Sepedon (Mesosepedon) knutsoni Vala, Gbedjissi and Dossou, 1994

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 : 89-90

Sepedon (Mesosepedon) knutsoni Vala, Gbedjissi and Dossou, 1994 .

(Figs 22–25, plate 8c, e )

References to figures: Vala et al. 1994 (head, postabdomen, genitalia).

Holotype: ♂, 10.vi.1991, BÉNIN, Agnavo, L.G. Gbedjissi ( MNHNP). This species, first discovered by Deeming in Nigeria in 1979, was described by Vala et al. 1994 on the material they collected in the Republic of Benin (formerly Dahomey) in 1991 and 1993 and some specimens collected by Deeming. Our original (previously unpublished) description presented below is based on paratypes from Nigeria and complements that of Vala et al. (1994).

Body length 5.4–7.0mm, wing length 5.5mm. Head yellow; frons shiny except for very slightly yellowish pruinose frontal plates and velvety, yellow spot in front of orbital plate on either side, these spots touching eye margin and with 7 or 8 short black setulae; frons strongly concave; eye margin slightly indented at level of base of antenna; no fronto-orbital spot present, but frons narrowly but densely white pruinose from frontal spot to this indentation; ocellar triangle yellowish-white pruinose; vertex slightly brownish, rest of occiput yellowish; posterior portion of gena with dense silvery-white velvety area that extends along eye margin almost to base of antenna; anterior part of gena and face yellowish; gena and lower portion of face shiny, upper portion of face lightly whitish pruinose; 1 strong fronto-orbital; internal and external verticals strong, of equal size, no ocellar setae or setulae; postocellars slightly stronger than verticals; group of 4 or 5 moderately strong setae and 2 or 3 setulae on either side of cervix; gena with a few fine black setulae, these extending onto face along inner margin of silvery pruinosity beside eye to antennal base, rest of face bare. Scape yellow, in length slightly less than distance between bases of antennae; pedicel fuscous, 4 times length of first, postpedicel 2/3 times length of second, dark brown, but yellowish around base of arista; segments 1 and 2 and base of segment 3 of arista yellowish, rest of arista white, including the very short setulae. Palpus yellow. Thorax yellowish brown, a little whiter ventrally, pleura with dense white pruinosity on lower half, dorsum with faint brownish pattern consisting of a pair of narrow longitudinal vittae connected by broad brownish area beginning at posterior 2/3 and extending onto scutellum; transverse suture well developed, moderately strong ntpl, sa and pa setae, 1 pair weak prsc dc setae, row of short fine setulae extending from these last setae anteriorly to anterior declivity; sides of scutum with scattered fine black setulae; groups of several setulae including 1 somewhat longer in presutural position; pleura with scattered short black setulae, distinct row on ridge behind posterior spiracle; 3 minute setulae at apex of anterior portion of prosternum; no setae on katatergite callus; disc of scutellum flat, with a few fine black setulae. Haltere densely pruinose yellowish-white including stem, knob slightly infuscate, group of 7 or 8 short black setulae dorsally at base of knob. Wing membrane greyish, somewhat more yellowish anteriorly and slightly darker towards apex, with brownish veins and even distribution of microtrichiae; anal vein becoming evanescent beyond middle but distinctly reaching wing margin; alula narrow, about equal in width to second basal cell; posterior crossvein upright, not meeting fourth vein at right angles. Coxae yellow, each with 1 strong marginal seta and several smaller setae; middle femur yellow; hind femur yellowish brown; strong seta on anterior surface of mid femur at mid length with double row of very short, sparsely distributed spinules from near base to apex; all femora with double row of strong ventral spinules from basal 1/3 to apex; front tibia yellowish basally becoming brownish apically; fore tarsus unicolorous brown; mid and hind tarsi unicolorous brown. Abdominal tergites yellowish, posterior margins somewhat darker, uniformly covered with short black setulae, shiny and with very sparse pruinosity, base of abdomen dorsally lacking setulae except for patch of 10–12 setulae in anterolateral corners; setulae along margin of second tergite twice as long as other setulae; sterna yellowish, reduced, each about 1/5 as wide as long. Female with cercus yellowish white.

WEST AFRICA: NIGERIA: Zaria, Samaru, 1♂, 14.x.1969 ; 1♂, 12.xi.1970; 1♀, 18.vi.1966 (USNM); Zaria, Dumbi Wood, pond, 1♂, 17.xi.1969 (USNM); Zaria, Dumbi Wood, 2♀, 25.x.1979 (NMWC); Nr. Kafanchan, Kagoro Forest , 1♂, 26.ii.1977 ( IARS) ; Niger Prov., nr. Mokwa, Zugurma, 1♂, 26.xii.1971 ( USNM) (all collected by Deeming) .

Published records. BÉNIN: Agnavo and NIGERIA: Zaria ( Vala et al. 1994 paratypes).

Biology. Larvae feed on fresh-water oligochaete worms (Vala et al. 2002; Gbedjissi 2003).

Figures

PLATE 8. Figs 35–38, wings of Sciomyzidae: 35—Pherbellia (Graphomyzina) kivuana Verbeke, 36—Pteromicra zariae sp. n., 37—Sepedon (Mesosepedon) knutsoni Vala, Gbedjissi & Dossou, 38—Sepedonella nana (Verbeke); 39—Sepedon (Mesosepedon) knutsoni, habitus, 40—Sepedon (Sepedomyia) nasuta (Verbeke) head, lateral.