Tongamya stuckenbergi Irwin & Wiegmann, 2001

Irwin, Michael E. & Wiegmann, Brian M., 2001, A review of the southern African genus Tongamya (Diptera: Asiloidea: Mydidae: Megascelinae), with a molecular assessment of the phylogenetic placement of Tongamya and the Megascelinae, African Invertebrates 42, pp. 225-253 : 241-247

Tongamya stuckenbergi Irwin & Wiegmann , sp. n.

Habitus illustrations of male ( Fig. 2) and female ( Fig. 3)

Etiology: This species is named for Brian R. Stuckenberg, mentor and life-long friend of MEI , in honour of a lifetime of meritorious contributions to African and World Dipterology.

Type Material: Male holotype ( MEI 109134), two male paratypes ( MEI 109136; MEI

089484), and one female paratype ( MEI 109135) from the same locality and collection date (see material examined). The females from Angola ( MEI 116621) and Etosha ( MEI 108188) are included in the material examined below, but are not included as type material; upon discovery of males of these populations, they may prove to be a distinct species.

Distribution: The type material is from the westernmost edge of the Kalahari Desert in Namibia ( Fig. 4). Two females that we currently place in this taxon are from northern Namibia (Etosha) and southwestern Angola ( Fig. 13). (Note: Slight morphological differences separate the two female specimens ( Angola and Namibia) from the material at the type locality. These two females extend the range delimited by the type material considerably northward; the differences between the type population and that of the northern specimens are discussed above (see ‘Diagnoses of the species within Tongamya ’). Males of these northern populations are unknown.)

Material Examined: ANGOLA, Ambundos Province, Benguela District, 1 female, 48 km S. Benguela [-13.0113º, +13.4039º], 21-IV-1971, H. D. Brown, ( MEI 116621, NMSA). NAMIBIA, 1 female, Etosha National Park, Mushara [-18.6167º, +16.8833º], 14-X-1986 to 15-XI-1986, E. Griffin, ( MEI 108188, SMWN); 3 males 1 female, Otjinene District, 2 km S. Otjisume Farm [-21.3117, +19.3222], 27-XI-1996, hand netted, M. E. Irwin, 1400 m, ( MEI 109134 [holotype], SMWN; MEI 109136 [paratype], NMSA; MEI 089484 [paratype] [thorax macerated for DNA], NCSU, [remainder of specimen], MEIC; MEI 109135 [paratype], NMSA).

Description: The following description is, for the most part, based on the holotype male ( MEI 109134).The internal male terminalia are described from a dissected male paratype ( MEI 089484). Where appropriate within the description, morphological variation based on the other male paratype ( MEI 109136) is provided. The single topotypical female specimen ( MEI 109135) is described below the male description; comparisons are made with the two more northern females ( MEI 108188 and MEI 116621), tentatively placed within this taxon.

Male ( Fig. 2): Body length, excluding antennae, 11.0 mm ( MEI 109134); 11.4 mm ( MEI 109136).

Head: Head large ( Figs 2, 6), wider above, narrowing below ( Fig. 12). Ocellar tubercle visible in frontal view( Fig.6),formed by a transversely raised, rounded ridge.Frons narrowly triangular ( Fig. 6). Pruinescence light yellowish-grey overall. Antennae short, attached at lower third of head ( Fig. 10); ratio of scape:pedicel:flagellum, 4:2:9. Apex of flagellum subpyriform with off-centered fovea; stylus one-segmented. Compound eyes occupying most of head ( Fig. 12); eye facets divided at level of antennae; lower facets smaller ( Fig. 6). Anterior ocellus enlarged; posterior ocelli one-third as broad and far removed from anterior ocellus ( Fig. 6). Occiput with short, scattered, outwardly radiating pale blond setae. Mouthparts greatly reduced; medially placed labium directed upward, cleft apically, forming a pair of elongate labial palps. Elongate, thinly pointed, spine-like structure, formed by union of two robust, convergent setae, directed outward and upward.Small, one-segmented maxillary palp flanking lateral edges of prementum.

Thorax: Tanish yellow, including legs with well defined dark brown patches on upper portion of antepronotum, outer lateral edges of basisternum, flanking anteriomesal edge of postalar callus, lateral edges of scutellum, anterolateral margins of postnotum, anteroventral portion of anepisternum, outer portion of anterior basalare, ventral most axillary sclerite, anterior and posterior edges of sclerite supporting anterior spiracle, anterior half of subalar sclerite, anterior edge of sclerite supporting posterior spiracle, lower half of both katepisternum and meron, anterobasal and apical margins of fore- and middle coxae, anterolateral face of hind coxa, dorso-apical tips of hind femora, and apical tarsomeres of all legs. Fine, sparse, tan pile confined to pronotum, outer lateral half of basisternum, and anterior face of forecoxa. Pile in a broad lateral sweep from postpronotal lobe to attachment of wing; parallel, longitudinal vitae of slightly shorter pile along flanks of mesonotum. Postpronotal lobes enlarged, tanish-yellow, with thin dusting of tan pruinescence and thin, dense, pale tan hairs. Presternum bare, with deep, ventro-medial groove. Scutellum deep, strongly transverse, yellow; dorsally flattened, mottled with tan pruinescence. Mesopleuron bare except pruinescence on ventral halves of katepisternum and meron, posterodorsal thirds of katepimeron, katatergite, outer lateral half of basisternum, and anterior face of middle coxa. Halter 1.4 mm in length; stem tan, knob white.

Wings ( Figs 2, 3): Length 7.2 mm, of paratype 8.0 mm, 3 times longer than wide. Wing membrane transversely wrinkled, cloudy white; alula narrow. R 2+3, R 4 and R 5 +M 1+2 ending in R 1, joining R 1 almost at costa; CuA 2 +M 3 curving upward to end in R 5 +M 1+2 .. Costa weakening gradually from base of junction with Sc to wing tip. Costa, subcosta, R 1, CuA 2 and, to a lesser extent, R 2+3 and M 1 pale brown; remaining veins almost colourless. Vein CuA 1 curves upward to join M 3; m 3 cell closed.

Legs ( Fig. 2): Surfaces of legs covered with dense, short, recumbent, yellow-tan hairs; hind tibial anteroventral setae short. Fore- and middle coxae with erect, sparse, yellow pile on anterior surface; hind coxa with similar pile on outer lateral surface. Hind legs conspicuously longer and thicker. Fore- and middle tibiae swollen apically; hind tibia greatly thickened apically, broadening to 2 times as wide at apex. Fore- and middle basitarsus thin, elongate, about 6 times longer than wide; hind basitarsus stout, about 2.5 times longer than wide, almost uniformly thick throughout, slightly narrower apically and almost as thick as apex of hind tibia.

Abdomen ( Fig. 2): Elongate, tapering, 2.5 times longer than length of thorax. Tergite 1 swollen laterally, forming single broad, raised, tan callus across posterior half. Prominent circular spiracle imbedded within each posterodorsal corner of sternite 1. Spiracles of segments 3–7 set laterally in pleural membranes; sclerotised brown rings surround spiracular openings. Abdomen greasy in appearance, lacking pruinescence, with short, appressed, sparsely spaced pale yellow hairs, except for callus and terminalia, which have denser, longer hairs. T2–T7 dark, shiny brown dorsally, pale tan at lateral margins and as narrow wedges along outer posterior margins of T3–T7. Sternites and pleural areas pale tan; anteromedial portion of S2–S3 each with a small, dark brown, inverted ‘V’ marking, its arms coalesce into irregularly shaped blotches in similar positions on S4–S7.

Male terminalia: Erect, yellow on preserved specimen. Tergite 8 ( Fig. 14) lacking vestiture, arched, medially narrow, anteromesally heavily brown pigmented, posteromesally weakly pigmented. Sternite 8 broad, deep, shovel-shaped, weakly pigmented, without vestiture. Epandrium ( Fig. 21) divided by broad median biconcave cleft into 2 subtriangular sclerites anteriorly connected by sclerotised strap; brown with thin, sparse, pale tan hairs over posteriodorsal four-fifths. Elongate, flattened, semiforked plate (herein termed ‘ventral plate of gonopod’) lying beneath enlarged gonopod ( Figs. 14, 22), heretofore assumed to be hypandrium in Tongamya ( Stuckenberg 1966; Yeates & Irwin 1996) and Megascelus ( Artigas 1970 1973). Our interpretation is that hypandrium may be a small, scoop-shaped, well sclerotised plate lying anterior to ventral plate of gonopod. If true, hypandrium bare, broadly scoop-shaped, overlapping ventral plate of gonopod ( Fig. 22), supporting a pair of thin, strongly sclerotised arms that extend laterally and dorsally, and attach to lateral fold where gonopods and epandrium hinge ( Fig. 14). Gonopod consisting of large, paired, robust gonocoxites ( Fig. 14) and ventral plate of gonopod; gonostyli lost. Brown stripe along dorsolateral edge of each gonocoxite. Aedeagus consists of a slightly upcurved tube, widely open anteriorly and posteriorly, with a strong, dorsocentral, vertically oriented, rigid extension to base of hypoproct ( Figs 14, 29). Distiphallus narrowing and flattening along apical third, flaring somewhat at apex ( Figs. 29, 30). Ejaculatory apodeme small ( Fig. 29). Lateral ejaculatory process ( Sinclair et al. 1993) prominent, horseshoe shaped. Cerci form a shallowly roofed, bilobed sclerite ( Fig. 21). Hypoproct horizontally flattened, thin, extending to apex of cerci ( Fig. 14). Basally, hypoproct curves ventrad, uniting solidly with dorsocentral portion of aedeagus.

Female ( MEI 109135): Length, excluding antennae, 15.8 mm. Similar to male but larger. Head proportionally smaller, 1.5 times wider than high. In lateral view, head narrow above, widest at level of antennae, narrowing below ( Fig. 10). Frons wider than high, shallowly concave, with patchy, sparse, greyish-white pruinescence around anterior ocellus; with numerous, vertically oriented, subparallel, irregular grooves over frons and vertex ( Fig. 8). Vertex yellow-tan with vertical swelling laterally ( Fig. 8) (area between ocellar tubercle and compound eye of Etosha and Angola specimens not swollen); vertex elevated on sides above eye margins, forming a central, raised, tan ocellar tubercle (more prominent in Etosha andAngola specimens).Genae slightly swollen, cream-white, with thin white pruinescence. Compound eyes dichoptic, bare, small, undivided; facets uniform in size ( Fig.10).Anterior ocellus enlarged. Posterior ocelli smaller, situated laterally on ocellar tubercle, visible in frontal view ( Fig. 8). Wing length 7.8 mm, width 2.6 mm. Hind tibiae and basitarsi not swollen ( Fig. 3). Abdomen greasy in appearance, dark reddish-brown; swollen over first five segments (widest at segment 3), tapering rapidly at segment 6, with segments 7, 8 and genitalia cylindrical and half as thick as segment 3 ( Fig. 3); white marking on posterolateral corners of T2–T4 ( Fig. 3).

Female terminalia: Segment 8 telescoped within segment 7. Spiracles inset at weakly pigmented posterior area of segment 8; spiracular opening smaller than spiracles of other segments; characterised by thin trachea extending inward for a considerable distance, then expanding greatly within segment ( Fig. 31) (termed ‘auxiliary spiracle’ by McAlpine et al. 1981). Tergite 8 (T8) elongate, ‘U’ shaped in cross section, tapering to shovel-shaped towards apex. Anterodorsal third relatively smooth and bare; rest of dorsum with short, sparse hairs. Sternite 8 (S8) similar in shape to T8 but shorter, narrower, ventrally smooth in texture with scattered, short, erect hairs. Posteriorly truncate, slightly infolded, forming shallow invagination. Tergite 9+10 (T9+10) heavily sclerotised, comprised of upper, anterior component (T9) and two ventrolateral, posterior sclerites (acanthophorites, T10) ( Figs 32, 35). T9 dome-shaped ( Fig. 35), divided into 2 narrowly fused dorsolateral sclerites ( Fig. 32). Sternite 9 (furca, S9) ( Fig. 32) framed by longitudinal, opposing, membrane-spanded struts. Spermathecal elements ( Fig. 32) arise from gonopore as a common spermathecal duct. Two large, irregularly ovalshaped, weakly sclerotised spermathecae attach by thin spermathecal ducts to midpoint of common spermathecal duct, which extends as a twisted duct terminating in a spermathecal sac ( Fig. 32) ( Winterton et al. 1999). Two elongate, slightly bulging accessory glands attach by thin ducts originating from 2 minute, parallel apertures at posterior end of furcal membrane ( Fig. 32). T10 (acanthophorites) ( Figs 32, 35) paired sclerites, curving and widening ventrad, each baring circlet of 6–7 strong, flat, blunt spines ( Fig. 35). Hypoproct at posterior margin of furca, extends posteromesally as a small, weakly sclerotised, long-haired structure, terminating between paired lateral cerci ( Fig. 32). Cerci sausage-shaped, thinly sclerotised, longhaired, lying laterally within and conforming to inner basal curve of paired acanthophorites ( Fig. 35).