentiated from other therevine genera by the presence of paired dark maculae on a wide female frons (also in the male of N. londti sp. nov.), parafacial setae absent (present in Acrosathe and Acantothereva , variable in Aristothereva ) and a distiphallus that is narrow and curved ventrally (bulbous in Acantothereva ; ornately spinose in Aristothereva ). Other features of this genus variably shared with Acantothereva and Aristothereva include a wide, sunken vertex (especially in females), opaque white wings with dark maculation, reduced hind coxal knob, elongate tibial macrosetae and extensive white pile on the head and body frequently admixed with white scale-like setae. Paired matte-black pubescent maculae on the female frons are present in all species of Neotherevella , but are also found in some species of Acrosathe (for example, notably Acrosathe vialis (Osten Sacken, 1877), suggestive also of the close relationship of these genera.

Neotherevella is widely distributed throughout the Palaearctic Region and disparately in southern Africa. The most eastern species, N. kozlovi , is recorded from China and Uzbekistan. In the Mediterranean Region, N. macularis is widely distributed throughout northern Africa from Israel to Mauritania; the apparently closely related and distinctively coloured N. maroccanus sp. nov. is known only from Morocco.

Key to species of Neotherevella

1	Macrosetae on head, thorax and legs black; matte-black pubescent spots on female frons admixed with erect black setae (southern Africa)	2
-	Macrosetae on head, thorax and legs pale yellow to white, barely distinguishable from extensive white pile; matte-black pubescent spots on female frons without setae (northern Africa to Mongolia)	3
2	Wing cell m3 open; palpi crassate; all femora with ventral macrosetae; male eyes separated by distance greater than width of ocellar tubercle; male frons with two matte- black spots admixed with elongate, erect setae (South Africa)	Neotherevella londti sp. nov
-	Wing cell m3 closed; palpi slender; only hind femur with ventral macrosetae; male eyes almost contiguous below anterior ocellus; male frons lacking matte-black spots (Namibia)	Neotherevella arenaria (Lyneborg)
3	Wing cell m3 open; male eyes separated by distance greater than width of ocellar tubercle (China, Uzbekistan)	Neotherevella kozlovi (Zaitzev)
-	Wing cell m3 closed; male eyes separated by distance less than width of ocellar tubercle (northern Africa, Middle East)	4
4	Male eyes contiguous below anterior ocellus; male covered with extensive yellow pile on scutum, dorsal portion of occiput and dorsally on abdomen, white pile on pleuron lower half of head and laterally on abdomen; flagellum narrow (Morocco) (female unknown)	Neotherevella maroccanus sp. nov.
-	Male eyes separated at narrowest point by width subequal to width of ocellar tubercle; uniform white pile on head, thorax and abdomen; flagellum conical, tapered (Mauritania to Israel, Sudan)	Neotherevella macularis (Wiedemann)