Margdalops venustus, Jindr & Rohác & ek & Barraclough, 2003

Jindr, Rohác, ich, ek & Barraclough, David, 2003, Margdalops, a new African genus of Anthomyzidae (Diptera), comprising six new species, African Invertebrates 44 (2), pp. 1-35 : 18-24

Margdalops venustus sp. n.

( Figs 36–48 , 69 )

Type material: Holotype male, labelled: ‘SO. AFRICA: Natal , Bisley Valley, Pietermaritzburg, 12.XII.1978, R. Earlé, ex bird’s nest cape robin, R. M. Miller’, ‘adult emerged 19.I.1979, E-IIA, ex. bird nest’ (intact, NMSA) . Paratypes: SOUTH AFRICA: KwaZulu-Natal: 1 male, same data as holotype, but emerged 23.i.1979, E-IIA , 1 male, emerged 14.i.1979, E-IIB, 1 male, emerged 16.i.1979, E-IIB, 1 male [no mergence data]; 1 female, same locality, E. 5.xii.1978, R. Earlé, ex bird’s nest, 2.II.XII., cape robin [with puparial shell] ; 1 female, same locality, E. 6.xii.1979, R. Earlé, ex bird’s nest cape robin [with puparial shell] ( NMSA, SMOC) ; 1 female, Enseleni , 28 41’S: 32 03’E, 26.vii.1980, R. M. Miller ( NMSA) ; 1 male, Merrivale, Tschwalabenyoni , 2931’S: 20 15’E, 1000 m, 20.x.1992 ; 1 male, Merrivale, nr. Howick, Stuckenberg farm, at light, 9–13.x.1990, both B. R. Stuckenberg leg. ( NMSA) ; 1 female, Richards Bay , 2832c, at light, 21–24.i.1980, R. Miller & P. Stabbins ( NMSA) ; 1 female, St. Lucia Park , 7–8.x.1983 ; 1 female, Matubatuba Distr., Dukuduku Forest , 7.x.1983, both A. Freidberg leg. ( TAUI) ; 2 males, Zululand, Dukuduku , between St Lucia & Matubatuba, 7–8.iv.1960, B. & P. Stuckenberg ( NMSA) . Limpopo: 1 female, Rt. 1, Soutpansberg, Ingwe Ranch , 1100 m, at light, 24.xii.1994, A. Freidberg ( TAUI) . Eastern Cape: 1 male, Katberg , 4000 ft, 1–13.xi.1932 , 1 male 1 female, 14–26.xi.1932, 2 males 1 female, xii.1932, 1 male, 15–30.i.1933, all R. E. Turner leg. ( BMNH) . Western Cape: 1 female, Mossel Bay , 18–30.xi.1921 , 1 male, xii.1921, 1 female, i.1922, 2 females, ii.1922, all R. E. Turner leg. ( BMNH) . Most paratypes with genit. prep .

Etymology: The species is named ‘ venustus ’ (L. = graceful) because of its strikingly coloured frons with a silvery white and velvety brown pattern.

Description: Male.

Total body length 1.53–2.15 mm. Body bicolorous, brown and whitish yellow.

Head:As long as or slightly longer than high, angular in profile ( Fig. 48 ). Frons relatively narrow because of large eyes ( Fig. 42 ). Occiput concave, brown, medially with 2 convergent, silvery microtomentose stripes. Frons ( Fig. 42 ), ornamented by lateral, silvery white microtomentose stripes reaching from foremost margin of orbit to ventral part of occiput and by medial, velvety dark brown microtomentose band covering most of frons except for ocellar triangle. The brown frontal band is interrupted by a narrow medial, pale brown stripe and is usually obliquely dark striated in front of ocellar triangle. Frontal triangle poorly delimited; ocellar triangle distinctly convex, brown; ocelli large. Orbit anteriorly ochreous (besides silvery microtomentose); frontal lunule pale brown. Face narrow, ochreous, with darker medial stripe and narrow brown lateral margins; gena white and silvery microtomentose, anteriorly with brown margin; postgena whitish yellow. Mouthparts yellow, palpus whitish yellow. Chaetotaxy: pvt short but distinct, with apices meeting medially; vti as long as vte, strongly convergent, often with apices crossed; vte exclinate and with a short inclinate seta behind its base; oc long and thin, markedly proclinate ( Fig. 48 ); 2 long ors and 2 small setulae (the anterior much smaller) in front of the anterior one ( Fig. 48 ), the posterior ors subequal in length to vte, vti, and oc, the anterior ors markedly shorter; 1 long curved vi and 1 subvibrissa (about twothirds length of vi); peristomal setulae short and few; postocular setulae very short and more numerous; 1 longer seta on postgena as usual; palpus with 1 distinct dark seta on apex. Eye convex, elongately ovoid; its longest diameter about 1.4 times as long as shortest one. Gena very narrow anteriorly, widened posteriorly; its minimum depth about 0.08 times as long as shortest eye diameter. Antenna knee-like bent; its scape (minute) and pedicel brown, the latter overlapping base of 1st flagellomere which is bicolorous, brown anteriorly and white posteriorly ( Fig. 48 ); arista about 1.7–1.8 times as long as antenna, long ciliate (not pectinate).

Thorax: Slightly narrower than head, brown dorsally and whitish yellow ventrally. Mesonotum ( Fig. 42 ) brown and sparsely microtomentose, except for two ochreous (anteriorly with sparse silver microtomentum), longitudinally elongate spots between dorsocentral lines reaching up to anterior dc setae; humeral and notopleural areas often lighter brown than mesoscutum; scutellum, on the contrary, darker brown. Pleural areas with a narrow brown longitudinal stripe covering dorsal part (from propleuron to base of abdomen); remainder of pleura whitish yellow. Chaetotaxy (see Fig. 42 ): 1 hu, 2 npl (anterior distinctly longer); 1 distinct (as long as hu) prs; 1 weak sa and 1 longer pa; 2 dc, anterior long (longer than anterior npl) and situated relatively far forwards (in half distance between suture and posterior dc), posterior dc strong, as long as apical sc; 4 rows ac microsetae on suture but no ac behind anterior dc; 2 sc, the apical long, the laterobasal small, shorter than sa; 1 ppl, reduced to microsetula; 2 stpl, the anterior only about half length of the posterior; ventral part of sternopleuron with sparse, fine setae. Scutellum triangular with rounded corners, distinctly convex dorsally. Legs yellow to whitish yellow (coxae, trochanters). f 1 lacking ctenidial spine but bearing a row of posteroventral setae (5–6 long) and a row of somewhat shorter posterodorsal setae. t 2 with usual ventroapical seta. f 3 with a long row of 11–13 posteroventral setae, 4–5 of which in distal third of f 3 shortened and thickened. Wing ( Fig. 69 ) narrow, with brown fumose membrane with dark brown band along anterior margin, up to apex of R 4+5. Veins brown. C without thick spinulae among usual setulae. R 2+3 sinuously bend and running very close to C; R 4+5 also slightly sinuous and distinctly convergent to M towards apex of wing. Discal (dm) cell short and very narrow; r-m situated near its middle. CuA 1 relatively long and, like A 1, not reaching wing margin. Anal (cup) cell and alula very narrow, the latter dark brown. Wing measurements: length 1.54–2.15 mm; width 0.45–0.66 mm, Cs 3: Cs 4 = 2.25–3.00, r-m/dm-cu: dm-cu = 3.57–4.42. Haltere brown, knob usually darker.

Abdomen: All sclerites brown, more shining than thorax. Preabdominal terga broad and transverse, reaching lateral sides of abdomen, all sparsely and shortly setose. T2 partly (laterally) fused with T1 and shorter than T3. T3–T5 subequal in size. T6 weakly sclerotised, pale, reduced to small transverse, slightly asymmetrical sclerite. S1 and S2 small, narrower than S3. S3–S5 relatively broad and becoming somewhat wider posteriorly, S5 being the largest. Postabdominal sterna (S6–S8) asymmetrical, partly fused together and dark like preabdominal terga. S6 (situated ventrolaterally) transversely narrow ventrally and fused with S7 laterally, both short. S7 situated on left side of postabdomen; S8 long (longer than epandrium) and situated dorsally.

Genitalia: Epandrium ( Figs 36, 37 ) moderately long, relatively shortly setose, including the longest dorsomedial setae.Anal opening large, rounded triangular. Cercus markedly enlarged, heavily sclerotised, brown, with laterally expanded and anteriorly bent ventral apex ( Figs 36–37 ). Medandrium ( Fig. 36 ) wide, medially short. Gonostylus ( Figs 37, 40 ) proximally wide, in distal third strongly tapered and curved anterointernally and its apex with 2 blunt teeth (cf. Fig. 36 ); outer side of gonostylus with distinct micropubescence, inner side with scattered setae. Hypandrium not very robust, simple ( Fig. 41 ), with reduced internal lobes; transandrium medioventrally simple, only lateral sides of basal membrane weakly sclerotised (in contrast to Amygdalops species), medially with hyaline transverse tubercles ( Fig. 38 ). Pregonite ( Fig. 41 ) largely fused with hypandrium and incurved, only its posterior part somewhat tuberculiform, with two groups of setae (1 anterior seta and 4 setae on posterior tubercle). Postgonite ( Fig. 41 ) slender, slightly sinuous, apically acute and bearing 1 anterior seta in basal third; membrane attached internally to postgonite (= outer part of folding apparatus) dark striated. Aedeagal part of folding apparatus attached to base of phallapodeme ( Fig. 39 , afa) dorsally membranous and its wall with lenticular grains with spine-like apex; connecting sclerite ( Fig. 39 , cs) elongate, heavily sclerotised. Aedeagal complex ( Fig. 39 ) with robust phallapodeme having asymmetrical bifurcate base.Aedeagus with short frame-like phallophore and large distiphallus composed of voluminous saccus and very slender twisted filum. Saccus largely membranous (only basally with a pair of dark sclerites) and armed with scattered tubercles and fine spines. Filum formed by 2 stripelike sclerites, one overpassing the other at apex. Ejacapodeme small, with slender projection ( Fig. 39 ).

Female differs from male as follows:

Total body length 1.94–2.46 mm.

Face darker than in male, particularly with darker brown medial stripe. f 3 posteroventrally with simple finely setulose armature.Wing measurements: length 1.86– 2.31 mm, width 0.57–0.77 mm, Cs 3: Cs 4 = 2.13–2.63, r-m/dm-cu: dm-cu = 3.12–4.12. Abdomen with transverse preabdominal terga. Preabdominal sterna (S1–S5) variable, ranging from narrow (S4 as long as broad) to as broad as in male (S4 wider than long). Postabdomen ( Figs 43, 47 ) relatively short and wide. T6 wide, posteriorly tapered, with short setae in posterior half. S6 wide, transverse, finely setose. T7 narrow, dorsomedially short because of anterior emargination, with dense short and thick setae. S7 longer than wide ( Fig. 47 ), with a transverse dark stripe separating larger, lighter pigmented and setose posterior part from darker anterior third. T8 dark, transverse, semicircular, with fine setae. S8 dark, narrow, posteroventrally bulging, with deep narrow posteromedial incision. T10 small, rounded pentagonal, darker than cerci, microtomentose and with pair of longer setae. S10 slighty wider and paler than T10, with a row of setulae along posterior margin and microtomentose on disc. Internal sclerotisation of genital chamber complex ( Figs 44, 46 ), composed of 2 pairs of crooked, partly coalesced sclerites and of an anterior faint ring-shaped twisted structure ( Fig. 44 ). Ventral receptacle ( Fig. 46 ) subcylindrical, weakly slerotised and proximally ringed, with apical vermicular projection. Accessory gland on ringed duct with terminal ballshaped dilatation. Spermathecae 1+1 ( Fig. 45 ) spherical, one larger than the other, with small tubercles on surface of basal half, and with narrow (compared to broad membranous duct) sclerotised cervix. Cercus ( Fig. 43 ) comparatively short, pale pigmented, shortly setose.

Discussion: This species forms together with M. bifilum sp. n. and M. caligatus sp. n. the M. venustus -group, the monophyly of which is confirmed by 6 synapomorphies, viz., narrowed dm cell, dilated male cercus, modified gonostylus, basal sclerite of postgonite absent, connecting sclerite strongly sclerotised and cervix of spermatheca narrowed. M. venustus sp. n. can be easily recognised from other Margdalops species by its striking ornamentation of the frons with its medial velvety brown band, contrasting bicoloured antenna and distinctive male cercus, gonostylus and female S7 (see key). Other diagnostic features include peculiarites in the male aedeagal complex (e.g. basal fork of phallapodeme, setosity of postgonite, armature of saccus) and of the female postabdomen (e.g. transverse S6, internal sclerites, ventral receptacle).

Biology: Data associated with some specimens indicate that adults were bred from the nests of the widespread southern African Cape Robin ( Cossypha caffra ). However, the nest is likely to be only a secondary breeding habitat of the species, as the larvae were probably developing in the plant material used in the construction of the nests in question. Adults appear not to be seasonal and were collected from October to February, April and July.

Distribution: The species seems to be common in South Africa, and probably occurs also in Swaziland, Mozambique and Zimbabwe.

Figures

Figs 36–41. Margdalops venustus sp. n., male paratype (S. Africa). 36. External genitalia, caudal view. 37. Same, lateral view. 38. Transandrium, caudal view. 39. Aedeagal complex, lateral view. 40. Gonostylus, sublateral view (widest extension). 41. Hypandrium and associated structures, lateral view. Scales: Fig. 40 = 0.05 mm, others = 0.1 mm. For abbreviations see text.

Figs 42–48. Margdalops venustus sp. n., male and female paratypes (S. Africa). 42. Male head and thorax, dorsal view. 43. Female postabdomen, dorsal view. 44. Female internal sclerites, ventral view. 45. Spermathecae. 46. Female genital chamber with internal sclerites, lateral view. 47. Female postabdomen, ventral view. 48. Male head, lateral view. Scales: Figs 42, 48 = 0.2 mm, others = 0.1 mm. For abbreviations see text.

Figs 69–71. Wings of Margdalops species. 69. M. venustus sp. n., male paratype (S. Africa), 70. M. bifilum sp. n., male paratype (Kenya), 71. M. caligatus sp. n., male paratype (Kenya). Scale = 0.5 mm.