A remarkable new genus of stiletto flies from Egypt, with a key to Palaearctic genera of Phycinae (Diptera, Therevidae)

Abstract An unusual new genus (Salwaea burgensis gen. n., sp. n.) of phycine stiletto flies is described from Egypt. A key to Palaearctic genera of Phycinae is presented.


Introduction
The stiletto fly subfamily Phycinae comprises 128 species in 18 genera (four extinct) distributed in all major biogeographic regions except Australasia (Hauser 2005;Hauser and Webb 2007). Diagnostic characters used to differentiate members of this subfamily include absence of lanceolate setae on the femora, setulae on wing vein R 1 (although absent in Schlingeria Irwin, 1977), wing costal vein terminating before vein CuA 2 (never circumambient), palpi with an apical pit, female terminalia with only a single set of variously developed A1 spines on the acanthophorite (tergite 10), abdominal tergites 9 and 10 as separate sclerites, three spermathecae and absence of a spermathecal sac (Lyneborg 1972;Hauser 2005).

Materials and methods
Adult morphological terminology follows McAlpine (1981) and Hauser (2005) with genitalic morphology as modified by Winterton et al. (1999a,b) and Winterton (2006). Genitalia were macerated in 10% KOH to remove soft tissue, then rinsed in distilled water and dilute glacial acetic acid, and dissected in 80% ethanol. Genitalia preparations were placed in glycerine in a genitalia vial mounted on the pin beneath the specimen. Specimen images were taken at different focal points using a digital camera and subsequently combined into a serial montage image using Helicon Focus software. All new nomenclatural acts and literature are registered in ZooBank (Pyle and Michel 2008).

Type species. Salwaea burgensis sp. n. (by present designation)
Diagnosis. Body length: 6.5 mm (female). Antenna longer than head; enlarged bulbous scape with erect strong macrosetae (absent medially); pedicel medio-dorsally inserted on scape; flagellum two-segmented, large paddle-like first flagellomere longer than combined scape and pedicel length, style apical; parafacial without setae; proboscis barely protruding from oral cavity; prosternal depression and mid coxa without setae; metanepisternum without postspiracular setae; hind coxal knob present; costal vein ending just beyond R 4 ; R 1 with single row of setulae; M 1 and M 2 terminating before wing margin; costal margin with scattered setae, not arranged in two rows; cell m 3 closed, petiolate to margin; distal tarsomere with pulvilli and claws relatively small, aligned with axis of leg, dorsal seta[e] on distal tarsomere elongate and projecting; sternite 8 rounded, strongly convex, posteriorly emarginate; tergite 10 as paired sclerites, not fused medially; acanthophorite spines greatly reduced in size.
Etymology. This genus is named in honour of Prof. Dr. Salwa K. Mohammad. Gender is feminine.
Relationship to other phycine genera. It is difficult to identify characters likely to support the phylogenetic placement of Salwaea burgensis gen. et sp. n., as it exhibits a series of both autapomorphies, unique to the taxon, and plesiomorphies, which it shares with all genera of Phycinae. Notable characters found only in this new genus are the large paddle-like shape of the flagellum and the termination of the costal vein just beyond where R 4 joins the wing margin. In all other genera the flagellum ranges from cylindrical to turbinate, while the costal vein is either circumambient (most Therevinae and Agapophytinae), terminates at M 2 (Xestomyzinae) or terminates at various points typically between M 1 and CuA 2 (Phycinae). In rare cases in all subfamilies except Xestomyzinae, individual species have the costal vein terminating in the radial field (typically R 5 ) with medial veins terminating before the wing margin. The reduction of the pulvilli is shared with some species of Pherocera, Orthactia and Phycus. In the latter genus the following species have completely reduced pulvilli: P. annulipes , Lyneborg 1978 (Kenya), P. flavus Lyneborg, 1978 (South Africa), P. lacteipennis Lyneborg, 2002 (Morocco), P. marginatus Kröber, 1912 (Egypt, Chad, Congo, Mali, Nigeria, Senegal, Sudan) and P. mirabilis Lyneborg, 1978 (Botswana, South Africa, Zimbabwe). Some Phycus species have very short and barely discernable pulvilli that may consist only of a pulvillus sclerite remnant: P. angustifrons Lyneborg, 2003 (Thailand), P. insignis Loew, 1874 (Egypt, Middle East to Central Asia), P. kroeberi (Brauns, 1924) (South Africa), and P. stylatus Lyneborg, 1978 (Kenya, Botswana, Tanzania). Although there is no resolved species-level phylogeny for the genus Phycus, taxonomic affinities suggest that pulvilli reduction occurred several times independently in this genus as a derived feature. According to Kröber (1927) the pulvilli are absent in Efflatouniella, although specimens examined have pulvilli that are slightly reduced in a few specimens. The enlarged scape is also found in Neotabuda and Salentia, putative sister genera according to Lyneborg (1980) and Hauser (2005). The furca of Salwaea gen. n. has a distinctive quadrangular shape, suggesting a close relationship with Salentia or Phycus or, perhaps, the pleisomorphic condition of the furca in Phycinae (Fig. 5). Actorthia, Acathrito and Efflatouniella display a very different configuration of the furca whereas the furca of two species of Neotabuda examined are unique among phycines. The furca of Salwaea gen. n. is typical for Phycinae, which always has two compartments, in contrast to the undivided furca type of higher Therevidae like Thereva. The presence of an anteroventral seta on the fore and hind femora in Salwaea gen. n. is also found in Salentia and Neotabuda, but not with Phycus. Diagnosis. See genus diagnosis. Description. Body Length= 6.5 mm (female). Head. Head very wide, 2x head length (excluding antennae); eyes widely separated, frons width at narrowest point 3x width of ocellar tubercle; eye relatively small and globose; frons broadly concave, glossy brown with glaucous (pale bluish) grey pubescence, irregular raised callosities around antennal base and along eye lower margin, callosities with dark erect setae of varying length; parafacial with silver pubescence and glabrous band between antennal base and eye margin; occiput broadly rounded convex with glaucous grey pubescence and scattered erect black macrosetae, longer macrosetae along postocular ridge, medium length on occiput admixed with very short setae; gena rounded with grey-silver pubescence, admixed with short, erect white setae, darker anteriorly, angular process projecting anteriorly from gena with short dark setae; mouthparts reduced, proboscis narrow, barely protruding from oral cavity, palpus not observed as oral cavity obscured; antenna 2× length of head; scape shorter than head length, glossy dark yellow, bulbous and non-symmetrical in lateral view, with dark erect macrosetae (longer ventrally), absent medially, sparse pubescence on medial surface; pedicel brown with row of erect dark macrosetae; flagellum length equal to head, basal flagellomere large, paddle-shaped, style terminal. Thorax. Cuticle dark yellow to brown with dense glaucous grey pubescence, scutum with diffuse medial stripe and light brown patches laterally on prescutal area and supra-alar callus; scutal pile as short dark setae; scutellum dark yellow, overlain with uniform grey pubescence; pleuron dense glaucous grey pubescent with short pale setae on postpronotum, postcervical sclerite, anepisternum, and katatergite; coxae grey glaucous pubescent with short pale setae on anterior surfaces, macrosetae few in number, black; legs dark brown with short dark setae; basitarsus equal length to remaining tarsomeres combined; tarsal segments with short macrosetae apically; tarsal claws short, straight, elongate terminal setae extending from apical segment (one setae on fore and mid leg, three setae on hind leg); haltere stem light brown, knob cream; wing membrane smoky infuscate due to dense microtrichia, darker anteriorly around    pterostigma; scutal chaetotaxy (macrosetae pairs): notopleural, 3; supra alar, 1; post alar, 1; dorsocentral, 2; scutellar, 1. Abdomen. Cuticle glossy dark brown, posterior margins and intersegmental membranes of all segment yellow to white, tergites dark yellow along narrow posterolaterally margin; sparse short dark setae on all segments, denser posteriorly and on terminalia. Female genitalia. Acanthophorite spines reduced in size; sternite 8 emarginate along posterior margin, upturned and strongly convex with elongate setae admixed with shorter setae; furca rectangular, broad at base with two openings.

Salwaea burgensis
Etymology. The species epithet is derived from the type locality, Burg (meaning tower in Arabic), or more recently Borg El-Arab, and is located within Alexandria, Egypt.
Comments. The male of Salwaea burgensis gen. et sp. n. is unknown. The body length is relatively short with a body length of 6.5 mm in the only known female specimen. The type locality is today very close to developed urban areas and this species may possibly be locally extinct there. It is remarkable that despite modern collecting efforts in Egypt and adjacent countries, no further specimens of this stiletto fly have been found.