Moegistorhynchus perplexus Bequaert, 1935

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 : 20-24

Moegistorhynchus perplexus Bequaert, 1935

( Figs 6.1–6.9 , 10.1–10.2 , 11.1 , 12 )

Moegistorhynchus perplexus Bequaert, 1935: 498 ; Bernardi, 1973: 269; Bowden, 1980: 374.

Type locality. Clanwilliam , Western Cape province .

Type material ( holotype in NMSA): South Africa: Western Cape: HOLOTYPE: ♀: “ ClanWilliam / IX-1928 / Dr. Brauns. ”; “ Moegistorhynchus / perplexus Bequ. / ♀ / HOLOTYPE No: 34. [all in red]”; “ J. G. Bequaert det., 1933: / Moegistorhynchus / perplexus / holotype J Beq.”. The holotype is in fairly good condition, except that the apical part of the left wing is torn and much of the abdominal dorsum is greasy.

Other material: South Africa: Western Cape: 1♂ 4♀, Dasklip Pass, near Porterville , 18 November 1991, Dr J.B. Ball ( SAMC); 3♀, Groot Winterhoek, 1017 m, S34.10185 E18.3669, A. Melin & J.F. Colville, 11 November 2017, abundant visiting Codonorhiza falcata and Geissorhiza confusa ( SAMC) ; 1♂, same data but Wachendorfia paniculata [JWC_GW_07: DNA: 3 legs; RHS] ( SAMC); 1♂, Gydo Mtn, 24 km NE of P. Alfred Ham. [ Prince Alfred Hamlet ] 3319AB, Londt & Quickelberge, 21 November 1986, 1150 m, rocky area/Proteas ( NMSA); 2♀, Gydoberg, S33.207481 E19.365436, 30 December 2023, 1652 m, J.F. Colville, visiting Pelargonium alpinum [ JFC _ Gydo_2023: DNA: 3 legs; RHS] ( SAMC); 1♂, Piquetberg [= Piketberg ] Mountain , 17 October 2009, L. McCloud ( SAMC); 1♀, Picketberg [= Piketberg ], 32.79856 18.66592, Florent Grenier ( NMSA).

Diagnosis. Postpedicel mostly dark; style with two basal segments. Proboscis strikingly elongate, typically more than twice body length. Postalar callus smooth over entire surface. Wing with clear-cut transparent or hyaline markings, such areas never an opaque creamy white. Second abdominal tergite almost entirely silvery pruinescent across its width. Posterolateral sections of T3 and T4 typically with relatively dense fringe of dark pile. Epandrium prominently divided into two obvious lobes dorsally and with very broad and extensive medial notch; gonostylus narrowed apically and with sharply pointed apex.

Redescription (both sexes). Body length 11.30–17.04 mm ( Fig. 6.1 ); wing length 10.90–20.21 mm; proboscis length 24.59–55.31 mm. Head ( Figs 6.3–6.4 ): colouring mostly yellow to dark brown to black, with scape and pedicel notably yellow-brown or medium brown. Postpedicel mostly darker (brown to black), but sometimes dark orange or yellow basally. Male with anterior ocellus and posterior ocelli separated by deep transverse groove; anterior ocellus closer to posterior ocelli than posterior ocelli are to each other, therefore delimiting a compressed triangle. Frons with elongate yellow pile, this absent medially. Style of flagellum with two short basal segments, these subequal in length or second segment ranging up to 2.0 x length of first segment; second segment may be difficult to discern. Proboscis elongate, length 2.00–2.75 x body length. Thorax ( Figs 6.5–6.6 ): scutum yellow to medium or dark brown and ground colour beneath median and submedian vittae black, sometimes paler (brown) ground colour evident only laterally and on scutellum. Paired median silver pruinescent vittae extend from anterior margin to two-thirds distance to scuto-scutellar suture in female (remaining posterior section a pale to dark orange or yellow-brown), but may extend entire distance in male; in male sometimes with transversely positioned dark brown pruinescence over median pruinescent vittae at two-thirds distance between anterior margin and scuto-scutellar suture. Scutellum variably silver pruinescent around much of margin or posteriorly only. Pile on scutum yellow but some black hairs on posterior half, short but profuse; largely sparse to absent on posterior half (although present here on postalar calli and disc of scutellum and along posterior midline area). Postalar callus smooth over entire surface. Legs: almost entirely yellow ranging to pale, medium or even dark brown. Fore femur with relatively elongate backwardly directed whitish pile, this sometimes reaching one-quarter to one-third femur length. Mid and hind femora with sparse ventral pile (similarly coloured) along basal half to two-thirds of mid femur and along basal one-quarter to half of hind femur. Wing ( Fig. 6.7 ): slender to very slender, length reaching 3.5 x maximum width or more. Infuscation an indistinct dark smoky brown, sometimes a darker brown. Patterning rather irregular and distributed over much of wing as in figure; hyaline areas not strikingly distinguished or delineated. CuP with one short crossvein (sometimes lacking from one wing), obviously incomplete and does not reach hind margin. Abdomen ( Figs 6.8–6.9 ): somewhat compact, width broader than maximum width of thorax, although sometimes broader in female. Ground colour very varied, ranging from dark brown to black to dark orange. T1 entirely dark and silver pruinescence completely lacking or barely visible; pile dense and short, mostly white or yellow with some black hairs. T2 typically densely silver pruinescent across entire width (except sometimes posteromedially, but this may be membrane); pile largely inconspicuous, but white pile sometimes evident laterally. T3 largely dark brown to black to orange, but with silver pruinescence/markings on anterior half as paired elongate-oval medial areas (transversely directed), these areas with dark colour between and/or around them and this sometimes along anterior margin; silver pruinescence sometimes occurring laterally and along posterior margin; pile moderately short and sparse over anterior one-third to four-fifths (especially medially), whitish to pale yellow but black hairs evident on posterior half, pile elongate along anterior margin and sometimes dense posterolaterally (black pile), longest anteriorly, this length about half length of T3 lateral margins. T4 similarly coloured and patterned; silver pruinescence sometimes evident laterally and along posterior margin; pile typically short and sparse and mostly black, more profuse posterolaterally, this dark brown to black, longest hairs one-third to half length of T4 lateral margin. T5 medium to dark brown to orange, but with darker brown colouring anteromedially, and silver pruinescent markings similar to those on T4; pile usually dark, elongate and restricted to lateral margins. T6 medium brown to orange and silver pruinescent, darker medially; pile elongate along lateral margins. Sternites usually mostly yellow-brown to dark brown to black (partly yellow), but often darker in female; pile moderately elongate and white on S3 and S4. Male postabdomen ( Figs 9.1–9.2 ): epandrium very well developed in dorsal view, maximum width somewhat broader than length, strikingly divided into two major lobes and with broad and very conspicuous medial notch, apicolateral extremities very broadly rounded in lateral view. Gonostylus with vestiture over medial surface, notably slender in appearance, apical region sharply pointed apically and inwardly curved. Inner gonocoxal process not sharply pointed apically, here rather bluntly tapered, apical region with obvious marginal teeth, relatively straight and not arched at mid-length. Phallus apex about coincident with or falling short of gonostylus apices in ventral view, arrow-like apically with obvious dentate subapical margins.

Relationships and distribution ( Fig. 12 ). Moegistorhynchus perplexus is most similar to M. braunsi (distinguished mainly by colour differences and features of the male terminalia), and also appears to be a montane species. Moegistorhynchus perplexus is a montane species and has been collected mainly from mountain catchment areas in the Western Cape between Prince Alfred Hamlet in the south and Clanwilliam in the north. Vegetation type: Olifants Sandstone Fynbos (FFs3); Piketberg Sandstone Fynbos (FFs6); Swartruggens Quartzite Fynbos (FFq2); Winterhoek Sandstone Fynbos (FFs5); Citrusdal Vygieveld (SKk7).

Discussion. It should be noted that there is considerable colour variation (head, scutum, legs and abdominal dorsum) and we suspect that M. perplexus represents a cluster of species, in particular given that the holotype is fairly distinct from all other specimens and given that no other material is known from the type locality (but see discussion below). However, the male terminalia from at least three different localities have been dissected and there is no significant morphological variation. These issues considered, a study of the species over its entire range using molecular markers could potentially reveal interesting results.

The female holotype of M. perplexus is unusually small, its proboscis is relatively short (2.0 x body length) compared to other specimens (2.00–2.75 x body length), the postpedicel is paler than many of the other specimens, and the legs pale (yellow). Furthermore, it was collected at Clanwilliam which lies at an altitude of about 100 m (other material is largely montane). We were initially concerned that it was not conspecific with the other M. perplexus material, but believe that it is a small and somewhat pallid specimen. The holotype is 96 years old and appears to have faded significantly since its description in 1935. We also note that there is size and proboscis length variation in a species with close affinity, M. braunsi .. Notable body size variation is also evident in the series of M. perplexus collected at Dasklip Pass, near Porterville. We illustrated the female holotype ( Figs 6.1–6.9 ) so that the identity of the species is clear should it prove to be a species complex in future.

Manning (2004) first published on the pollination biology of M. perplexus . At Middelberg Pass (near Citrusdal) he noted M. perplexus pollinating the ribbon pincushion Leucospermum tottum var. tottum . We have not seen this material, but based on the photographs in the publication, it is highly likely to be M. perplexus . Manning noted three other plants likely to be pollinated by these flies in the area: Geissorhiza confusa and G. cedarmontana and, a little way off, lxia paniculata (all Iridaceae ).

Newman (2017) referred to the pollination of the threatened Erica junonia var. junonia by M. perplexus in the Skurweberg mountains near Ceres. Although the identification as M. perplexus is likely, we have not seen the material and therefore cannot confirm this record. Newman & Johnson (2021) noted that Erica junonia var. junonia appears to have a highly specific relationship with M. perplexus . This was the only fly species they observed on flowers of this variety (see Fig. 11.1 ). It was also seen visiting E. junonia var. junonia , Gladiolus cylindraceus and Pelargonium alpinum at Hansiesberg. The second author (JFC) observed M. perplexus visiting Pelargonium alpinum on the Gydoberg near Ceres.

Figures

FIGURE 6 (6.1–6.4). Moegistorhynchus perplexus Bequaert, 1935 (female holotype). 1. Whole body, lateral view. 2. Label data. 3–4. Head. 3. Frontal view. 4. Oblique lateral view, showing detail of antennae.

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 10 (10.1–10.4). Male terminalia: dorsal (left) and ventral (right) views. 1–2. Moegistorhynchus perplexus. 3–4. Moegistorhynchus turneri.

FIGURE 11 (11.1–11.4). Photographs of live adult Moegistorhynchus. 1. M. perplexus taking up nectar from Erica junonia var. junonia; note the large amount of pollen on the proboscis (photo credit: Steve Johnson). 2. M. turneri from Waboomsberg taking up nectar from Erica irrorata Guthrie & Bolus (photo credit: Ross Turner). 3. M. turneri from the Matroosberg feeding on Erica daphniflora Salisb var. daphniflora (photo credit: Magriet Brink). 4. Female M. brevirostris apparently ovipositing on a rocky substrate (photo credit: Lily Rose).

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).