Margdalops microcercus, 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 : 6-11

Margdalops microcercus sp. n.

( Figs 1–12 , 66 )

Type material: Holotype male, labelled: ‘ KENYA: Mt. ElgonLodge , 1–6.XI.83, A. Freidberg’ ( TAUI, genit. prep.) . Paratypes: KENYA: 1 female, same data as holotype ( TAUI) . UGANDA: 1 male 1 female (with apex of abdomen lost), Mbarara, 15.xi.1934, F. W. Edwards ( BMNH). All paratypes with genit. prep .

Etymology: The name ‘ microcercus ’ refers to the unusually small male cercus of this species.

Description: Male.

Total body length: 1.78–2.06 mm. Body brown and yellow.

Head: Slightly to distinctly longer than high. Frons pattern similar to that of M. angustus , but frontal triangle reaching to anterior two-thirds of frons; anterior medial stripe like frontal triangle dull (not velvety) brown. Orbit shining brown. Ocellar triangle slightly convex, shiny. Face yellow-white; gena dirty white and silvery white microtomentose with narrow, pale brown ventral margin; postgena pale brown. Mouthparts whitish yellow. Chaetotaxy as in M. venustus , but pvt longer and crossed; vti almost as long as vte and crossed medially; oc less proclinate; 1–2 pairs of microsetulae in front of frontal triangle; vi as long as anterior strong ors; 2 subvibrissae (anterior shorter and weaker, posterior about two-fifths length of vi). Eye with longest diameter about 1.4–1.5 times as long as shortest one. Gena higher than in relatives; its minimum depth 0.1 times as long as shortest eye diameter. Antenna with ochreous scape, pedicel and anterodorsal part at base of arista, remainder of 1st flagellomere yellowish white. Arista about twice as long as antenna, longer ciliate than in other Margdalops species.

Thorax: Dorsally brown, ventrally yellow. Mesoscutum anteromedially with 2 elongate, sparsely silvery grey microtomentose spots between dorsocentral lines. Humeral and notopleural areas lighter brown than mesoscutum. Pleural area with brown dorsal band, wider anteriorly (covering entire propleuron), narrower posteriorly; remainder of pleura yellow. Chaetotaxy as in M. venustus , but setae generally weaker, anterior dc shorter and inserted somewhat nearer to posterior dc, and anterior stpl longer. Scutellum slightly convex dorsally. Legs yellow. Pedal chaetotaxies as in M. venustus ; f 3 with a posteroventral row of 17–18 setae, 5 of which (in distal two-fifths) are short and thickened.Wing pattern ( Fig. 66 ) as in M. angustus , but R 4+5 almost straight, very slightly convergent to M distally, and CuA 1 slightly bent. Discal (dm) cell wide and r-m as in M. angustus . Wing measurements: length 1.94–2.32 mm; width 0.51–0.68 mm, Cs 3: Cs 4 = 2.84–2.93, r-m/dm-cu: dm-cu = 3.51–3.72. Haltere brown with darker knob.

Abdomen: Brown; preabdominal terga similar to those of M. angustus , but sterna markedly broader. S2 as long as wide, S3 and S4 slightly longer than wide, S5 wider than long, wider than S4 and slightly emarginate posteromedially. T6 distinct although very weakly sclerotised, transversely band-like. S6–S8 as in M. angustus , S7 somewhat longer.

Genitalia: Epandrium ( Figs 4, 5 ) moderately long, short setose, with dorsolateral setae thicker, dorsomedial pair longest.Anal opening small, rounded triangular, dorsomedially narrowed. Cercus smallest of all congeners, narrow but well sclerotised and its ventral end tapered ( Figs 4–5 ). Medandrium ( Fig. 4 ) also narrow and relatively high. Gonostylus ( Figs 5, 6 ) slender, gradually tapered towards apex, similar to that of M. angustus , but less bent and with blunt apex; its outer side with a few setulae among distinct micropubescence being restricted to posterior two-thirds; inner side with scattered setae. Hypandrium not very robust, simple ( Fig. 3 ); transandrium almost straight ( Fig. 1 ); basal membrane medially with small transverse tubercles. Pregonite ( Fig. 3 ) with reduced number of setae (only 1 long and 1 small seta in anterior position). Postgonite ( Fig. 3 ) slender, tapered in distal half, with apex bent anteriorly, without setulae; besides finely striated membrane there is a dark plate-shaped sclerite attached to anteroproximal end of postgonite. Aedeagal part of folding apparatus with small lenticular tubercles; connecting sclerite ( Fig. 2 ) slender, barely sclerotised. Aedeagal complex ( Fig. 2 ) with slender phallapodeme having shortly bifurcate base and laterally dilated apex. Saccus of distiphallus unusually small, membranous, but with a pair of relatively long internal sclerites and with spines and spinulae, particularly numerous at apex. Filum short and robust, formed by 2 proximally fused, distally diverging and rifted sclerites connected by membrane, hence apex broad and lobate ( Fig. 2 ). Ejacapodeme larger and darker than in the M. venustus group, with slender subapical projection ( Fig. 2 ).

Female differs from male as follows:

Total body length 2.02–2.46 mm.

Face, gena and antenna somewhat darker (yellow on gena to ochreous-brown on pedicel). Humeral area sometimes ochreous. f 3 posteroventrally finely setulose. Wing measurements: length 2.24–2.66 mm; width 0.65–0.79 mm, Cs 3: Cs 4 = 2.79–3.14, r-m/ dm-cu: dm-cu = 3.73–3.77. Abdomen with T2–T5 wider and more transverse. S2–S5 wider than in M. angustus , S3–S5 slightly or hardly (S5) longer than wide.

Postabdomen ( Figs 7–8 ) relatively long and narrow. T6 slightly wider than T7, with short thick setae in posterior half. S6 relatively narrow, as wide as S5 but slightly shorter, sparsely setose. T7 long, extended on ventral side of abdomen (even enclosing 7th spiracles), with anteromedial emargination, a dark transverse lateral stripe on each side, and thick setae in posterior half. S7 narrow, elongately ligulate, but posteriorly dilated ( Fig. 8 ), with longer setae in posterior half. T8 simple transverse, with posteromedial emargination and fine setae in rounded posterior corners. S8 dark, slightly smaller than T8, subcordate, shortly setulose. T10, short, transverse, dark, unpigmented posteromedially, with microtomentum restricted to medial area. S10 slightly wider, paler and longer than T10. Internal sclerotisation of genital chamber ( Figs 10, 11 ), composed of 3 pairs of crooked, partly coalesced sclerites and of a ventral ring-shaped sclerite ( Fig. 10 ). Ventral receptacle ( Fig. 11 ) subconical to flask-shaped, proximally ringed and with apical s-shaped vermicular projection. Spermathecae 1+1 ( Figs 9, 12 ) subspherical, one slightly larger than the other, with small dark spines on slightly projected base around duct insertion, and with long (longer than spermatheca) sclerotised cervix gradually merging into membranous duct. Cercus ( Fig. 7 ) very short and dark. Discussion: M. microcercus sp. n. forms, together with M. angustus sp. n. and M. signatus sp. n., the M. angustus -group. Its monophyly is demonstrated by 4 character states, viz. ejacapodeme enlarged; filum of distiphallus compact, with paired sclerites fused and apically provided with teeth or processes; female internal ring-shaped sclerite well developed; female cercus very short and dark. The inter-relationships of these species has not been resolved (see below). M. microcercus sp. n. is considered the most primitive species of Margdalops because it retains a number of plesiomorphies unknown in other congeners (e.g. small cercus, narrow medandrium, large basal sclerite of postgonite). On the other hand, its female postabdomen displays several advanced features (modified, narrowly ligulate S7; expanded T7 enclosing spiracles; long cervix of spermatheca). Besides these diagnostic characters, the species can also be recognised by having 2 subvibrissae (otherwise only in M. signatus sp. n.), the pregonite with only anterior setae, a reduced saccus, and by a characteristic filum of the distiphallus.

Biology: All type specimens (2 males 2 females) were collected in November.

Distribution: Kenya, Uganda.

Figures

Figs 1–6. Margdalops microcercus sp. n., male holotype (Kenya). 1. Transandrium, caudal view. 2. Aedeagal complex, lateral view. 3. Hypandrium and associated structures, lateral view. 4. External genitalia, caudal view. 5. Same, lateral view. 6. Gonostylus, sublateral view (widest extension). Scales: Fig. 6 = 0.05 mm, others = 0.1 mm. For abbreviations see text.

Figs 7–12. Margdalops microcercus sp. n., female paratype (Kenya). 7. Postabdomen, dorsal view. 8. Same, ventral view. 9. Spermatheca. 10. Internal sclerites, ventral view. 11. Genital chamber with internal sclerites, lateral view. 12. Spermatheca. Scales: Figs 9, 10 = 0.05 mm, others = 0.1 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.