Sepedonella castanea Knutson & Deeming, 2018

Knutson, Lloyd V., Deeming, John C. & Ebejer, Martin J., 2018, The Snail-killing Flies (Diptera: Sciomyzidae) of West Africa, Zootaxa 4483 (1), pp. 67-100 : 92-93

Sepedonella castanea Knutson & Deeming sp. n. ³♀

(Figs 27)

Body length 7.00mm, wing length 5.00mm. Head somewhat broader than high. Frons parallel-sided, slightly inflated above antennal bases, shiny black except narrowly yellowish around and between antennal bases. Large, velvety black parafrontal spot situated in shallow depression on either side in contact with eye margin, these spots moderately densely clothed with long black erect setulae. Orbital plates weakly differentiated, with sparse brownish pruinosity and a few short black setulae. Vertex dull black except behind ocelli, where it is subshiny and sparsely brownish pruinose; occiput brownish to yellowish ventrally between cervix and oral margin. A pair of strong fronto-orbitals, no ocellar setae or setulae, 1 pair of strong internal verticals and 1 pair of slightly weaker external verticals. Gena dull black behind, silvery white under lower apex of eye, shiny brownish black extending onto face. 4–5 weak to moderately strong setae at posterior corner of gena, continuing as a single row of setalike setulae along margin of face to near base of antenna, this row situated on narrow band of dense yellowish-white pruinosity. Face devoid of setae, in male uniformly yellowish with moderately dense yellowish-white pruinosity over entire surface, in female shiny brownish black, lighter on oral margin and along eye margin. Scape short, about as long as distance between bases of antennae, yellow. Pedicel elongate, nearly twice the length of postpedicel, rodlike, expanded apically, tawny, with last seta on dorsal surface 1 ½ times longer than the other setae. Postpedicel black, but yellowish around base of arista externally and along entire basal margin internally. Entire arista light yellowish including the moderately long and dense setulae, these longest along middle 1/3 of arista. Palpus yellow.

Thorax yellowish brown ventrally, laterally and extending onto disc of scutum from postpronotal lobe posteriorly; katepisternum posterolaterally and meron with dense whitish pruinosity; scutum inflated before welldefined transverse suture, broadly blackish brown anteriorly, blackish colour extending posteriorly including scutellum and metanotum; 1 strong ntpl; 1 strong sa; 1 weak pa; 4 pairs presuturally and 4 pairs postsuturally of very weak dc; 1 pair strong marginal sc; sides of scutum and surface of scutellar disc with a few fine scattered black setae; area between scutellum and base of abdomen with moderately dense, white pruinosity; group of 6-8 fine black setulae below and behind posterior spiracle; 4 or 5 tiny black setulae on anepimeron below and behind vallar ridge; katatergite ridge bare; about 8 or 9 fine black setae along posterior margin of anepisternum. Wing yellowish-brown hyaline with apical quarter brownish; area between crossveins may be somewhat darkened; anal vein becoming evanescent at middle, not reaching wing margin; veins blackish brown; alula narrow, slightly narrower than second basal cell; surface of wing densely and uniformly covered with short microtrichiae. Haltere with elongate fuscous knob, stem somewhat lighter; row of 6 small but strong setae at midlength on dorsal surface and patch of short black setulae on extreme base; entire haltere densely covered with yellowish pubescence. Coxae and trochanters yellow; upper mesal margin of hind coxa with row of fine setulae; femora yellow, hind femur somewhat brownish diffuse on apical 2/3, extreme apices of fore and mid femora slightly darkened; extreme apex of hind femur blackish dorsally and laterally; fore tibia blackish, extreme base yellowish; mid tibia yellowish brown, apical half slightly darker; hind tibia rather uniformly brownish black except for extreme base, which is yellowish; first 3 tarsomeres of fore tarsus blackish brown, last 2 yellowish white; mid and hind tarsi yellowish brown, fifth tarsomere in both cases whiter; mid femur with strong seta on anterior surface just before midlength; double row of short stout setae on ventral surface of hind femur from basal one third to apex.

Abdomen shiny blackish brown, darker along mid dorsal surface; tergites 1–2 blackish middorsally; last 2 segments black, in ♀ cercus black; sternites yellowish, strongly reduced, lateral membrane very broad; tergites and sternites with sparse covering of moderately long, black, fine setae; male genitalia Fig. 27, surstylus unlike other species of the genus, not elongate, apically quadrately dilated in profile.

Material examined: Holotype: ♂, NIGERIA: Ilaro Forest, 29.xii.1974, M. A. Cornes ( USNM). In poor condition: head and mid legs missing, genitalia preserved in micro vial pinned beneath specimen . Paratypes: 1♀, same data except 2.xii.1973 ; ( USNM). In good condition. CAMEROUN: Ebolowa-Nkuemvone, champs semenciers, 2♂, 22.viii.1967, L . Matile (MNHNP).

Diagnosis: As in other species of Sepedonella , the postocellar setae are absent. The male surstylus is not straplike as in other species of the genus, but is apically greatly expanded and quadrate in form. The broad velvety black mark on the anterior portion of the frons differentiates this species from S. nana , which has that area very weakly pruinose. The thorax of S. castanea is chestnut-coloured, whereas it is bluish black in S. nana . The hind femur of S. castanea lacks the annulus present in S. nana .