Parapachycerina Stuckenberg, 1971

Davies, Gregory B. P. & Miller, Raymond M., 2008, Revision of the Afrotropical species of Parapachycerina (Diptera: Lauxaniidae), African Invertebrates 49 (2), pp. 131-131 : 133-139

Parapachycerina Stuckenberg, 1971

Parapachycerina Stuckenberg, 1971: 539 . Type species: Parapachycerina munroi Stuckenberg , by original designation.

Diagnosis:

Small (ca 2.5–5 mm), compact, usually yellow-orange sapromyziform lauxaniids with two reclinate fronto-orbital bristles placed far forwards and close together on postfrons; anterior fronto-orbital bristle small ( Fig. 1 ). Postfrons devoid of setulae (at 50×). Arista plumose; proximal rays longer than height of postpedicel. Postpedicel longer than high, slightly elongated. Ocellar triangle demarcated by dark brown or black spot. Ocellar bristles long, proclinate and subparallel. Prefrons (face) not bulging, without maculations. 0+3 dorsocentral bristles on scutum. No intra-alar bristle. Ctenidium present in some species on profemur. Two ventral mesotibial spurs. Wings hyaline or slightly infuscated. Surstylus unusual; tiny, displaced medially as narrow lamella or flat blade. Immature stages unknown.

In the Afrotropics, Parapachycerina most resembles Neogeomyza Séguy, 1938 (= Micropachycerina Stuckenberg, 1971 ) of East Africa and Madagascar (Miller 1980: 606; see also McAlpine & de Keyzer 1994: 307). Neogeomyza differs from Parapachycerina in having an even smaller anterior fronto-orbital (<0.2× length of posterior fronto-orbital bristle), a larger black ocellar spot, a mildly tumid and translucent prefrons (face), 0+2 dorsocentral bristles, fewer setal rows on scutum, no acrostichal bristles, and an anal lobe in the wing (see Stuckenberg 1971: figs 33, 34). As a generalization, Neogeomyza is also a more gracile and delicate-looking fly than Parapachycerina .

Description:

Colour and pruinescence: Head and thorax usually rich yellow-orange with orange medial mesonotal vitta/e, but dorsal surface of thorax and parts of head strongly infuscated in P. infuscata . Dark brown or black ocellar spot always present. P. infuscata with occiput mostly black, other species have occiput yellow-orange. Pruinescence weak (when viewed at 50×), some silver pruinescence usually visible on anterolateral corner of postfrons, parafacial, and dorsal surface of thorax (oblique lighting sometimes necessary to see pruinosity). Aside from fronto-orbital bristles, postfrons devoid of pruinosity and vestiture (when viewed at 50×), but when viewed with SEM (ca 500– 2000×) postfrons with abundant closely-appressed carinae bearing spicules on medial postfrontal surface, and prefrons with abundant spinules in irregular rows which are not borne on carinae. Eye red or greyish; sparse, simple ommatrichia between facets (only visible with SEM). Maxillary palpus yellow to black. Supracervical area with dusting of silver pruinescence. Haltere yellow or light orange. Legs yellow. Abdomen orange-brown to black, depending on species. Teneral specimens are lightly sclerotized and weakly pigmented, often with collapsed legs and heads.

Head ( Figs 2–9 ): Head higher than long, height:longitudinal length ratio 1.25:1. Head broader than long, transverse width:longitudinal length ratio 1.6:1. Head broader than high, transverse width:height ratio 1.5:1. Two reclinate fronto-orbital bristles, anterior bristle much shorter (ca 0.4× length) than posterior bristle and not as recurved. Fronto-orbital bristles placed far forward on frons, and close together (distance between fronto-orbital bristles is shorter than distance from posterior fronto-orbital to inner vertical seta). Posterior fronto-orbital bristle strong, only slightly shorter than inner vertical seta (ca 0.8× length). Antenna positioned high on head relative to eye (opposite upper third of eye). Arista plumose, rays longer on dorsal surface and progressively shorter distally. Proximal rays of arista are longer than the height of the postpedicel. Postpedicel longer than high (1.6:0.9), tapering gently to moderately pointed apex, shape differing subtly amongst species (most pointed in P. munroi ). Pedicel ca 1/3 length of postpedicel, fan of ca 10 short, proclinate setulae distolaterally, single erect, lateroclinate seta dorsally, and two long, subparallel setae distoventrally (ca 0.7× length of postpedicel). Postfrons broader than high (3:2), gently to moderately curved in lateral profile (not straight); prefrontal (facial)-postfrontal angle obtuse. Prefrons not bulging; prefrontal (facial) carina weak. Orbital plates usually concolorous with remainder of frons and not easily differentiated, except in P. infuscata , where orbital plates usually easily discerned. Inner vertical seta reclinate, and much longer than outer vertical seta (o.v.s. ca 0.4× length of i.v.s.); o.v.s. lateroclinate. Ocellar triangle variable, sides may be equal (e.g. P. bispina ), sides may be longer than base (e.g. P. infuscata ) or base may be longer than sides (e.g. P. munroi ). Ocellar setae strong, semi-erect, proclinate, subparallel and extending to overhang pedicel; ocellar triangle with ca 3 inconspicuous, fugitive setulae behind ocellar setae. Postvertical bristles decussate; intersection of bristles about half-way up the bristles. Postocular setulae in a single row of ca 10 setulae, beginning between o.v.s. and i.v.s.; first 2 or 3 setulae separate from others, slightly longer, inclinate and resembling paravertical setulae. Occiput with 25–35 supracervical setulae. Occipital setulae sparse, restricted to ventrolateral corner of occiput, but extending up towards postocular setulae in some species (e.g. P. bispina ), where forming weak second row behind postocular setulae. Postgena with sparse, scattered setulae. Gena moderately expanded. Proboscis with labellar ‘beak’, and pseudotracheael ‘scoops’ and ‘prongs’ (but preparations crude and further observations needed).

Thorax: 1 pair of acrostichal bristles (setae); 1 humeral (ca 10 weak setulae encircling bristle on callus); 2 notopleurals; 1 presutural; 1 supra-alar; 2 postalars (1 or 2 setulae between bristles), ventral postalar bristle (i.e. bristle closest to the pleurotergite) is considerably (ca 2×) longer than the upper postalar; no intra-alar bristle; 0+3 dorsocentral bristles; setulae rows fairly numerous and rather irregular in pattern, ca 6 longitudinal rows between dorsocentral bristles, ca 8–10 transverse rows behind transverse suture; 1 mesopleural bristle, placed near posterior margin, attended closely by ca 10 short setulae; 1 or 2 sternopleural bristles (if present, anterior bristle weaker and ca 0.7× length of posterior one). Prosternum bare (at 50×). Propleural bristle present, but small and inconspicuous. Posterior pair of bristles on scutellum decussate.

Legs ( Figs 10–15 ): Procoxa has row of 4–6 setae (and a few scattered setulae) on anteroventral margin. Ctenidium on profemur variably present in some species; when present, 4–9 short, stout setulae (rather resembling teeth on a saw). Profemur with posteroventral row of 2 or 3 long setae and posterodorsal row of ca 4 setae. Distoposterior edge of protibia with 2 short spurs, anterior spur ca 2× length of posterior spur. Small (grooming?) comb of ca 10 stout setulae on inner apex of protibia and metatibia (absent on mesotibia).All tibia with dorsal,pre-apical dorsal seta (most robust on mesotibia).Mesocoxa has fan of ca 6 setae (no setulae). Mesofemur with anteromedial row of ca 5 stout, proclinate setae; mesofemur posteriorly largely bare. Mesotibia with 2 short, divergent, distoventral spurs (posterior spur 0.5× length of anterior spur). Metafemur with anterodorsal, preapical, stout, semi-erect seta. Two flattened spurs on inner face of metatibia, anterior one is longer.

Wing: Hyaline or weakly infuscated (in two species). Costa sapromyziform (stout costal setulae terminating 3/4 way between R 2+3 and R 4+5). Costal chaetotaxy Type B2 sensu Hackman & Väisänen (1985: 171). Subcosta and R 1 (Vein 1) closely associated, but diverging somewhat when terminating on costal margin. Veins A 2 and A 1 +CuA 2 parallel, A 2 extending much further towards hind margin of wing (but still falling well short), A 1 +CuA 2 shorter than A 2 .

Abdomen: Chaetation pattern conservative: row of ca 10–15 flat, black setae on posterior margins of syntergite 1+2, T3 and T4, on T5 and T6 these posterior rows become erect. T2 with lateral tufts of short setae. Abdomen tapering posteriorly, T6 slightly less than half (transverse) width of syntergite 1+2.

Male terminalia (e.g. Figs 20–22 of type species; Stuckenberg 1971: figs 91, 92; Sasakawa 2003: fig. 2): Protandrium saddle-shaped (i.e. broad dorsally and narrowing laterally), asetulose and continued ventrally as narrow band (i.e. protandrium is entire). Epandrium displays interspecific variation, but broader laterally than dorsally (cf. protandrium), usually elongated posteriorly as epandrial process (especially in P. bispina and P. lalitra ); sparse cover of scattered vestiture (ca 15 setulae laterally and ca 4 strong setae on medio-posterior edge dorsally). Surstylus small, narrow, laterally compressed, posteriorly hooked lamella or dorsoventrally flattened, blade-like process, fused to inner margin of epandrium; inconspicuous in lateral view, usually resembling small finger projecting posteroventrally. Cerci separate, heavily setulose and partially exposed in lateral view. Inner genitalia small, lightly sclerotised, tightly associated and composed of two ‘systems’: hypandrium + gonopods and aedeagal apodeme + aedeagus; minor additional sclerites include ejaculatory apodeme and subepandrial sclerite. In repose, genitalia point posteriorly, parallel to protandrium and epandrium. No setulae visible on any of genitalic sclerites (at 50×). Hypandrium ventral-most sclerite lying beneath aedeagal apodeme and anterior part of aedeagus; U- or H-shaped, consisting of thin ‘transverse band’ and narrow, lateral arms; hypandrium lacks any medioanterior process.Width of transverse band varies, as does length of lateral arms. Lateral hypandrial arms rise obliquely upwards and posteriorly towards gonopods. At apex of lateral hypandrial arms, hypandrium extends dorsally and anteriorly as thin, weakly sclerotized ‘filaments’ (here termed the ‘dorsal loop’) articulating weakly on anterolateral or anterodorsal edge of aedeagus. Hypandrium can be visualized as square frame of thin sides that has partially folded back on itself. Articulating with posterior apices of lateral hypandrial arms are sheath-like, ensiculate or gently rounded gonopods. Gonopods usually closely ensheath apical part of aedeagus. Aedeagus best visualized as tubular structure (‘aedeagal tube’) comprising two blade-like halves or ‘wings’ joined anteriorly in narrow ‘dorsal arch’ (dorsal-most part of genitalia, cf. hypandrial transverse band); the two halves taper to pointed apices posteriorly where ensheathed by gonopods. Medially, aedeagus is membranous, but this section may be dissolved by strong KOH treatment. Anteriorly, two halves of aedeagus may bulge out in anterolateral flanges. Aedeagal apodeme articulates posteriorly with aedeagus, and is fairly narrow, laterally compressed, Y-shaped, ribbon- or rod-like sclerite, with two short posterior arms. Depending on species, aedeagal apodeme may be longer than aedeagus, approximately equal in length, or slightly shorter. Ejaculatory apodeme is tiny sigmoidal or T-shaped sclerite lying dorsally above bifurcation of aedeagal apodeme. Above posterior sections of aedeagus is subepandrial sclerite, a subrectangular sclerite attached by membranous tissue to posteroventral edge of cercus.

Female terminalia: Unexceptional, short and blunt (not elongated); S9 subrectangular with straight posterior edge and lightly setulose; subanal and supra-anal plates roughly semi-circular; cerci dorsoventrally flattened. Inner genitalia not investigated. Stuckenberg (1971: 590) reported three subspherical spermathecae.

Figures

Fig. 1. Parapachycerina munroi Stuckenberg, type species of genus in lateral view. Length approximately 5 mm.

Figs 2, 3. (2) Dorsal view of head of Parapachycerina munroi Stuckenberg, (3) oblique lateral view of head of P. lalitra sp. n. Note small anterior fronto-orbital bristles (relative to posterior fronto-orbital bristles), short distance separating fronto-orbital bristles, plumose aristae and long ocellar bristles.

Figs 4–7. (4) Postfrons of Parapachycerina munroi Stuckenberg showing abundant carinae medially, (5) medial section of P. munroi postfrons showing spiculate carinae, (6) anterior view of P. munroi head, (7) supracervical setulae on occiput of P. munroi.

Figs 8, 9. (8) Falcate labellar ‘beak’ of Parapachycerina munroi Stuckenberg, (9) labellar ‘scoops’ and ‘prongs’ of P. munroi.

Figs 10–15. (10) Profemur of Parapachycerina infuscata sp. n. with ctenidium (comb) of short, stout setulae on anteroventral edge, (11) profemur of P. munroi Stuckenberg without ctenidium, (12) posterior view of P. munroi profemur showing dorsal and ventral rows of setae, (13) presumed grooming comb on distal edge of P. munroi protibia, (14) distoventral mesotibial spurs of P. munroi, (15) sapromyziform costa of P. infuscata sp. n.

Figs 20–24. Inner ơ genitalia: (20–22) P. munroi Stuckenberg in dorsal (20), oblique dorsal (21), and ventral (22) views; (23) P. bispina sp. n. and (24) P. infuscata sp. n. in dorsal view.