Moegistorhynchus manningi Barraclough & Colville, 2024

Barraclough, David A. & Colville, Jonathan F., 2024, Revision of the endemic South African genus Moegistorhynchus Macquart (Diptera: Nemestrinidae), with a species key, description of three new species and comments on pollination biology and biogeography, Zootaxa 5519 (1), pp. 1-37 : 17-20

Moegistorhynchus manningi Barraclough & Colville sp. nov.

( Figs 5.1–5.10 , 12 )

Type locality. Hottentot Holland Mountains (between the eastern Cape Town suburbs of Somerset West and Gordon’s Bay in the west and the Elgin valley in the east), Western Cape province .

Type material (holotype in SAMC and paratype in NMSA): South Africa: Western Cape: HOLOTYPE: ♂: “Hot Holl. Mtns / East side 4000 ft ”; [reverse side of label] “ K. H. Barnard / Jan 1933 ”. The holotype is in good condition . PARATYPE: ♀: “Villiersdorp, Stettynsberg / 33°50’S 19°20’E / Date: 12.i.1999 / Coll: J. Manning ” .

Etymology. The species name manningi celebrates the collector of the female paratype, Dr John Manning (Compton Herbarium, SANBI). Dr Manning first referred to this species (then undescribed) in the literature. Dr Manning has made a profound contribution to our understanding of the role of long-proboscid Nemestrinidae in South African pollination biology over more than 25 years.

Diagnosis. Style with one basal segment. Wing with paler areas a distinctive opaque creamy white and not transparent or hyaline. Postalar callus with a small sharply pointed cuticular projection near its middle (unique to this species).

Description (both sexes). Body length 13.92–14.40 mm ( Fig. 5.1 ); wing length 14.30–14.40 mm; proboscis length 21.41–24.00 mm. Head ( Figs 5.3–5.4 ): colouring a mixture of yellow-brown to dark brown to black and scape and pedicel medium brown (densely yellow pruinescent in female). Postpedicel mostly black, but with restricted orange ground colouring on inner basal surface. Male with anterior ocellus and posterior ocelli separated by deep transverse groove; anterior ocellus set far forward and therefore further from the posterior ocelli than the posterior ocelli are from each other. Frons with elongate yellow pile; pile largely absent medially. Style of flagellum with one presumably fused and relatively elongate basal segment. Proboscis short, length slightly longer than body length and ranging up to 1.5 x body length. Thorax ( Figs 5.5, 5.6, 5.10 ): scutum medium to dark brown to black, although paler (medium to dark brown) on postalar calli and adjacent to wing insertion and on disc of scutellum (here may be yellow-brown). Paired median silver pruinescent vittae extend from anterior margin to scuto-scutellar suture, but interrupted by brown colouring/pruinescence at two-thirds distance between anterior margin and scuto-scutellar suture. Scutellum densely silver pruinescent over lateral parts and sparsely brown to golden pruinescent along posterior margin just posterior to disc. Pile on scutum a mixture of yellow (predominant) and a few black hairs, short but profuse; largely sparse to absent on posterior half (although obviously present on postalar calli and disc of scutellum and otherwise as very sparse, short and yellow hairs). Middle of postalar callus with small but obvious acutely pointed cuticular projection at about middle (apex may be black-tinged) (see Fig. 5.10 ). Legs: fore femur yellow, legs otherwise yellow-brown to medium brown. Fore femur with elongate posterodorsally directed yellow pile reaching about one-third femur length. Mid and hind femora with rather sparse yellow pile ventrally along basal two-thirds of mid femur and basal one-quarter to one-third of hind femur. Wing ( Fig. 5.7 ): relatively slender in male only, length about 3.0 x maximum width (broader in female, length about 2,6 x maximum width). Infuscation medium to dark brown, but darker on anterior half. Patterning distributed over much of wing, as in figure; no transparent hyaline areas, instead these areas largely replaced by an opaque creamy white appearance (these areas larger and more extensive/conspicuous in female). CuP sometimes with short incomplete crossvein, this not extending to wing margin. Abdomen ( Figs 5.8–5.9 ): relatively robust and broad in male, much broader than maximum width of thorax; much more slender in female (same width as thorax). Ground colour brown to black on tergites, but sternites often partly yellow. T1 entirely dark brown to black and silver pruinescence completely lacking; pile dense and short, mostly yellow to white. T2 densely silver pruinescent across entire width (except appearing brown posteromedially, although this may be membrane); pile largely absent. T3 largely medium brown, but with small paired medial silver pruinescent markings (elongate-ovoid and transversely positioned) on anterior half, and extending to lateral margins in female; narrowly silver pruinescent along most of posterior margin; pile relatively sparse and short (longer and more profuse in female), yellow to white, mostly restricted to anterior half (but may be absent from elongate-ovoid markings), longest hairs at most half length of T3 lateral margins. T4 similarly coloured and patterned, but silver pruinescent posterior margin much more extensive, with this pruinescence merging broadly with lateral margins; ground colour paler posteriorly; pile typically sparse and short and present anteriorly only, this yellow, longest hairs reaching half length of T4 lateral margin (pile very sparse and short in female). T5 even more extensively silver pruinescent, with small round brown areas medially; pile barely evident. T6 medium to yellow-brown with single median brown area. Sternites yellow-brown to medium brown to black; pile longer and white on S4.

Relationships and distribution ( Fig. 12 ). Moegistorhynchus manningi does not appear to have close affinity with any of the other Moegistorhynchus species. It appears to be a montane species and is known from only two localities. Vegetation type: Hawequas Sandstone Fynbos (FFs10); Kogelberg Sandstone Fynbos (FFs11).

Discussion. We have been aware of this species for more than 15 years. Unfortunately, the first collected specimen (the female paratype) is in poor condition, with the wings crumpled along much of their length and the right wing apex torn, most of the legs are damaged or missing, and the abdomen is detached and glued back on at its base. It was impossible to describe the species as new based on material in such poor condition, especially since the male was unknown. Fortunately, in 2022, we discovered a conspecific male in good condition in SAMC. The second author has visited the Stettynsberg locality, but unfortunately no additional specimens were collected.

Moegistorhynchus manningi was collected pollinating the rare Gladiolus rhodanthus J.C. Manning & Goldblatt in the Stettynsberg (see Manning et al. 1999: 218). These authors also noted that it pollinated Erica praecox , Pelargonium radiatum and Watsonia paucifolia at this locality. Gladiolus rhodanthus deposits pollen on the dorsal surface of the thorax, W. paucifolia on the top of the head, E. praecox on the face and P. radiatum on the underside of the thorax ( Manning et al. 1999: 218). The SANBI Red List of South African Plants (http://redlist.sanbi.org/species. php?species=1549-608) notes that Gladiolus rhodanthus has a distribution of less than 5 km 2 at an altitude of 1800 metres.

Given that this species is known only from the male holotype and a female paratype (in poor condition), the male postabdomen was not dissected. Dissection of the holotype could damage the proboscis, which is closely appressed to the abdominal apex.

Note that this remarkable new species has three features which are unique in the genus: wing with paler areas all a distinctive opaque creamy white and these not transparent or hyaline; postalar callus with a small sharply pointed cuticular projection near its middle; and style of antennal flagellum with only one basal segment. These may be autapomorphies.

Figures

FIGURE 5 (5.1–5.4). Moegistorhynchus manningi sp. nov. (male holotype). 1. Whole body, lateral view. 2. Label data. 3– 4. Head. 3. Frontal view. 4. Oblique lateral view, showing detail of antennae with style with only one short basal segment (arrowed).

FIGURE 12. Distribution of the seven species of Moegistorhynchus across the coastal and montane areas of the Fynbos and Succulent Karoo Biomes (includes confirmed iNaturalist records to February 2024).