Colobaea occidentalis 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 : 70-72

Colobaea occidentalis Knutson & Deeming sp. n. ³♀

( Figs 1–4)

australis Vala, 1989: 52 (nomen nudum)

Male. Body length, 2.0– 2.4mm. Head almost twice as wide as high. Height of gena 1/ 7 x height of eye. Medifacies strongly narrowed above by expanded anteromedial eye margin, shiny yellow, with low, median carina. Gena and narrow strip between face and orbital margin finely tomentose white. Frons densely matt black except for silvery tomentose parafrontalia from anterior fronto-orbital seta to around antennal bases, lunule light yellow, tomentose. Ocellar triangle subshiny black, not prolonged anteriorly; orbital plate silvery grey with fine whitish tomentum, acuminate anteriorly. Occiput sub-shiny black on upper 2/3, with diagonal greyish tomentose areas on either side of foramen and extending to vertical setae which are on silvery-grey extension of orbital plates; occiput yellow below foramen. Two pairs of fronto-orbital setae, anterior pair slightly shorter; ocellars, postocellars and outer verticals well developed, subequal; inner verticals somewhat longer. Two irregular rows of about 12 short black setae along lower margin of gena extending onto parafacial area and almost reaching anteroventral angle of eyes. A few black setulae on silvery tomentose parafrontalia, on ocellar triangle and around occipital foramen. Dorsolateral occipital margins with strong setulae, lower portion of occiput with 2 or 3 stronger setae. Antennal scape yellow, with row of short setae on dorsoapical margin and several long setae anteroventrally; third segment twice as long as width at base, yellowish dorsobasally, black apically, dorsal margin slightly concave and with rather long white pubescence. Arista white with short white setulae; 4–7 elongate strong setulae dorsobasally. Palpus yellow, several setae near apex; labella yellow. Anteroventral facets of eyes enlarged. Thorax subshiny dorsally with strongly variable pattern of brownish black on yellowish-orange ground colour as in Fig. 2 or almost entirely brownish-black, the postpronotal blackish areas usually separated from mid-dorsal black area by greyish tomentum. Propleuron, anepisternum and anepimeron yellow; faint brownish spot at posterior margin of prothoracic spiracle; scutellum brownish black. Anterior part of vallar (subalar) ridge black, posterior part yellow. Katepisternum yellow with brown triangular spot posteromesally, posterodorsal corner tomentose white. Prosternum yellow. Thoracic chaetotaxy: 1 small ppl, 1 ppn, 1ps, 2 ntpl, 1 sa, 1 pa, 2–3 dc (anterior pair shortest), 0 prsc acr, 1bsc, 1 asc (asc much longer than bsc). Anepisternum bare, anepimeron with 3–6 short setae in patch below vallar ridge, no vallar setae. Katepisternum with 1 or 2 strong setae on tomentose white patch above triangular brown spot; 1 or 2 setulae centrally, only 2–4 strong setae ventroapically. Prosternum bare. Fore coxa slightly less than 2/3 length of fore femur, finely tomentose yellowish white, 2–4 strong setae on external margin below mid length, several smaller setae apically. Mid and hind coxae yellow, hind coxa bare posterodorsally. Fore femur moderately thickened, mostly shiny yellow, darkened apically and along dorsal surface, 2 irregular rows of 6 or 7 setae dorsolaterally; middle femur yellow, 1 strong anterior seta beyond middle, 3 fine setae in row at posteroventral apex; hind femur yellow, 1 strong anterodorsal seta near apical third of length, double row of well developed, rather closely spaced setae ventrally. Fore tibia black, mid and hind tibiae yellow, each tibia with 1 dorsal preapical seta. Front tarsus with segments 1–3 black, segments 4 and 5 yellow, middle and hind tarsi yellow. Wing length 2.3mm. Membrane greyish hyaline; longitudinal veins yellow to brown; crossveins very faintly infuscated. Pterostigma minute, Sc ending close to R1 and R1 ending basad of anterior crossvein; anterior crossvein slightly beyond middle of discal cell; anal vein ending short of wing margin. Haltere orange yellow, squama and squamal ciliae yellowish white. Abdominal terga yellowish brown, lateral margins narrowly yellowish; epandrium mostly dark brown; sterna yellowish. Protandrium well developed, anterior margin of sixth sternum darkly pigmented, extending across venter to dextral side of abdomen. Epandrium with 4 strong setae in transverse row at midlength. Anterior surstyli (Fig. 3) together somewhat in the shape of a clam shell; in lateral view, outline as in a parabolic curve, curved ventral margin with single or double row of short, dark peglike processes and a few very minute, setulae, this row not interrupted or interrupted for only a short distance on posterior margin. Posterior surstylus (not shown in Fig. 3) with broad quadrangular base and a short spine-like anteriorly directed process, and a broader, longer blade-like apical process. In lateral view the 2 processes not visible. In posterior view, apex of larger process rounded apically, with 2 minute but very distinct setulae on antero-apical margin. Anterior end of hypandrium broad, slightly rounded. Phallapodeme lightly pigmented, 3 times as long as ejaculatory apodeme, posterior arms strongly divergent. Female. Body length 2.1–2.4mm. All thoracic pleura entirely yellow, upper margin not at all darkened. 2 dc. Abdominal terga brownish, broadly yellow on sides of segments 1–3. Segments 6 and 7 entirely black, cerci whitish. Wing length 2.2–2.4mm. The Ethiopian specimen has antennal pedicel and postpedicel missing but rest of specimen in perfect condition; the occiput is mainly shiny, medium brownish, with the area below on each side of foramen yellowish; the brownish postpronotal areas are distinctly separated from the mid-dorsal dark area and the paired post-sutural brownish areas by yellow; the scutellum is yellowish-brown.

Diagnosis. Colobaea occidentalis is the first species of the genus described from sub-Saharan Africa. It is most similar to C. pectoralis (Zetterstedt) and C. punctata (Lundbeck) , having an unpatterned wing, frons densely black matt, postpedicel mainly black, twice as long as wide basally and arista with long setulae dorsobasally, 2 pairs of dorsocentral setae on scutum, anepisternum mainly yellow and anterior surstylus with peglike processes. Colobaea pectoralis is known from Britain to the St. Petersburg area ( Russia), Colobaea punctata is known from Britain to northern Kazakhstan, Afghanistan and eastern Siberia and from Egypt (latter specimen not seen by us). The male genitalia of these three species differ in several features, most noticeably in the shape of the anterior surstylus. In C. pectoralis the anterior surstylus is broadened anteriorly and projects posteriorly as an oval lobe; in C. punctata the anterior surstylus is rectangular; and in C. occidentalis (Fig. 3) it is semicircular, somewhat in the shape of a clam shell. The entire upper edge of the propleuron, anepisternum and anepimeron is strongly darkened in C. pectoralis , there is a discrete black spot behind the prothoracic spiracle in C. punctata , but in C. occidentalis the upper thoracic pleura are at most only very slightly darkened, and usually the yellow of the pleuron extends well onto the side of the thoracic dorsum.

Material examined: Holotype ♂, NIGERIA: Zaria, Samaru, mercury vapour trap, 9.ii.1968, J.C. Deeming ( USNM) ; Paratypes: 1♂, 1.ii.1968; 1♂, 6.ii.1967 (damaged genitalia in microvial); 2♀, 11.ii.1968; 1♀, 26.ii.1967 (USNM); 2♀, 11.ii.1968 (IARS); 1♀, 13.i.1968; 1♀, 4.ii.1968; same locality, house light, 1♂, 9.i.1972 ; no further data, 1♂1♀, 22.ii.1976 and 31.xii.1970 (IARS); 1♀, 20.xi.1979 (NMWC) (all collected by Deeming); Nr. Ningi, Kwangi, light trap, 1♀, 20.iii.1975, Nr. Ningi , Diri 1♀, 19.iii.1975, both H. Politzar ( NHMUK) ; Kogin Kano Game Reserve, mercury vapour trap, 1♂, 10.ii.1974, H. Politzar ( NMWC) . NIGER : Maradi, 1♀, 25.ii.1976 , A. Rioux ( IARS). ETHIOPIA: Bezirk Shewa, E . Addis Ababa, National Strasse 4, Lake Basekà, 30km W. Metahara , 0 8°54ʹN 39° 54ʹE, 1♂, 14.iii.1995, X1017, Univ. Bielefeld, M. von Tschirnhaus ( ZSM).

Miller (1995) noted that he had seen a specimen of Colobaea from Gambia.

Biology. Unknown.