Choerades nigrescens (Ricardo, 1925)

Londt, Jason G. H. & Dikow, Torsten, 2019, A review of Southern African Choerades Walker, 1851 with the description of a new species (Diptera, Asilidae, Laphriinae), African Invertebrates 60 (1), pp. 31-65 : 53-59

Choerades nigrescens (Ricardo, 1925) Figs 8, 12, 26, 27

Laphria nigrescens Ricardo, 1925: 279; Bromley 1935: 405 (key); Oldroyd 1970: 227 (key).

Choerades nigrescens : Londt 1977: 47 (fig. 4 ♂ terminalia).

Notes.

Ricardo (1925: 279-280) described the species on 'Type (male) and four other males. Type (female) and four other females. All from Mt. Mlanje, Nyasaland (S.A. Neave).' In doing so she did not designate a holotype so all her listed specimens must be considered syntypes. We hereby designate one of the males as Lectotype, and the other specimens Paralectotypes.

Redescription.

Based on NMSA material. An entire male specimen is shown in Fig. 26.

Head: Black, silver pubescent, black and white setose. Antenna black, scape and pedicel black setose. Face black, dull silver pubescent, depressed centrally. Mystax mainly black, but white dorsally and ventrally, with macrosetae confined to elevated parts of facial protuberance. Lateral parts of face with groups of glistening silvery scale-like setae. Frons and vertex dull silver pubescent, weakly setose except for moderately developed black setae adjacent to eye margins. Ocellar tubercle prominent, weakly setose except for a pair of strong black ocellar macrosetae. Occiput weakly silver pubescent, black (dorsally) and white (ventrally) setose. Palps black and white setose.

Thorax: Black, silver pubescent, black and white setose. Cervical sclerite black and white (♀) or entirely white (♂) setose. Mesonotum apubescent except for weakly silver pubescent laterally margins and postpronotal lobes, predominantly black setose. Lateral macrosetae black (1 notopleurals, 2 supra-alars, 3 postalars). Scutellum black, shiny apubescent, fine white setose, c. 8 slender apical scutellar macrosetae (mostly white but some may be black). Pleura silver pubescent, mostly fine white setose (a few stouter black macrosetae present). 1 black anepisternal macroseta. Katatergal setae well-developed, mostly white (ventrally) but a few black (dorsally). Anatergites weakly silver pubescent, weakly setose laterally.

Legs: Almost entirely black except for proximal half of metathoracic tibiae which are dull orange, coxae silver pubescent, other segments apubescent. Trochanters white setose, femora and tibiae mostly white setose, but with some black setae.

Wings (Fig. 8): Length (humeral crossvein to tip) x breadth (maximum): ♂ (1) 7.7 × 2.7 mm, ♀ (6) 6.6 × 2.3mm - 9.2 × 3.2 mm (mean 8.2 × 3.0mm). Veins dark red-brown to black, membrane transparent, distal two-thirds microtrichose, basal cells almost devoid of microtrichia except distally.

Abdomen: Black, sternites and lateral margins of tergites weakly silver pubescent, mostly white setose (tergites medially with minute black setae). T1 laterally with fine white discal setae and 2-4 black macrosetae (♀).

Terminalia: ♂ terminalia as in Fig. 12 (previously published as fig. 4 by Londt (1977)). Hypopygium rotated through 180°. Gonocoxites abut ventrally, hypandrium apparently absent.

Material examined.

MOZAMBIQUE: 1♀ 'Marromeu [c. 18°16'06"S, 35°53'18"E 10m] Lower / Zambezi River / Port East Africa’, 'Salone Forest / Dec. 1959 / Stuckenberg’, NMSA-DIP-08882 (NMSA)*; 1♀ 'xi 1935 / H W Bell Marley’, 'Muputa M [Maputo Mozambique c. 25°58'09"S, 32°34'24"E 35m]', SAMC-DIP- A007963 (SAMC); SOUTH AFRICA: 1♂ 'South Africa: Natal / Ndumu Game Reserve / Rest Camp [c. 26°54'35"S, 32°18'47"E 95m] 2632Cd 95m / 23-9:xi.1977 Malaise / Brothers & J. Guillarmod’, NMSA-DIP-08880 (NMSA); 2♀, 'Manguzi [c. 27°00'00"S, 32°45'28"E 30m] River / Nr. Maputa, Zululand / Nov.-Dec. 1945 / H.W. Bell Marley’, DMSA-DIP1009-10 (DMSA)*; 3♀ 'South Africa, Natal Prov / 10mi. N. Josini [c. 27°16'28"S, 32°04'47"E 165m] (2732Ac) / Nov. 28. 1971; ME & BJ Irwin / dry forest; 800ft. el.', NMSA-DIP-08872 [1♀] NMSA-DIP-81822-23 (NMSA)*; 1♀ 'Umziki Pan [c. 28°02'00"S, 32°19'00"E 80m] / W Shores St. Lucia / Mosaic coastal / bush. 31.1.93', NMSA-DIP-08881 (NMSA); 1♀ 'Trollips [?] / on window frame / 5pm. 26.12.78', NMSA-DIP-08884 (NMSA).

Note: We have also seen the following specimen from Zambia which suggests that the species is fairly widely distributed in East Africa and possibly Central Africa and has its southern limits in northern KwaZulu-Natal.

Extralimital material examined.

The following specimen, identified as nigrescens , extends the distribution into Central Africa: ZAMBIA: 1♂ 'Malaise traps / Central Zambezian / Miombo Woodlands’, 'Zambia: Mumbwa Dist. / Kafue National Park / Muyukuyuku camp area at: / 14°54.898'S, 26°03.820'E / 3-5.xii.2012. 1081m / A.H. & M.K. Kirk-Spriggs’, BMSA(D)48832.

Material not examined.

The senior author has seen photographs of the following specimens which are included such that distributional information is more complete.

Lectotype: MALAWI: 1♂ 'Type / H.T.' [circular, red border], 'Pres. by / Imp. Bur. Ent. / Brit. Mus. / 1923-58', 'Nyasaland / Mt. Mlanje [c. 15°56'55"S, 35°35'26"E 2940 m] / 31.xii.1912 / S.A. Neave’, 'Syntype [circular, blue edge] / Syntype / Laphria / nigrescens Ricardo / det. J.E. Chainey, 1984', ‘NHMUK012810461’ (BMNH).

Paralectotypes: MALAWI: 1♀ similarly labelled as lectotype ‘NHMUK012810462’ (BMNH); 2♀ 2♂ 'Pres. by / Imp. Bur. Ent. / Brit. Mus. / 1923-58', 'Nyasaland / Mt. Mlanje / 20.xi.1912 / S.A. Neave’, 'Syntype [circular, blue edge] / Syntype / Laphria / nigrescens Ricardo / det. J.E, Chainey, 1984', 'NHMUK012810463, NHMUK012810465, NHMUK012810467 & NHMUK012810469' (BMNH); 1♀ 'Pres. by / Imp. Bur. Ent. / Brit. Mus. / 1923-58', 'Nyasaland / Mt. Mlanje / 27.xii.1912 / S.A. Neave’, 'Syntype [circular, blue edge] / Syntype / Laphria / nigrescens Ricardo / det. J.E, Chainey, 1984', ‘NHMUK012810464’ (BMNH); 1♀ 'Pres. by / Imp. Bur. Ent. / Brit. Mus. / 1923-58', 'Nyasaland / Mt. Mlanje / 22.ii.1913 / S.A. Neave’, 'Syntype [circular, blue edge] / Syntype / Laphria / nigrescens Ricardo / det. J.E, Chainey, 1984', ‘NHMUK012810466’ (BMNH); 1♀ 'Pres. by / Imp. Bur. Ent. / Brit. Mus. / 1923-58', 'Nyasaland / Mt. Mlanje / 15.i.1913 / S.A. Neave’, 'Syntype [circular, blue edge] / Syntype / Laphria / nigrescens Ricardo / det. J.E, Chainey, 1984', ‘NHMUK012810471’ (BMNH).

Other specimens.

BOTSWANA: 1♂ 'nr. Nata [c. 20°12'38"S, 26°10'38"E 915m] / Bechuanaland [= Botswana] / xii.1954', 'Laphria / nigrescens Ricardo / det. J.E. Chainey, 1943', ‘NHMUK012810861’ (BMNH). MALAWI: 1♂ '24.iii.13 / S.A.N.', 'Mlanje / Nyasaland, 1913 / S.A. Neave’, 'Pres. by / Imp. Bur. Ent. / Brit. Mus. / 1923-340', ‘NHMUK012810473’ (BMNH); 1♂ 'Nyasaland / Mlanje / J.B. Davey’, 'Pres. by / Imp. Bur. Ent. / Brit. Mus. / 1923-340', ‘NHMUK012810474’ (BMNH); 1♂ 'F2 × F3 / Mlanje / Nyasaland / 14.ii.1913 / S.A. Neave’, 'Pres. by / Imp. Bur. Ent. / Brit. Mus. / 1923-340', ‘NHMUK012810475’ (BMNH); 1♀ 'F3 × F2 / Mlanje / Nyasaland / 14.ii.1913 / S.A. Neave’, 'Pres. by / Imp. Bur. Ent. / Brit. Mus. / 1923-340', ‘NHMUK012810476’ (BMNH); 1♂ 'Mlanje / Nyasaland / 12.ii.1914 / S.A. Neave’, 'Pres. by / Imp. Bur. Ent. / Brit. Mus. / 1923-340', ‘NHMUK012810477’ (BMNH). MOZAMBIQUE: 1♀ 'D x D1 / 28.xi.13', 'Portug. E. Afr. [Mozambique] / E. of Mt. Mlanje [c. 15°55'20"S, 35°50'22"E 680m] / S.A. Neave’, 'Pres. by / Imp. Bur. Ent. / Brit. Mus. / 1923-340', ‘NHMUK012810859’ (BMNH); 1♀ 'D1 × D / 28.xi.13', 'Portug. E. Afr. / E. of Mt. Mlanje / S.A. Neave’, 'Pres. by / Imp. Bur. Ent. / Brit. Mus. / 1923-340', ‘NHMUK012810860’ (BMNH).

Distribution, phenology and biology.

A relatively poorly-collected species with a Southern African distribution extending from central Mozambique to the north-eastern parts of the KwaZulu-Natal Province in South Africa (Fig. 27). Data indicate that adults have a relatively short period of activity ranging from November through to January (Table 1). The species apparently inhabits indigenous forest habitats. C. nigrescens occurs in two biodiversity hotspots sensu Conservation International (Maputaland-Pondoland-Albany and Coastal Forests of Eastern Africa), but is primarily distributed outside of them. Nothing is known of the biology.