Ocypodomyia africana, Pont, 2006

Pont, Adrian C., 2006, Ocypodomyia gen. n. from the seashores of the Afrotropical region (Diptera: Muscidae: Limnophorini), African Invertebrates 47, pp. 321-334 : 329-334

Ocypodomyia africana sp. n.

Figs 2 , 6 , 9 , 17–23

Etymology: The species name refers to the distribution of the species.

Description:

Male.

Head: Ground-colour black. Eyes bare. Entire head except for eyes and antennae silverywhite pruinose. Frons broad, narrowing from vertex towards middle and then broadening again to lunula, at lunula 0.4 of head-width at this point, at middle 0.45 of head-width at this point ( Fig. 2 ). Ocellar setae short; inner and outer verticals short, the outer 2/3 as long as the inner and half as long as an ocellar seta. Row of post-ocular setulae with a partial or complete second row. Frons uniform in appearance, with a differentiation into fronto-orbital plates, frontal vitta and ocellar triangle almost undetectable; 3 or 4 pairs of short frontal setulae from lunula to level of anterior ocellus, these directed forwards and slightly inwards, and above them with a pair of equally short reclinate orbital setulae; 1 or 2 short setulae outside them on fronto-orbital plate. Profrons high, so that the face and antennae are unusually long ( Figs 17, 18 ), the distance from profrons to ocellar seta equal to 0.8 of the distance from profrons to vibrissa.Antennae black, the apical part of pedicel sometimes orange, the flagellomere with grey pruinosity visible from some angles. Flagellomere very long, in lateral view reaching almost to level of vibrissa. Arista sometimes partly orange, bare. Parafacial broad, at narrowest point wider than width of flagellomere. Face narrow and very sunken, with a low vertical carina along upper part at least, and lower anterior part of head much enlarged as a result. Lower facial margin narrow, the vibrissae unusually close together. Facial ridges bare. Mouth-margin reaching forwards beyond level of profrons. Vibrissae strong, crossed. Gena broad, below lowest eye-margin equal to a quarter of an eye-depth; bare except for a row of setae along lower margin. Proboscis short, slender, the prementum glossy dark brown. Palpus dark brown, slender.

Thorax: Ground-colour black. Wholly whitish, almost silvery-white dusted, with dark bristle dots at the base of most dorsal setae, in 1ơ with an inconspicuous small greydusted spot on each side between 1st postsutural dorsocentral and suture, otherwise scutum, scutellum and pleura unmarked. Spiracles white. All setae short. Acrostichal setulae 2- to 3-serial at first, 3- to 4-serial at suture, with a very weak prescutellar pair of setae; 2+3 dorsocentrals; 1+2 intra-alars, the postsutural setae very fine and weak; 1+1 supra-alars; 2 postpronotals; prealar absent; 2 postalars. Prosternum with 2 or several pairs of setulae on margin. Notopleuron with 2 setae, otherwise bare. Proepisternum with 1 strong and 1 moderate seta; proepisternal depression with 1 or 2 fine setulae or bare. Proepimeron with 1 seta and 1–3 tiny setulae, all directed upwards.Anepisternum with 4 setae in posterior row, and a strong setula in upper anterior corner. Anepimeron bare; 1+2 katepisternals, upper posterior one twice as long as the other two, lower one much closer to upper posterior than to upper anterior seta. Meron with or without 1 or 2 short setulae below spiracle. Posterior spiracle without setulae on margin. Katatergite pilose. Anatergite bare. Scutellum with 1 pair of sub-basal lateral and 1 pair of apical setae; disc rather densely setulose, with up to 29 setulae; lateral margins and ventral surface bare.

Legs: Coxae dark; trochanters orange; femora narrowly orange-yellow at base and at tip, otherwise dark and grey dusted; tibiae brownish, broadly orange-yellow in basal part to mainly orange-yellow; tarsi brown. Without modifications in structure or setation. Fore femur with a posteroventral row, the setae weaker in basal half. Fore tibia without a submedian posterior seta; 1 dorsal and 1 very short posteroventral apical setae. Mid femur with some short posteroventral setae in basal half, otherwise without ventral setae; with a submedian anterior seta, and some shorter setae basad of this; 0 anterior and 2 posterior preapical setae. Mid tibia with 2 posterior setae, without anterodorsals or ventrals. Hind femur with 2–4 anteroventral setae in apical half, otherwise only with setulae on this surface; posteroventral surface with several short setae in basal half; with an anterodorsal row, the setae becoming more dorsal towards apex; 1 dorsal and 0 posterodorsal preapical seta. Hind tibia with 1 anterodorsal and 1 anteroventral setae, without posterodorsal; 1 dorsal but no anterodorsal preapical seta; 1 anteroventral but no posteroventral apical seta. Hind tarsomere 1 without a ventral setula.

Wing: Clear, the surface entirely covered with microtrichia and appearing rather milky. Basicosta and tegula yellow. Veins yellow. Costa continuing round wing-tip to the apex of vein M, the costal spine tiny. Veins bare, except for costa and vein R 4+5 where 1 or 2 dorsal and ventral setulae may be present at base or absent. Subcosta running in a somewhat sinuous course from humeral cross-vein to costa, not in a smooth curve. Cross-vein r–m below or slightly beyond the point where vein R 1 enters costa. Cross-vein dm–cu upright, straight or (usually) rather sinuous. Vein M running straight to wing-margin, not inclined forwards. Vein A 1 extending over halfway from its base to wing-margin. Calypters white, including margins. Lower calypter of the Phaonia - type and projecting well beyond upper one. Haltere with the stem orange and the knob pale yellow.

Abdomen: Ground-colour black. Dorsal surface white, almost silvery-white dusted; tergites 3 and 4 each with a pair of small black subtriangular spots, well separated by dust from each other and from the side margins, those on tergite 3 touching fore-margin of the tergite, those on tergite 4 occupying just over half of tergal length; these spots sometimes reduced, the spots on tergite 3 smaller and poorly defined and those on tergite 4 absent, these spots rarely even absent. Tergites without setae, except for tergite 5 which has 2 or 3 pairs of lateral discals and a row of marginals. Ventral part of tergites and sternites whitish dusted, but in posterior view the sternites and much of tergites 1+2 to 4 dull to broadly darkened. Sternite 1 narrow, with several fine setulae on each side. Sternite 5 with the lobes broad, pale ( Fig. 19 ).

Genitalia: Cercal plate deeply cleft dorsally and ventrally ( Fig. 22 ). Surstyli simple ( Fig. 23 ). Hypandrium with a pair of large rounded bulbous prolongations ventrally. Phallapodeme and epiphallus well developed. Praegonite large, spade-like; postgonite curved, without setulae. Aedeagus long and slender, the tip membranous, without trace of any armature.

Measurements: Length of body, 3.2–4.6 mm. Length of wing, 2.7–3.6 mm.

Female.

Differs from the male as follows:

Head: ( Figs 20, 21 ): Frons broadening gradually and evenly from vertex to lunula. The setulae slightly stronger. Frons at lunula 0.45 of head-width at this point. Ocellar and vertical setae slightly longer, outer vertical not shorter than ocellar. 2 or 3 pairs of frontal setae, and above them with 2 pairs of orbitals, the lower one proclinate, the upper one directed backwards and slightly outwards, and outside them on the frontoorbital plate with 2–4 short proclinate setulae. Profrons not so high and therefore less angular, the distance from profrons to ocellar tubercle 0.7 the distance from profrons to vibrissa ( Fig. 20 ). Antennal flagellomere (and face) much shorter, 2.5 times as long as wide. Parafacial broader, 1.5 times as wide as width of flagellomere in profile. Lower anterior part of head not so enlarged. Gena rather narrower, below lowest eye-margin equal to only 0.4 of the depth of the eye.

Thorax: Scutum unmarked.

Legs: Mid femur with the posteroventral setae reduced to setulae. Hind femur bare ventrally except for 1 or 2 anteroventrals before apex.

Wing: Cross-vein dm–cu straight.

Abdomen: Tergites 3 and 4 without dark spots but sometimes with weak shadows where the spots of the ơ would be. Ventral surface sometimes more grey. Tergite 5 with the marginal setae weak, only 2 pairs.

Ovipositor ( Fig. 9 ): Tergite 6 as two broad plates; sternite 6 as a broad median rod. Tergite 7 as a pair of strongly sclerotised rods, each with a pair of small platelets at tip; sternite 7 absent, represented by a pair of bristle-dots. Tergite 8 as a pair of bars running down the side of the ovipositor; sternite 8 as a pair of small hind-marginal platelets. Membrane between segments 7 and 8 with tiny spicules. Epiproct, hypoproct and cerci setose, without spines. 3 spherical spermathecae.

Measurements: Length of body, 4.2–5.0 mm. Length of wing, 3.0–4.0 mm.

Variation: The silvery pruinosity on frontal vitta and on parts of the scutum is tinged with yellow in one of the Gambian ^.

Other features that show variation are:

Setulae on vein R 4+5 are present in 1ơ 4^from Angola and 1ơ from Senegal; absent in 1ơ from Angola, 7ơ 4^from Gambia, 2ơ 2^from Senegal.

Setulae on proepisternal depression are present in 1ơ from Angola, 3ơ from Gambia, 2ơ from Senegal; absent in all ^^except two from Gambia.

Setulae on meron are absent in 1ơ 2^from Senegal and 3ơ 1^from Gambia.

Sternite 1 setulae are absent in 1^from Senegal.

Holotype: ơ ANGOLA: Cuanza R. mouth, 40 miles S Luanda, i.1972, B. Stuckenberg ( NMSA).

Paratypes: ANGOLA: same locality data as holotype, 1ơ 4^(1ơ 3^NMSA, 1^BMNH) . GAMBIA: Tanji Bird Reserve , in Ocypode burrow on beach, 21.xi.1993, C.E. Dyte, 7ơ 4^( NMWC) . SENEGAL: Plage Somone , dans terriers de crabe [in crab burrows], 4.x.1961, no collector given, 3ơ 2^(2ơ 2^MNHN, 1ơ BMNH) .

Discussion: Of the two Senegal females, one is somewhat damaged (squashed) and has several sand grains adhering to the tip of the abdomen; it may have been collected whilst in the act of oviposition. The second female and one of the females from Gambia have the ptilinal sac still largely extruded, with several grains of sand stuck to it; this certainly suggests adult eclosion from a puparium buried in the sand.

Distribution: Known from seashore localities in Angola, Gambia and Senegal.

Figures

Figs 1, 2. Male frons, dorsal view: (1) Ocypodomyia stuckenbergi sp. n. (Madagascar, Sainte-Luce); (2) Ocypodomyia africana sp. n. (Angola, Cuanza R.). Scale bar = 1 mm.

Figs 3–6. Male genitalia of species of Ocypodomyia gen. n.: (3–5) O. stuckenbergi sp. n. (Madagascar, Ambohitantely): (3) aedeagus, lateral view, (4) hypandrium, anterior view, (5) aedeagus, ventral view; (6) O. africana sp. n. (Senegal, Plage Somone), aedeagus, lateral view. Abbreviations: a – praegonite, b – postgonite, c – phallapodeme, d – epiphallus, e – distiphallus, h – hypandrium, hp – paired hypandrial prolongations. Scale bar = 0.5 mm.

Figs 7–9. Ovipositors of species of Ocypodomyia gen. n.: (7, 8) O. stuckenbergi sp. n. (Madagascar, Sainte- Luce): (7) dorsal view, (8) ventral view, sternite 8; (9) O. africana sp. n. (Angola, Cuanza R.), ventral view, sternites 6, 7. Abbreviations: tg – tergite, st – sternite. Scale bar = 1 mm.

Figs 17–19. Ocypodomyia africana sp. n. (17) male head, lateral view (Angola, Cuenza R.); (18) SEM of male head, frontal view (Gambia, Tanji Bird Reserve); (19) male sternite 5, dorsal view (Senegal, Plage Somone). Scale bars = 0.5 mm.

Figs 20, 21. Female head of Ocypodomyia africana sp. n. (Angola, Cuanza R.): (20) head, lateral view; (21) frons, dorsal view. Scale bar = 0.5 mm.

Figs 22, 23. Male genitalia of Ocypodomyia africana sp. n. (Senegal, Plage Somone): (22) hypopygium, dorsal view; (23) hypopygium, lateral view. Scale bar = 0.5 mm.