Moegistorhynchus brevirostris ( Wiedemann, 1821 )

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 : 9-13

Moegistorhynchus brevirostris ( Wiedemann, 1821)

( Figs 3.1–3.9 , 9.3–9.4 , 11.4 , 12 )

Nemestrina brevirostris Wiedemann, 1821: 156 .

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

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

Type material ( lectotype and paralectotype in ZMUC): South Africa: Western Cape: LECTOTYPE: ♂: “ ♂ ”; “Mus. / Westerm.”; “TYPE” [red card]; “ N. brevirostris / Wied. / Cape Good Hope / Octb. 1817” [handwritten in Wiedemann’s hand]. PARALECTOTYPE: ♀: “ ♀ ”; “Mus. / Westerm.”; “TYPE” [red card]. The lectotype and paralectotype are in excellent condition, although the tarsi are missing from two right legs (mid and hind) in both specimens. Both are appropriately labelled.

Notes on lectotype / paralectotype designation. We located the male and female syntypes of Nemestrina brevirostris Wiedemann, 1821 , in ZMUC (male and female are referred to in the original description). The lectotype is appropriately labelled in Wiedemann’s hand and both lectotype and paralectotype are appropriately labelled “Mus. Westerman”. The lectotype is also labelled “ Cape Good Hope ” as noted (in Latin) in the original description. The lectotype and paralectotype had previously been labelled as “ TYPE ” on red card. The lectotype label is as follows: “ LECTOTYTPE MALE [in bold] / Nemestrina brevirostris / Wiedemann, 1821 / Designated by D.A. Barraclough & / J.F. Colville ” [on red card]. The paralectotype label is identical, except for the wording “ PARALECTOTYPE FEMALE”.

Other material: Western Cape: 1♀, Atlantis, Silverstroomstrand turnoff, 33.56528 18.38460, 20 October 2015 ( NMSA) ; 1♂ 2♀, Ganzekraal , S33°35’ E18°20’, 7 October 1995 ( NMSA) ; 1♂ 1♀, 6 km E. Silverstroomstrand, S33°35’ 47.6” E018°23’15.5”, 15 October 2002, B.C. Anderson, in Strandveld, 1 km E. of R27, visiting flowers, 10h00 ( SAMC) ; 1♀, Strandfontein, Cape Flats, 5 October 2014, Andrew Morton ( SAMC) ; 1♀, Strandfontein, False Bay , 1 November 1960 ( SAMC) . Northern Cape: 1♂, Kamieskroon Grootvlei Pass [577 m], 30.21721 17.769171, September 2015, Allan Ellis ( NMSA) ; 1♀, Leliefontein , 15 September 2008, Timo van der Niet ( NMSA) ; 1♂, Lelie[fontein], 10 October, S. erectum (no other data) ( SAMC) ; 1♂, 5 km from Leliefontein on road to Groenkloof, 2 October 1995, F.W., S.K. & R.W. Gess, on blue flowers of Anchusa capensis ( AMGS) .

Diagnosis. Postpedicel mostly dark, but with striking paler basal annulation; style with two basal segments. Proboscis short, noticeably shorter than 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 without dense clustering of dark pile on posterolateral extremities.

Redescription (both sexes). Body length 14.37–18.02 mm ( Fig. 3.1 ); wing length 16.23–18.74 mm; proboscis length 12.33–20.51 mm. Head ( Figs 3.3–3.4 ): colouring yellow-brown to dark brown to black with scape and pedicel mostly yellow or yellow-brown. Postpedicel mostly dark brown to black but with striking yellow to orange basal annulation on both surfaces. Male with anterior ocellus and posterior ocelli separated by deep transverse groove; anterior and posterior ocelli all about equidistant apart and therefore forming the three corners of an equilateral triangle. Frons with elongate yellow pile (sometimes partly black posteriorly), pile over much of surface except sometimes anteromedially. Style of flagellum with two short basal segments, with second segment sometimes slightly longer than first segment or vice versa. Proboscis notably short, length two-thirds body length ranging up to slightly less than body length. Thorax ( Figs 3.5–3.6 ): scutum pale (occasionally), 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 dark orange in medial area at two-thirds distance between anterior margin and scuto-scutellar suture, this orange colouring extending 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 this position there is sometimes an inverted V-shaped extension of dark pruinescence. 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 may be mostly yellow; short but profuse but largely sparse to absent on posterior half (although present here 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, but sometimes a paler yellow-brown. Fore femur with relatively elongate backwardly directed pale pile, this sometimes reaching up to one-third femur length. Mid and hind femora with sparse ventral pile (similarly coloured) along basal two-fifths to three-quarters of mid femur and along basal half to two-thirds of hind femur. Wing ( Fig. 3.7 ): relatively broad, length at most 3.0 x maximum width. Infuscation a relatively dark brown. Patterning irregular and distributed over much of wing as in figure, although hyaline areas dominate apically and posteriorly; hyaline areas strikingly distinguished and clearly separate from brown colouring. CuP with one incomplete or complete crossvein (sometimes two complete crossveins in one wing only); if complete to posterior margin then obvious appendix sometimes present. Abdomen ( Figs 3.8–3.9 ): relatively broad and obviously broader than width of thorax, sometimes broader in female. Ground colour mostly dark brown to black and sometimes with hints of orange; sometimes partly yellow on several sternites. T1 entirely dark brown to black with obvious silver pruinescence along anterior margin, except at midline or medially and (postero)laterally; pile dense and short, mostly yellow or white but sometimes a few black hairs. T2 dark (brown) medially and submedially, with silver pruinescence obvious (antero)laterally; pile short, sometimes over entire surface. T3 largely dark brown to black but sometimes orange-tinged or obviously orange laterally and posteriorly, and with striking paired silver pruinescence/markings (irregularly quadrate) on anterior two-thirds, these markings extend partly or entirely to lateral margins, meaning that the silver pruinescence can be strikingly confluent and continuous; pile sparse, pale and relatively short to moderately long on anterior oneto two-thirds, with fringe of short serial black pile at posterolateral extremities (this sometimes very short in female). T4 similarly coloured and patterned; pile typically present anteriorly (sometimes virtually absent in female) where very sparse, this pale in colour, longest hairs reaching half length of T4 margin or slightly longer and posterolateral extremities with serial dark pile. T5 usually even more extensively silver pruinescent with large brown area medially (which extends to posterior margin or towards it) and submedially (this area very small); pile sparse and pale or absent; posterolateral extremities with serial dark pile. T6 similarly coloured and patterned but median dark area sometimes with lateral extensions only; pile as on T5 but along entire margins and without serial dark pile on posterolateral extremities. Sternites yellow-brown to dark brown to black; pile notably elongate and white on S3 and sometimes S4. Male postabdomen ( Figs 9.3–9.4 ): epandrium very slender in dorsal view, maximum width much broader than length, with obvious apical notch above cerci, apicolateral extremities broadly rounded to flattened in lateral view. Gonostylus with no vestiture along inner medial margin or this vestiture very inconspicuous, presenting as two lobes: a slender but well developed inner lobe and a very short and apically rounded outer lobe, inner lobe with apical region strongly narrowed and sometimes slightly outwardly curved. Inner gonocoxal process straight and very slender, sharply pointed to narrowly rounded apically, apical region without marginal teeth. Phallus apex about coincident with or falling just short of gonostylus apices in ventral view, without obvious marginal dentition (minute dentition sometimes visible).

Relationships and distribution. Moegistorhynchus brevirostris is most similar to M. longirostris . It is a more slender and less robust species with a very much shorter proboscis. As with M. longirostris , it is a lowland species and is widespread. However, it is not as frequently encountered in the field and is distributed between Strandfontein east of Muizenberg on False Bay in the Western Cape in the extreme south through to Kamieskroon in the Northern Cape in the north ( Fig. 12 ). Vegetation type: Atlantis Sand Fynbos (FFd4); Cape Flats Dune Strandveld (FS6); Namaqualand Granite Renosterveld (FRg1); Langebaan Dune Strandveld (FS5); and Namaqualand Klipkoppe Shrubland (SKn1).

Discussion. Although fairly variable in colouring across its range, it is unlikely that M. brevirostris represents a species complex. We have dissected males from the south and north of the geographical range and there is no significant variation in the form of the male terminalia.

The species seems to be of little significance in pollination biology and there is little reference to it in the literature. It has been recorded as visiting the blue flowers of Anchusa capensis Thunb. in the Northern Cape (see material examined).

An iNaturalist observation shows a single female of M. brevirostris apparently ovipositing on a rocky substrate just north of the Wolfgat Nature Reserve and south of Tafelsig in the Khayelitsha area of the Cape Town Metro (https://www.inaturalist.org/observations/137461195) ( Fig. 11.4 ). This is the only time we have seen an image of a Moegistorhynchus ovipositing in the field and this offers clues about the natural history of the genus.

We have previously seen one male in NHMUK from Raapenburg (Little Mowbray, Cape Town ), which was collected by R. E. Turner from 1 to 14 October 1920. However, this specimen is not included in the redescription .

Figures

FIGURE 3 (3.1–3.4). Moegistorhynchus brevirostris (Wiedemann, 1821) (lectotype male). 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 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).