A review of Southern African Choerades Walker , 1851 with the description of a new species ( Diptera , Asilidae , Laphriinae )

Southern African Choerades Walker, 1851 are reviewed. Six species are recognised (C. analogos sp. n. described from South Africa: KwaZulu-Natal, C. bella (Loew, 1858), C. flavipes (Wiedemann, 1821), C. multipunctata (Oldroyd, 1974), C. nigrapex (Bigot, 1878), C. nigrescens (Ricardo, 1925)) and a key for their separation is provided. Distributional information demonstrates that species are found primarily in moderate to higher rainfall regions. The little that is known of their biology is discussed. Species are usually associated with indigenous forest habitats where larval development takes place in decomposing wood.


Introduction
Choerades Walker, 1851 is a fairly well represented genus in the afrotropics with some 25 recorded species (Londt 2015, Londt andDikow 2017).While a modern taxonomic revision of all Afrotropical representatives is still awaited, the Southern African representatives have been reasonably well documented and a brief taxonomic history of these taxa follows: Wiedemann (1821: 238-239) 8) assigning his aurigena Walker, 1851 from 'Java or Sumatra' to the genus.Note: C. aurigena was subsequently found to be a synonym of an Oriental species, Laphria vulcanus Wiedemann, 1828(Oldroyd 1975).Walker (1857) -Described Laphria fortipes from 'Port Natal' [= Durban, KwaZulu-Natal, South Africa].Note: The type, originally in the W.W. Saunders collection, was presumably incorporated into the BMNH collection.Loew (1858) -Described the female of 'Laphr.bella' on material from 'Caffraria (Wahlb.)'.In this case Caffraria included parts of present day KwaZulu-Natal Province of South Africa (see Usher 1972).Bigot (1878: 229) -Described Dasythrix nigrapex, querying its placement in the genus.
At the commencement of this project there were, therefore, seven recognised species of Choerades recorded from Southern Africa (aureopilosa, bella, flavipes, fortipes, metalli, multipunctata, nigrescens Fig. 1).Two of these, fortipes and metalli, both described by Walker, have not been studied since the publication of their descriptions and it is now believed that the type material, which one suspects should be housed in the Natural History Museum in London (BMNH), is probably lost.Walker's rather superficial description of Laphria metalli, probably based on a single female, might suggest Choerades, but this almost entirely black species is probably too large, with a body length of '12 lines' (c.2.5 cm) and a wingspan of '23 lines' (c.4.9 cm), to be confused with any of the species (nigrapex, flavipes, multipunctata) now known to inhabit the area formerly known as the 'Cape' (i.e.South Africa's Western Cape Province and possibly parts of the Eastern and Northern Cape Provinces).Until such time as the type material can be traced and studied it is considered best to consign this species to the list of 'Unplaced species' generated by Oldroyd (1980: 373) and updated by Londt andDikow (2017: 1113).Walker's description of Laphria fortipes Walker, 1857 from 'Port Natal' (Durban) is perhaps better in that all aspects of the description agree well with the male of Laxenecera albicincta (Loew, 1852), a widespread species also originally described in Laphria, on material from Mozambique.While it is tempting to contemplate placing fortipes in the synonymy of Laxenecera albicincta, Walker was clearly familiar with Laxenecera as he published descriptions of species in this genus in 1855.Again, the conservative approach would be to merely list fortipes as an 'Unplaced species' until such time as the type material becomes available for study.Clearly, in the absence of Walker's types it is not possible to include his two species, fortipes and metalli, in this study.

Materials and methods
Terminology follows mainly that proposed by McAlpine (1981), Wootton and Ennos (1989, wing venation), Stuckenberg (1999, antennae), Cumming and Wood (2017) as well as that used by the authors in more recent publications.Specimens available for study are housed in the following institutions (names of assisting curators in brackets): Material listed for each species is arranged according to geographical coordinates within countries (alphabetically).Material previously listed by Londt (1977) is relisted followed by an asterisk (*).Label data relating to sampling events and type designations are usually cited as appearing on labels, lines of data being separated by a slash (/), data appearing on the reverse side of labels is indicated by the symbol ~.Unique specimen identifiers, when available, are also provided.To save space, labels relating to previous identifications are excluded unless they cite names not currently accepted as valid.While more recently collected material is frequently provided with detailed information relating to locality and habitat, it has been necessary to attempt to establish reasonably accurate geographic coordinates for older or relatively poorly documented specimens in order to gain a better understanding of distribution.Google Earth and the Internet have been used to accomplish this.Relevant information not appearing on labels is provided in square brackets.Wings were detached and placed in alcohol between two glass slides for photography before being dried and reattached to their respective specimens.Terminalia were excised and macerated in hot Potassium Hydroxide (KOH), drawn with the aid of a drawing tube before being stored in micro vials attached to specimen pins.Wing length was measured from the humeral crossvein to tip and the breadth was determined at the maximum extent.Whole habitus photographs of pinned specimens were taken in two labs with different equipment.A GIGAmacro Magnify 2 system, a Canon EOS D5 full-frame DSLR, a Canon MP-E 65 mm f2.8 macro-lens and illuminated by a twin-flash was used for the specimens photographed at the USNM.Here, individual RAW format images were stacked using HeliconFocus Pro (version 6.7.1) utilising Method C (pyramid) and exported in Adobe DNG-format.The scale was added with HeliconFocus Pro.Other photographs of specimens at the NMSA were taken with a stereo microscope and attached digital camera.No scale was added to these photographs.Some of the photographs have been deposited in Morphbank: Biological Imaging.These images will be automatically harvested by the Encyclopedia of Life (EOL) and are available under the respective species page.The dichotomous, interactive key has been built with Lucid Phoenix and can be accessed on Lucidcentral and the junior author's research web-site.The occurrence of all species is illustrated in distribution maps plotted with SimpleMappr with all of those localities for which co-ordinates are available.Type localities are plotted with a square symbol while all other specimens are plotted with a circular symbol.The distribution map includes Biodiversity Hotspots sensu Conservation International (Mittermeier et al. 1998, Myers et al. 2000, Mittermeier et al. 2005).All taxon names have been registered in ZooBank (Pyle and Michel 2008).

Data resources
Morphbank: image collection ID -861932.Lucid Phoenix: illustrated, dichotomous identification key -http://keys.lucidcentral.org/keys/phoenix/choerades/ SimpleMappr: distribution maps -10187 as in Fig. 1 (Google Earth KML format 10187), 10189 as in Fig. 27 (KML format 10189), 10190 as in Fig. 28 (KML format 10190) Diagnosis.The following diagnosis is compiled from key characters used by Londt & Dikow (2017) and other characters common to all Afrotropical species.Usually shiny black flies, ranging from 1-2 cm in length and slightly dorsoventrally flattened, with the following combination of characters.Head: Antennal postpedicel at most twice as long as scape and pedicel combined; postpedicel with terminal pit enclosing a seta-like sensory element; facial protuberance well-developed in dorsal and ventral regions (depressed centrally); face with shiny scale-like setae laterally, adjacent to eye margin ; proboscis long, straight, narrow and laterally compressed (knife-like, Figs 16-17); maxillary palpus cylindrical, 2-segmented.
Legs: Usually predominantly black, but femora and tibiae may be partly or extensively yellow (Figs 15,19); prothoracic tibia without spine-like processes; metathoracic femur not obviously expanded medio-distally, with regular ventro-distal macrosetae (i.e.not inserted on tubercles); claws and pulvilli present and well-developed.
Abdomen: Tergite 2 wider than long; sternite 1 confined beneath tergite 1; ovipositor short and not markedly tubular.Taxonomy.Since the reallocation of Laphria serpentina Bezzi, 1908 to Andrenosoma by Tomasovic (2007) the published records of this species by Oldroyd (1974) and Londt (1977) clearly require re-evaluation.These specimens (listed below) clearly belong to Choerades and so were incorrectly assigned to serpentina at those times.Until such times as a complete review of the Afrotropical fauna is undertaken it is appropriate to provide this fairly distinctive Southern African species with a name.
Description.Based on all material studied.Entire holotype as illustrated (Fig. 2).Head: Black, silver pubescent, black and white setose.Antenna black, scape and pedicel black setose (a few white setae may be present).Face black, silver pubescent.Mystax predominantly black (a few white setae may be present) with macrosetae confined to elevated parts of facial protuberance.Lateral parts of face with groups of glistening silvery scale-like setae.Frons and vertex silver pubescent, largely asetose except for black setae adjacent to eye margins.Ocellar tubercle prominent, weakly setose except for a pair of strong ocellar macrosetae.Occiput silver pubescent, strongly setose (black dorsally, white ventrally).Palps black and white setose.
Terminalia: ♂ terminalia as in Fig. 13 (previously published as fig. 5 by Londt (1977) for C. serpentina).Hypopygium rotated through 180°.Gonocoxites abut ventrally, apparently partly fused medially, hypandrium apparently absent.Note: In contrast to other Southern African species analogos sp.n. possesses an exceptionally long aedeagus that projects far beyond the level attained by the gonostyli.Like nigrescens and multipunctata there is a single pair of exceptionally long, closely associated macrosetae at about midlength on the ventral face of the gonocoxite.
Type material.Holotype: SOUTH AFRICA: Note: Bezzi (1908) based his description of serpentina on two specimens.The male 'Type' was given Lectotype status by Tomasovic (2007) when he transferred the species to Andrenosoma.The female 'Paratypus', listed above, was not mentioned by Tomasovic (2007).This specimen, which accompanies the male, is clearly not conspecific and definitely belongs to Choerades.While it appears to represent the species here called analogos sp.n. it falls outside the area covered by this study and could therefore represent another species.A complete review of the Afrotropical fauna is necessary to provide taxonomic stability.Additional material not studied.Oldroyd (1974: 102)  Distribution, phenology and biology.A poorly-collected species with an apparently wide Southern African distribution (Fig. 27, see also Fig. 1 for DR Congo and Kenya records) involving South Africa (KwaZulu-Natal) and Namibia.Available data suggest adults are active during late summer (Table 1).The species is apparently associated with forested habitats.C. analogos sp.n. is distributed within the Maputaland-Pondoland-Albany biodiversity hotspot, but also occurs outside of it.A single prey record is known (Hemiptera: Flatidae).

Redescription.
Based on all material studied.Entire male and female specimens are shown in Figs 14-19.
Terminalia: ♂ terminalia as in Fig. 10   setae confined to elevated parts of facial protuberance.Lateral parts of face with groups of glistening silvery scale-like setae.Frons and vertex dull gold pubescent, largely asetose except for black setae adjacent to eye margins.Ocellar tubercle prominent, weakly setose except for two pairs of strong ocellar macrosetae.Occiput silver pubescent, strongly setose (black dorsally, white ventrally).Palps black and white setose.
Wings (Fig. 5): Length (humeral crossvein to tip) x breadth (maximum): ♂ 8.4 × 2.8 -10.8 × 4.2 mm (mean -5 specimens -9.6 × 3.4 mm), ♀ 8.9 × 3. Distribution, phenology and biology.A relatively well-collected South African endemic with a distribution centered in the Western Cape Province (Fig. 27) but extending into the Northern and Eastern Cape provinces.Data indicate that adults have a relatively long period of activity ranging from September through to March (there are single records for July and May), with a peak in December (Table 1).The species apparently inhabits a wide range of habitats from indigenous forest to more open areas of macchia where adults are usually found sunning themselves on vegetation.C. flavipes is endemic to three biodiversity hotspots sensu Conservation International.It occurs primarily within the Cape Floristic Region biodiversity hotspot, but is also distributed within the Maputaland-Pondoland-Albany and Succulent Karoo biodiversity hotspots.Little is known of their biology, but one specimen, collected at Kirstenbosch National Botanical Garden, Cape Town (SANC-DIPT-02272) is pinned together with its pupal exuvium and labelled as having been collected from an indigenous Silver Tree (Proteaceae: Leucodendron argenteum) where the larva had presumably been feeding.(Oldroyd, 1974) http://zoobank.org/216E1006-C478-47F7-8196-944507E4B71EFigs 6, 21-24, 28 Laphria multipunctata Oldroyd, 1974: 102. Choerades multipunctata: Londt 1977: 47.Redescription.Based on material examined and photos of BMNH specimens.The entire lectotype male specimen is shown in Figs 21-22.

Choerades multipunctata
Head: Black, weakly silver pubescent, black and white (few) setose.Antenna black, scape and pedicel black setose.Face black, weakly silver pubescent laterally, depressed centrally.Mystax black (a few fine white setae may be present along epistomal margin), macrosetae confined to elevated parts of facial protuberance.Lateral parts of face with small groups of glistening silvery scale-like setae.Frons and vertex shiny apubescent, largely asetose except for black setae adjacent to eye margins.Ocellar tubercle prominent, weakly setose except for a pair of strong black ocellar macrosetae.Occiput largely apubescent except for narrow strips along eye margins, black setose (few small white setae ventrally).Palps black and white setose.
Terminalia: ♂ terminalia as in Figs 23, 24.Rotated through 180°.Epandrium weakly bilobed distally bearing c. 7 long, well-developed, laterally situated macrosetae on both sides.Proctiger extending far beyond epandrium, with elongate ventral lamellae.Gonocoxites well-developed, distally bifurcate, ventral lobe bearing short, closely associated and probably fused macrosetae (typical of the genus) distally.Dorsal lobes dorsoventrally flattened and downturned distally.Gonocoxites with a pair of exceptionally long, closely associated, twisted macrosetae (each appearing oval in crosssection).Gonostyli project well beyond dorsal lobes of gonocoxites and also possess dorsoventrally flattened and downturned distal ends.Hypandrium apparently entirely wanting.Aedeagus elongate with trifurcate tip.Material not examined.Photos supplied by the BMNH confirm the identifications of the following specimens and provide the following detailed information.As Oldroyd (1974) failed to designate a holotype, all the material handled by him should be considered syntypes (and all but one were labelled as such by Chainey in 1984).For taxonomic stability we hereby designate a BMNH male collected at Matjiesfontein between 6-15.x.1928 as Lectotype (NHMUK012804995).Oldroyd's other specimens are considered Paralectotypes as indicated below (and above), except for the male from Worcester as this locality was not listed by Oldroyd (1974) Distribution, phenology and biology.A relatively poorly-collected South African endemic known from only five localities in the Western Cape Province (Fig. 28).Material has been collected in October and November.Nothing is known of the preferred habitat, but the localities suggest vegetated valleys in areas dominated by Cape macchia vegetation.C. multipunctata is endemic to two biodiversity hotspots sensu Conservation International.It occurs primarily within the Cape Floristic Region biodiversity hotspot, but is also distributed within the Succulent Karoo biodiversity hotspot.Nothing is known of the biology.
Notes.With the discovery that Bigot's (1878) Dasythrix nigrapex, subsequently synonymized with C. flavipes (Wiedemann, 1821) by Oldroyd (1974: 102), is actually a valid species identical to aureopilosa, it becomes necessary to stabilize the taxonomy by formally recognizing nigrapex as belonging to Choerades and synonymizing aureopilosa and variabilis with it.This action is regrettable as aureopilosa has been one of the more commonly referred to species in the Southern African fauna.Although the authors have only seen good photographs of the unique holotype (Fig. 25), housed in the Oxford University's collection (OXUM), Zoë Simmons has been able to confirm that it conforms well with the following redescription based on material available to the authors.
Redescription.Based on all material studied.Head: Black, silver and gold pubescent, black and white setose.Antenna black, scape and pedicel black setose.Face black, gold pubescent.Mystax predominantly black (a few pale yellow setae may be present 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 fine gold pubescent, largely asetose except for black setae adjacent to eye margins.Ocellar tubercle prominent, weakly setose except for a pair of strong black ocellar macrosetae.Occiput silver pubescent, strongly setose (black dorsally, white ventrally).Palps black and white setose.
Thorax: Black, silver pubescent, black, white and pale yellow setose.Cervical sclerite entirely black setose.Mesonotum apubescent, predominantly pale yellow (some ♂) or black (♀ and some ♂) setose.Lateral macrosetae predominantly black (a few yellow 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 scalelike 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.

Discussion
Although Choerades is a fairly large and widely distributed Afrotropical genus in need of modern taxonomic revision, the Southern African species are reasonably well represented in collections.There are only six species presently recognized from the subregion, and available material allows for the generation of reasonably good distribution maps.Only two species (analogos sp.n. and nigrescens) have so far been recorded beyond the sub-region, but far more information about this species is required.Three of the six species (bella, flavipes, multipunctata) are currently endemic to South Africa, while the others have also been recorded from neighbouring countries.Very little biological data exist.While most Afrotropical species are usually associated with indigenous forests, where adults are usually found perching on leaves in sunny patches, it appears that two of the South African species (multipunctata, nigrapex) inhabit somewhat drier environments.Interestingly, these two species are, like the other Southern African species, summer active even though they inhabit areas that experience winter rainfall.An adult of C. flavipes, pinned with its pupal exuvium together with a note reporting that it was removed from the wood of a Silver Tree (Proteaceae, Leucodendron argenteum) is evidence that the genus, like many other genera within the Laphriinae, utilizes rotting wood as a larval environment.All six species occur within biodiversity hotspots sensu Conservation International and two are endemic to these hotspots, i.e., C. flavipes to Cape Floristic Region, Maputaland-Pondoland-Albany, and Succulent Karoo (Fig. 27) and C. multipunctata to Cape Floristic Region and Succulent Karoo (Fig. 28).Choerades nigrapex is almost endemic to biodiversity hotspots as it occurs in the Maputaland-Pondoland-Albany, Cape Floristic Region, and Eastern Afromontane biodiversity hotspot, but has been collected at a single locality outside of the latter hotspot.Only four prey records are available which feature four different insect orders -Hemiptera (Flatidae), Diptera (Bibionidae), Hymenoptera (Formicidae) and Coleoptera (unidentified family).It appears, therefore, that species of Choerades are generalists when it comes to adult diet.

Figure 1 .
Figure 1.Map of southern parts of the Afrotropical Region with elevational relief, Biodiversity Hotspots (sensu Conservation International in grey), and distribution of Southern African Choerades specimens (SimpleMappr 10187, map data also available in Google Earth KML format 10187).

Figure 28 .
Figure 28.Map of Southern Africa with elevational relief, Biodiversity Hotspots (sensu Conservation International), and distribution of Choerades multipunctata and C. nigrapex (SimpleMappr 10190, map data also available in Google Earth KML format 10190).

Table 1 .
Phenology of Southern African Choerades species (Abbreviations of months start at July, numbers relate to records for each month).All available data included.