Moegistorhynchus longirostris ( Wiedemann, 1819 )

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 : 13-17

Moegistorhynchus longirostris ( Wiedemann, 1819)

( Figs 1.1–1.3 , 4.1–4.9 , 9.5–9.6 , 12 )

Nemestrina longirostris Wiedemann, 1819: 13 .

Moegistorhynchus longirostris ; Bezzi, 1924: 189; Bernardi, 1973: 269; Bowden, 1980: 374.

Type locality. Cape of Good Hope , Western Cape (assumed) .

Type material ( holotype in ZMUC): South Africa: Western Cape: HOLOTYPE: ♂: “ ♂ ”; “Mus. / Westerm.”; “TYPE” [red card]; “ N. longirostris / Wied. / Cape Good Hope / Octb. 1817” [handwritten in Wiedemann’s hand]. Specimen associated with holotype: ♀: “ ♀ ”; “Mus. / Westerm.”; “TYPE” [red card]. The holotype and associated specimen are both in excellent condition. Given that the original description refers to a male only, the female is not considered to be part of the type series and is not labelled as a paratype. The holotype is appropriately labelled.

Notes on the holotype and associated specimen. We located the male holotype of Nemestrina longirostris Wiedemann, 1819 , in ZMUC. The holotype is appropriately labelled in Wiedemann’s hand and is also appropriately labelled “Mus. Westerman”. It is labelled “ Cape Good Hope” as noted (in Latin ) in the original description. The holotype had previously been labelled as “ TYPE ” on red card.

Other material: Western Cape: 2♂ 2♀, Atlantis, Silverstream , 33.5284 18.4454, 1 December 2017, Timo van der Niet , Feeding [on] P. longicaule ( NMSA) ; 1♀, 5 km N Bloubergstrand, 16 November 1975, H. Geertsema ( SANC); 1♂, Cape Peninsula, Miss Johns ( SAMC); 31♂ 16♀, Graafwater , C.P., October 1947, Mus. Exp. ( SAMC); 1♂, Graafwater, C.P., October 1947, Mus. Exp. ( NMSA); 1♂, Lamberts Bay , 1 October 2008, L. McCleod ( SAMC); 10♂ 5♀, Leipoldtville, Elands Bay , C.P., October 1947, Mus. Exp. ( SAMC); 1♂, Mamre, 3318 CB, Silverstroomstrand , 26 November 1978, V.B. Whitehead ( SAMC); 1♂, “ Montague ”, 1902, F.C. Purcell ( SAMC); 1♀, Mowbray, November 1940, Miss Johns ( SAMC); 1♀, 10 km NE Muizenberg, 3418AB, 28 November 1981, B.R. Stuckenberg, coastal macchia ( NMSA); 1♂, Pella Mission St [ation], 20 October 2011, A. Morton ( SAMC); 2♂, Silverstroom, 6 November 1995, on Pelargonium ( SAMC) ; 3♂, Silverstroomstrand, 29 October 1993, on Pelargonium ( SAMC) ; 6♂ 5♀, Strandfontein, False Bay , 1 November 1960 ( SAMC); 1♂, West Coast National Park , 33°10’56’’S 18°03’45’’E, 30 m, 11 September 2001, J.G.H. & A. Londt, sandy areas, bushes, flowers ( NMSA); 1♂, West Coast National Park, 10 October 2010, A. Morton ( SAMC); 1♂, Yzerfontein, 22 October 1993, Lapeirousia ( SAMC) ; 1♂ 1♀, Yzerfontein, 33°20’S 18°10’E, 1 November 1992, J. Manning, on Lapeirousia anceps ( NMSA) ; 1♀, Yzerfontein, September 1960 ( SAMC); 1♂, Yzerfontein (rt side of road), 30 October 1992, on Lapeirousia anceps ( SAMC) ; 1♀, Zeekoevlei , Cape Town, 34.0614° S, 18.5152° E, 31 Oct. 2023, D.A. Barraclough, Visiting Pelargonium in garden ( SAMC). Northern Cape: 2♂ 1♀, 20 km E. Hondeklip Bay, 5 September 2008, L. McCleod ( SAMC); 1♂, 12 km E. Hondeklipbaai, 9 September 2006, L. McCleod ( SAMC); 1♂, 8 km E. Hondeklip Bay, 21 August 2007, L. McCleod ( SAMC); 1♀, Namaqua National Park, S30.411581 E17.415748, 29 August 2019, A. Melin & J.F. Colville, visiting Pelargonium praemorsum [DNA: 3 legs; RHS] ( SAMC); 2♀, Spektakelberg Pass [about 25 km W of Springbok], 11 September 1993, Lapeirousia fabricii ( NMSA) ; 1♂ 2♀, 7 km WNW of Wallekraal on road to Hondeklip Bay, 14–16 September 1992, F.W. and S.K. Gess, visiting cream long tubed fls ( Iridaceae ), flower: Engysiphon longitubus Lewis ( AMGS) .

Diagnosis. Postpedicel mostly dark, but with striking paler basal annulation; style with two basal segments. Proboscis elongate to remarkably elongate, typically 2.0–5.5 x body length. Postalar callus smooth over entire surface. Wing with striking transparent or hyaline markings, such areas typically not an opaque creamy white. Second abdominal tergite dark medially and submedially, never entirely silver pruinescent across its width. Abdominal dorsum (especially in male) with posterolateral sections of T3 to T5 with dense and prominent clustering of (usually) dark pile on posterolateral extremities.

Redescription (both sexes). Body length 11.66–17.73 mm ( Fig. 4.1 ); wing length 11.54–19.90 mm; proboscis length 32 to 83 mm and possibly up to 90 mm (see Barraclough & Slotow 2010). Head ( Figs 4.3–4.4 ): colouring yellow-brown to dark brown to black with scape and pedicel mostly yellow or yellow-brown. Postpedicel mostly dark brown to black but usually with striking or obvious yellow/orange basal annulation on both surfaces, although this can be variably developed or reduced. Male with anterior ocellus and posterior ocelli separated by transverse groove; anterior and posterior ocelli all about equidistant apart and therefore forming the three corners of an equilateral triangle, although posterior ocelli may be further apart; long black (pale posteriorly) pile between anterior ocellus and posterior ocelli or a mix of pale and dark pile or (rarely) all dark pile. Frons with elongate yellow pile (sometimes partly black posteriorly) over much of surface. Style of flagellum with two short black basal segments, subequal in length, second segment slightly longer or shorter. Proboscis strikingly elongate, length 2.0–5.5 x body length. Thorax ( Figs 4.5–4.6 ): scutum pale, medium to dark brown and only ground colour beneath median and submedian vittae very dark (this black) although this mostly obscured by dense silver pruinescence; sometimes appearing yellow-brown in medial area at two-thirds distance between anterior margin and scuto-scutellar suture, this colouring may extend to scuto-scutellar suture. Paired median silver pruinescent vittae extend from anterior margin to two-thirds distance to scuto-scutellar suture or entire distance; at two-thirds position an inverted V-shaped extension of dark pruinescence extending backwards to scutellum. Scutellum very densely and broadly silver pruinescent anterolaterally and along posterior margin just posterior to disc; sometimes this pruinescence evident around entire margin. Pile on scutum sometimes a mixture of yellow and black, but usually mostly yellow; moderately elongate and profuse but largely sparse to absent (notably absent in Strandfontein specimens) on posterior half (although notably present on postalar calli and scutellum as sometimes sparse elongate hairs with more black hairs sometimes evident in female). Postalar callus lacking a noticeable acute cuticular protrusion near middle. Legs: mostly medium to darker brown or dark brown, but sometimes a paler yellow-brown. Fore femur with relatively elongate backwardly directed pale pile, this sometimes reaching up to two-fifths femur length. Mid and hind femora with sparse ventral pile (similarly coloured) along basal two-fifths to three-quarters of mid femur (sometimes very sparse or barely present) and along basal one- to two-thirds of hind femur, although sometimes very sparse or virtually absent. Wing ( Fig. 4.7 ): relatively slender, length more than 3.5 x maximum width. Infuscation a medium to darker brown to grey, but sometimes with yellowish tinges. Patterning irregular and distributed over much of wing as in figure, although hyaline areas often dominate posteriorly; hyaline areas clearly distinguished and separate from brown colouring. CuP with one complete crossvein (rarely half complete) with appendix often present. Abdomen ( Figs 4.8–4.9 ): relatively slender or moderately so and often broader than width of thorax. Ground colour mostly dark yellow-brown or dark brown to black and sometimes with hints of orange, although sometimes extensively orange; sometimes partly yellow on several sternites. T1 entirely dark brown to black with obvious silver pruinescence along anterior margin, except at midline (usually) or medially and (postero)laterally; pile dense and short, mostly yellow or white. T2 dark brown to black medially and submedially (may be faded in older specimens), with obvious silver pruinescence laterally; pile short, sometimes over entire surface. T3 largely medium to dark brown to black but sometimes orange-tinged or orange posteriorly or even laterally and medially, and with paired silver pruinescence/markings (irregularly transversely positioned) on anterior half to two-thirds, these markings may extend to lateral margins, meaning that silver pruinescence is confluent with silver pruinescence along lateral margins although posterior margin also often appearing silver pruinescent; pile sparse (may be mostly absent in female), pale and relatively short to moderately long on anterior one- to two-thirds or on most of surface, but with strikingly dense cluster of golden pile anterolaterally (may be shorter, less dense and yellowish) and dense (sometimes somewhat sparser) cluster of striking elongate black pile at posterolateral extremities (sometimes partly or mostly pale); in female clustering of pile along lateral margins may be reduced. T4 similar except paired silver pruinescent central markings roundish and sometimes mostly separated by brown ground colour from lateral silver pruinescence; pile typically present over much of surface and pale (sparse and mostly short to absent in female), sometimes dense and elongate and yellow or golden along entire posterior margin (except laterally), longest pile reaching up to two-thirds length of lateral margin, lateral margin with short (moderately) dense golden pile anteriorly (may be sparse and yellowish) and typically elongate and striking cluster of black pile posterolaterally (sometimes partly golden). T5 similarly patterned; pile sometimes moderately long on anterior two-thirds, absent along posterior margin and distributed along lateral margins as on T4 (mostly absent in female, except laterally); anterior cluster of golden pile may be barely visible and posterior cluster may be a mixture of golden and black or all golden. T6 with median brown area but otherwise silver pruinescent; pile short and sparse. Sternites yellow-brown to medium or dark brown; pile notably elongate and white on S3. Male postabdomen ( Figs 9.5–9.6 ): epandrium moderately developed to very slender in dorsal view, maximum width notably broader than length, with small to moderately developed apical notch above cerci, apicolateral extremities broadly rounded to flattened in lateral view. Gonostylus with variously developed vestiture along inner medial margin, and presenting as two lobes: a slender but well-developed inner lobe and a short to very short and apically rounded outer lobe, inner lobe with apical region strongly narrowed. Inner gonocoxal process mostly straight and very slender, narrowly rounded apically, apical region with or without marginal teeth. Phallus apex typically falling just short of gonostylus apices in ventral view, without obvious marginal dentition (minute dentition sometimes visible).

Relationships and distribution ( Fig. 12 ). Moegistorhynchus longirostris is most similar to M. brevirostris , although it has a very much longer proboscis. As with M. brevirostris , it is a lowland species; however, it appears to be more widespread ( Barraclough & Slotow 2010) and is more frequently encountered in the field, in particular in the southern parts of its range. It is distributed across a stretch of more than 700 km from the southern parts of the Western Cape around Cape Town northwards to the area around Port Nolloth in the Northern Cape ( Fig. 12 ). Note that there is a single record from “Montague”. This old specimen (collected in 1902 and deposited in SAMC) is almost certainly mislabelled. Montagu is about 180 km east of Cape Town in the Little Karoo. Bequaert (1935: 494), for example, referred to this specimen in his important review of the genus. We have not seen any specimens at these latitudes from outside of the Cape Town area. Note that many of the localities of M. longirostris are listed in Table 1 ( Barraclough & Slotow 2010: 402), together with co-ordinates, proboscis length (range and mean), and bioregion (name, protection status and conservation status). Vegetation type: Atlantis Sand Fynbos (FFd4); Cape Flats Dune Strandveld (FS6); Lambert’s Bay Strandveld (FS1); Langebaan Dune Strandveld (FS5); Leipoldtville Sand Fynbos (FFd2); Namaqualand Granite Renosterveld (FRg1); Peninsula Sandstone Fynbos (FFs9); Peninsula Shale Renosterveld (FRs10); Namaqualand Heuweltjieveld (SKn4); Namaqualand Klipkoppe Shrubland (SKn1); Richtersveld Coastal Duneveld (SKs1).

Discussion. Although variable in body colouring (especially of the abdominal dorsum), size, the distribution and length of pile on the abdominal dorsum, and in proboscis length across its extensive lowland range, it seems that M. longirostris is not a species complex. We have examined more than 100 specimens and have dissected representative males from across the geographical range and there is no significant variation in the form of the male terminalia, apart from a variably developed epandrium which can range from a slender to moderately developed appearance in dorsal view. We therefore consider M. longirostris to be a single morphologically variable species. The species has been collected between 21 August and 1 December.

More intensive collecting of M. longirostris in the Northern Cape is required. We have not, for example, been able to study males (only females available) of specimens from Namaqua National Park and Spektakelberg Pass. These specimens have a significantly shorter proboscis length (45–50 mm) than specimens from nearby Hondeklip Bay (proboscis length reaching 70 mm).

Although not listed under ‘Other material’, we have seen images (sent to us by email) of three specimens of M. longirostris (one male and two females) that were collected from 8 km E. of Port Nolloth in the Northern Cape on 1 October 2009. The material was collected by Dr Torsten Dikow and Dr J. Londt and is deposited in the National Museum of Natural History ( USNM) in Washington, D.C. It was not feasible to loan this material, which represents the northernmost limit of the species range. Given that Port Nolloth is only about 100 km from the Namibian border, M. longirostris may eventually be found to fringe into the Succulent Karoo parts of southern Namibia.

Despite very extensive urbanisation and development in the Cape Town Metropolitan Municipality, it is gratifying to know that M. longirostris is still collected in the region. We have seen images on iNaturalist ( Table 2) that can reliably identify the species from the Zeekoeivlei area (6 November 2022; 18 October 2023); Strandfontein area (5 November 2022); Rocklands between Strandfontein and Wolfgat Nature Reserve (5 October 2023); Witzands Aquifer Nature Reserve, NE Koeberg Nature Reserve, 10, 12 & 15 October 2023), and Blaauwberg Nature Reserve (4 November 2012, 11 October 2023). Furthermore, a locality near Mamre, in the far north of the Municipality, has been a favoured collecting and observation spot that has been used by pollination biology researchers over the last 20 years.

Figures

FIGURE 1 (1.1–1.3). Photographs of adult Moegistorhynchus longirostris in the field: 1. Taking up nectar from a species of Pelargonium (photo credit: Louis van Wyk). 2. Visiting an atypical host plant, the red flowers of the bird-pollinated Babiana hirsuta (Lam.) Goldblatt & J.C.Manning (see, also, figure 5 of Pauw et al. 2009) (Photo credit: Mayur Prag). 3. Characteristic hovering posture before entering the elongated flower of Lapeirousia anceps (L.f.) Ker Gawl.; note the dense covering of pollen on the thorax and abdomen from this host plant (Photo credit: Colin Patterson-Jones).

FIGURE 4 (4.1–4.4). Moegistorhynchus longirostris (Wiedemann, 1821) (male). 1. Whole body, lateral view. 2. Label data. 3–4. Head. 3. Frontal view. 4. Oblique lateral view, showing detail of antennae with orange basal annulation of postpedicel arrowed.

FIGURE 9 (9.1–9.6). Male terminalia: dorsal (left) and ventral (right) views. 1–2. Moegistorhynchus braunsi (annotated). Abbreviations: cerc—cercus; epand—epandrium; goncx—gonocoxite; gonst—gonostylus; hypd—hypandrium; ph—phallus. Note elongate tuft of pile on hypd. 3–4. Moegistorhynchus brevirostris. 5–6. Moegistorhynchus longirostris.

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).