Margdalops angustus, 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 : 11-14

Margdalops angustus sp. n.

( Figs 13–23 , 67 )

Type material: Holotype male, labelled: ‘E. Cape Prov., Katberg. 4,000 ft., xii.1932, S. AFRICA: R. E. Turner, Brit. Mus. 1933-69.’ ( BMNH, genit. prep.) . Paratypes: SOUTH AFRICA: KwaZulu-Natal: 1 female, Eshowe, Dlinza Forest Nature Res, 2831 Cd , 450 m, indig. forest, 22.xii.1979, R. Miller & P. Stabbins ( NMSA) ; 1 female, Oribi Gorge Reserve, Umzimkulwana Valley , 21–28.xi.1960 , 1 female, B. & P. Stuckenberg ( NMSA) ; 3 females, Pietermaritzburg, Town Bush , 2.xi.1954, B. Stuckenberg ( NMSA, 1 SMOC) . Eastern Cape: I female (damaged), Transkei, W. The Haven, 3228 Bb , indigenous forest, 25–28.vi.1979, R. Miller & P. Stabbins ( NMSA) ; 1 female, Transkei, 3129cd, Hluleka Nature Res. , 21–25.vii.1981, R. F. Fregona ( NMSA) . Western Cape: 1 female, Groot Rivier Pass nr. Plettenberg Bay , indigenous forest, 11.x.1959, B. & P. Stuckenberg ( NMSA) . Most paratypes with genit. prep .

Etymology: The species is named ‘ angustus ’ (L. = narrow) because of its narrow, silvery microtomentose stripes along the frontal triangle, and the narrow male cercus and gonostylus.

Description: Male.

Total body length 2.10 mm. Body brown to dark brown, only extremities yellow.

Head: Slightly to distinctly longer than high. Occiput and frons as in M. venustus , but frontal triangle distinct, narrow and reaching to anterior two-fifths of frons, silvery white stripes narrower and restricted to boundary between orbits and frontal triangle (thus orbits brown and shiny), and medial stripe in front of frontal triangle narrow and without velvety microtomentum. Ocellar triangle slightly convex, bare. Face and gena whitish yellow, the latter silvery white microtomentose and with a pale brown ventral margin; postgena pale brown, subshiny. Mouthparts yellow, including palpus. Chaetotaxy: pvt short, strongly convergent; vte, vti, oc and posterior ors strong, subequal in length; oc less proclinate, but ors as in M. venustus , 2–3 pairs of microsetulae in front of frontal triangle; vi as long as anterior strong ors, but weaker; subvibrissa about twothirds length of vi. Eye with longest diameter about 1.3 times as long as shortest one. Gena posteriorly slightly widened; its minimum depth 0.06 times as long as shortest eye diameter. Antenna with scape, pedicel and anterodorsal half of 1st flagellomere pale brown, remainder of latter whitish yellow. Arista 1.9 times as long as antenna, longer and more densely ciliate than that of M. venustus .

Thorax: Dark brown, sparsely brownish, only mesoscutum anteromedially whitish grey, microtomentose. Chaetotaxy as in M. venustus but anterior dc longer and situated more anteriorly; anterior stpl about two-thirds length of the posterior. Scutellum convex dorsally. Legs yellow. Pedal chaetotaxies as in M. venustus ; f 3 with a posteroventral row of about 12 setae, 5 of which (in apical third of femur) are shortened and thickened. Wing pattern ( Fig. 67 ) differs from that of M. venustus : dark band along anterior margin longer, basally also distinct near R 1. R 2+3 very long, subparallel to C. R 4+5 very slightly and gradually converging to M distally. Discal cell wider than that of M. venustus and r-m situated in its basal two-fifths. CuA 1 straight, nearly reaching wing margin. Wing measurements: length 2.18 mm; width 0.67 mm, Cs 3: Cs 4 = 4.17, r-m/dm-cu: dm-cu = 4.00. Haltere dark brown.

Abdomen: Dark brown. Preabdominal terga broad, transverse, with sparse, short and thick setae. Sterna S2–S5 narrower than in M. venustus , becoming wider posteriorly. S3 1.5 times as long as wide, S4 slightly longer than wide, S5 distinctly wider than long, broader posteriorly, with shallow posteromedial emargination. T6 small, membraneous, barely visible. S6–S7 as in M. venustus , but S6 and S7 more coalesced and S8 shorter.

Genitalia: Epandrium ( Figs 13, 14 ) longest of all congeners, broad, with moderate setosity, dorsomedial pair od setae longest and strong. Anal opening relatively small, rounded triangular, dorsomedially strongly narrowed. Cercus slender and long, well sclerotised, with blunt apex and microtomentum on posterior side ( Figs 13–14 ). Medandrium ( Fig. 13 ) reduced, very low dorsomedially. Gonostylus (14, 18) slender, distinctly curved, gradually tapered towards apex which terminates in 2 small teeth; its outer side with micropubescence restricted to middle two-thirds; inner side with scattered setae. Hypandrium slender, simple ( Fig. 16 ); transandrium almost straight ( Fig. 15 ); basal membrane medially with small transverse tubercles. Pregonite ( Fig. 16 ) with 2 setae in anterior and 2 in posterior group. Postgonite ( Fig. 16 ) slender, small, tapered, but apex not very pointed, with 1 setula in basal third; besides very finely striated membrane there is a dark band-shaped sclerite attached to base of postgonite.Aedeagal part of folding apparatus with short spine-like hyaline tubercles; connecting sclerite ( Fig. 17 ) very slender, weakly sclerotised.Aedeagal complex ( Fig. 17 ) with moderately developed phallapodeme having shortly bifurcate base and somewhat dilated apex. Saccus of distiphallus voluminous, membranous but its basal half weakly sclerotised in addition to 2 basal sclerites; its membrane armed by dense fine setulae (dorsopreapically) and spinulae on tubercles (ventropreapically). Filum robust, formed by 2 largely fused, only distally diverging sclerites which apically end in several sharp processes ( Fig. 17 ). Ejacapodeme (not figured) relatively large, similar to that of M. signatus , but its long projection with simple apex.

Female differs from male as follows:

Total body length 2.34–2.98 mm.

Face, gena and antenna somewhat darker yellow; 1st flagellomere anterodorsally brown. Microsetulae medially in front of frontal triangle more numerous (3–5 pairs). f 3 posteroventrally finely setulose.Wing measurements: length 2.26–2.94 mm;width 0.69– 0.87 mm, Cs 3: Cs 4 = 2.82–3.92, r-m/dm-cu: dm-cu = 3.46–4.18.Abdomen with T2–T5 more transverse. T2 distinctly shorter than T3; T4 the longest. Sterna paler brown than terga, narrow, pleural membrane large. S2 as long as wide, S3–S5 distinctly longer than wide, S3 the longest sternum, more than 1.5 times as long as wide.

Postabdomen ( Figs 19, 23 ) relatively long and slender. T6 slightly wider than T7, with short thick setae in posterior two-thirds. S6 as wide as long, sparsely setose. T7 moderately long, not extended on ventral side of abdomen, with shallow anteromedial emargination and dense thick setae in posterior two-thirds. S7 longer than broad, dark except lateral and posterior margins ( Fig. 23 ), with long setae in posterior row. T8 simple, transverse, anteriorly poorly delimited, posteromedialy shallowly emarginate, with fine setae in rounded posterior corners. S8 dark, smaller than T8, subcordate, setosity short and dense. T10 very short, tranversely crescent-shaped, dark, microtomentose. S10 also short but wider, paler and longer than T10. Genital chamber ( Figs 21, 22 ) with 3 pairs (2 anterior largely coalesced) of internal twisted sclerites and 1 ventral oval ring-shaped sclerite.Ventral receptacle ( Fig. 22 ) cup-like, weakly slerotised and proximally constricted, with short curved apical projection. Accessory gland on ringed, distally widened duct. Spermathecae 1+1 ( Fig. 20 ) subspherical, with small terminal invagination, minute dark spines in basal half, and with short and broad sclerotised cervix. Cercus ( Fig. 19 ) very short, dark.

Discussion: This member of the M. angustus -group can be easily distinguished from all congeners by the unicolorous brown thorax.Although its slender gonostylus and internal sclerites are similar to those of M. microcercus sp. n., its distiphallic filum and female postabdominal sclerites resemble those of M. signatus sp. n. Therefore, the species seems to be intermediate between these members of the group.Further diagnostic features are: male cercus long and slender; gonostylus bent in the middle; anal opening dorsally strikingly narrowed; saccus setose anterodorsally; female ring-shaped sclerite elongate; female T10 transversely crescent-shaped.

Biology: Adults were collected in June/July and October to December. The species may be associated with indigenous forests. Females dominate the type series (8:1).

Distribution: The species is only known from South Africa.

Figures

Figs 13–18. Margdalops angustus sp. n., male holotype (S. Africa). 13. External genitalia, caudal view. 14. Same, lateral view. 15. Transandrium, caudal view. 16. Hypandrium and associated structures, lateral view. 17. Aedeagal complex, lateral view. 18. Gonostylus, sublateral view (widest extension). Scales: Fig. 18 = 0.05 mm, others = 0.1 mm. For abbreviations see text.

Figs 19–23. Margdalops angustus sp. n., female paratype (S. Africa). 19. Postabdomen, dorsal view. 20. Spermatheca. 21. Internal sclerites, ventral view. 22. Genital chamber with internal sclerites, lateral view. 23. Postabdomen, ventral view. Scales: Figs 19, 23 = 0.1 mm, others = 0.05 mm. For abbreviations see text.

Figs 66–68. Wings of Margdalops species. 66. M. microcercus sp. n., female paratype (Kenya). 67. M. angustus sp. n., female pararype (S. Africa). 68. M. signatus sp. n., female paratype (Kenya). Scale = 0.5 mm.