Tetrameringia stuckenbergi, Barraclough, 2002

Barraclough, D. A., 2002, A new species of Tetrameringia McAlpine (Diptera: Schizophora: Clusiidae) from Malawi, the third species from theAfrotropical Region, African Invertebrates 43, pp. 5-10 : 7-10

Tetrameringia stuckenbergi sp. n.

( Figs 1–3 )

Etymology: Named for Dr B. R. Stuckenberg, one of the collectors of the type series, and in recognition of his pioneering work on the African Clusiidae .

Holotype male: MALAWI: ‘ MALAWI Ntchisi Forest / reserve 1334Ac 1500m / Londt & Stuckenberg / 3–4.xii.1980 Montane / forest & woodland’; ‘ HOLOTYPE male / Tetrameringia / stuckenbergi sp. n. / Det. D. Barraclough, 2001’. In NMSA; in good condition.

Description: Male: Dimensions (in mm): Head/Thorax length 2.3–2.5 [2.5]; wing length 3.0–3.3 [3.3].

Colour/Pollinosity: Head ( Fig. 1 ): Frons shining, dark brown to black at vertex and between ocelli, and dark over about posterior two-thirds, grading into yellow or pale yellow-brown on anterior one-third. Antenna yellowish, but arista distinctly darker brown. Parafacial mainly yellowish, somewhat darker ventrally. Face yellowish on upper two-thirds, but pale to dark brown on ventral third. Gena entirely yellowish. Outer margin of face, parafacials and gena with sparse silver pollinosity evident at certain angles only. Occiput shining dark brown to black on upper half, strikingly paler (yellowish) on ventral half. Proboscis yellowish, palpus yellow-brown.

Thorax mostly dark brown, but cream to yellow on propleuron and around anterior spiracle, and entire section of pleuron between upper margin of sternopleuron and haltere insertion; mesonotum yellowish medially and sublaterally, outer extent of pale ground colour coinciding roughly with dorsocentral row or just lateral to it, commencing near anterior margin between humeral calli and just posterior to humeral bristle insertions, although pale ground colour sometimes reaching medial section of anterior mesonotum margin; scutellum mostly dark or partly yellow-brown on basal half (particularly basal corners), with sparse silver pollinosity. Haltere mostly yellowish.

Legs: Fore leg mostly yellowish, but tibia pale brown (except at extreme base and apex). Mid leg entirely yellowish. Hind leg mostly yellowish to yellow-brown, basal half of tibia sometimes partly brownish.

Wing: Membrane hyaline basally, otherwise smoky brown over much of anterior two-thirds; largely hyaline posterior to cubital vein ( Fig. 2 ).

Abdomen: Tergites dark brown to black, except tip of abdominal terminalia conspicuously yellow-brown.

Head ( Fig. 1 ): Frons slightly convergent towards antennae, subequal or slightly shorter at mid-length (from anterior margin of anterior ocellus to ptilinal suture) to width; frons width 36–37 % of head width. Head width subequal to length of mesonotum. Head height 76–80 % of head width. Gena extremely narrow, at mid-length 6.5–7.0 % of eye height. Postgenal region not ventrally prominent, with posteroventrally directed bristle. Face narrow, 12–15 % of head width, higher than broad, sclerotised along entire height. Arista short-haired, longest hairs about twice width of arista at base. Spaces between orbital bristles about in proportion 2.0: 4.0: 4.5–5.0, anterior and second bristles subequal in length and strength, about three-quarters length and strength of posterior 2 pairs. Outer vertical bristle about three-quarters length and strength of inner vertical. Postvertical bristles subequal in length to posterior pair of orbitals, ocellars also subequal in length. Frons with sparse, pale, fine setulae. Vibrissa single, well developed, two-thirds to four-fifths length of arista.

Thorax: Two bristles on propleural region, the anterior moderately developed and the posterior weak. Mesopleuron with 1 bristle and with setulae scattered over posterior one-third. One sternopleural bristle, disc of sternopleuron sometimes with a few upwardly directed setulae. One strong humeral bristle; 2 notopleurals, anterior one longer, and posterior one slightly to noticeably shorter than humeral; 1 presutural, noticeably weaker than humeral, and half to three-quarters length; 1 long supra-alar; 1 very long anterior postalar, posterior postalar weak, noticeably less than half length and strength of anterior bristle; 0 + 2 dorsocentrals, anterior one one-quarter to one-third length of posterior one and inserted at about threefifths distance between transverse and scutoscutellar sutures; 1 weak prescutellar acrostichal bristle, similar in length to anterior dorsocentral. Mesonotum with numerous stiff, suberect, setulae, these usually longer towards scutoscutellar suture. Scutellum with pair of very long (subequal in length or slightly shorter than posterior postalar) divergent, apical bristles, also 1 pair subapical marginal bristles and pair of cruciate discal scutellars in virtually the same transverse line, all subequal in length but about one-third length and strength of apicals. Prosternum with up to 3 dark setulae on each side.

Wing ( Fig. 2 ): Venation as figured; r-m crossvein close to middle of discal cell; fourth vein index 2.7–3.1.

Legs: Fore femur with prominent row of strong, black, posteroventral bristles on much of length, reaching up to two-thirds depth of femur. Fore tibia with very small preapical bristle. Mid femur with similar posteroventral bristles, albeit length half femur depth. Mid tibia without pre-apical bristle, but with strong apico-ventral spur. Hind femur without differentiated posteroventral bristles. Hind tibia without dorsal pre-apical bristle, and sometimes with weak apico-ventral spur.

Abdomen: Tergites with profuse, dark setulae over much of surface, these longer laterally; marginal bristles just discernible.

Male terminalia ( Fig. 3 ): Cercus short, reduced, dorsoventrally flattened, with a conspicuous long ventral setula. Surstylus broad basally, then abruptly narrowed and then gradually broadened to smoothly rounded apex. Only 1 pair of short, ovoid parameres, with indistinct apical setulae. Sternite 6 slender along entire height, narrowed and lanceolate dorsally. Aedeagus flexed to the right as in aethiopica .

Paratypes: 2 males, same data as holotype. In NMSA .

Discussion: Tetrameringia stuckenbergi apparently has no close relatives in the afrotropical fauna, including the numerous undescribed species from Madagascar. The Madagascan species T. distoma has strikingly distinct thoracic colouration. T. stuckenbergi is readily distinguished from the only named African species, T. aethiopica (see species key above). T. stuckenbergi is currently known only from the moist afromontane Ntchisi Forest in Malawi. This forest is in the upper part of the rift valley escarpment overlooking Lake Malawi, in a site exposed to heavy rains and dense mists in summer.

Figures

Fig. 1. Tetrameringia stuckenbergi sp. n., head profile, showing details of patterning and all vestiture.

Fig. 2. Tetrameringia stuckenbergi sp. n., wing, showing patterning and venation.

Fig. 3. Tetrameringia stuckenbergi sp. n., profile view of male terminalia, showing shape of T9, cercus and surstylus.