Geographical distributions of Bembix (Hymenoptera, Crabronidae, Bembicinae) in southern Africa, with notes on biology

Geographical distributions based on available records are presented for the 37 currently recognized species of Bembix Fabricius known to occur in southern Africa. These are albata Parker, albicapilla Arnold, albofasciata Smith, anomalipes Arnold, arnoldi Arnold, atrospinosa Turner, baumanni Handlirsch, bubalus Handlirsch, cameronis Handlirsch, capensis Lepeletier, capicola Handlirsch, carinata F. Smith, cultrifera Arnold, denticauda Arnold, diversipennis F. Smith, flavicincta R. Turner, fraudulenta Arnold, fuscipennis Lepeletier, gracilens J. Parker, harenarum Arnold, karroensis Gess, liturata R. Turner, loupata R. Parker, massaica Cameron, melanopa Handlirsch, moebii Handlirsch, monedula Handlirsch, namibensis Gess, ochracea Handlirsch, olivata Dahlbom, regnata Parker, scaura Arnold, sibilans Handlirsch, triangulifera Arnold, ulula Arnold, venusta Arnold, and zinni Gess. A single specimen of Bembix compedita R. Turner has been recorded from South Africa but as the species is known principally from Malawi this requires confirmation. Some diagnostic characters are given for the hitherto undescribed female of namibensis. A range of distribution patterns are noted – narrowly endemic to widespread through the Afrotropical Region and into Egypt. Four species, albata, arnoldi, harenarum and fraudulenta appear to have strictly southern African coastal distributions. A summary of the knowledge of flower associations, nesting and prey are given for those species for which data are available.

In 1970 Friedrich Gess undertook an investigation of the Bembix specimens from the major collections of southern Africa with a view to undertaking a revision of the genus in that region. Three undescribed species and one synonymy were discovered. Some other taxonomic problems were identified but due to the inadequacy of the holdings of the relevant species and the consequent need for additional material from specific localities a revision was considered to be premature. However, Friedrich  published the three new species, namibensis, zinni and karooensis, and sank junodi Arnold into synonymy with B. ulula Arnold. In addition, in the same publication, he gave biological notes for 10 other species and a review of the nature of the prey of the genus with particular reference to the Afrotropical species. These were constituted from scattered published records (including those given in F.W. Gess 1981) which in some instances are obscure and generally overlooked, from specimen labels of the Albany Museum material and from personal observations. This represented as nearly as possible a complete compilation of the biological knowledge of Bembix and was intended to form a foundation on which to build. Subsequently, a study was made of the nesting of Bembix bubalus at Oudtshoorn in the Little Karoo .
Recently Friedrich Gess revisited the possibility of undertaking a revision of Bembix and to this end he determined a considerable number of specimens assembled since his earlier investigations. Regrettably, due to his ill health over many years and his subsequent death on 6 August 2013 the revision did not come to be. However, the wealth of material determined greatly increases the knowledge of geographical distributions of many of the species and offers previously unpublished records of floral associations, nesting and prey. Towards the end of his life Sarah Gess offered to take his unfinished manuscript and from it to produce a paper to insure that the work already done by Friedrich Gess would not be wasted. The present contribution is therefore a compilation of material examined by and determined by Friedrich together with some of his taxonomic and morphological notes. To this Sarah has added some additional records from specimens not seen by nor determined by Friedrich Gess but extracted from the Iziko South African Museum entomology collection Specify database available at www.sabif.co.za, photographs of a pair of specimens of most species, maps depicting the known geographical distributions in southern Africa, comments on the geographical the distributions of the species, and of their flower associations, nesting and prey, indicating whether or not such data are known. Clearly, although the contribution is based on the work of Friedrich Gess, it has not been checked or approved by him and therefore should errors be found he should not be held responsible for them.
As is the established practice of Friedrich Gess, the notation used for expressing geographic coordinates is as in the gazetteer of The Times Atlas of the World (Bartholomew et al. 1981). The figures before the stop are degrees, those after the stop are minutes; the stop is not a decimal point. Co-ordinates have been given in square brackets in the text for those localities for which none are given on the data labels. In instances where the locality given is imprecise the word circa is added.
For plotting the distribution maps ArcMap 10.1 GIS by ESRI was used with the co-ordinates in decimal degrees.
Acronyms for institutions in which material is housed follow Evenhuis (2013  In the lists of material examined the data are given as on the specimen labels. Any additions are given in square brackets. The collectors are given in the data string in parenthesis after collection date. Where ‚collectors' are given as an institution on the specimen data labels and not as an individual the names are as on the labels and are therefore not necessarily current institutional names and are not necessarily given in a consistent format. The acronyms in square brackets denote the institutions in which the specimens are currently housed and therefore follow current names for the institutions as given in the paragraph above.   Swakopmund [22.40S, 14.32E], vii.1931 (Bradfield), same locality 21.xii.1977 (Empey), 2 ♀♀, 4 ♂♂;same locality, 17.xii.1978 (Empey), 1 ♀ [AMGS]; Swakopmund, 15.xi.1984 (F.J. Herbst), 1 ♀; Swakopmund, 16.xi.1984 (F.J. Herbst), 3 ♀♀, 1 ♂;Swakopmund, 28.ii.1966  Geographical distribution. This species appears to have a mainly coastal distribution ( Fig. 2a). At present it is known only from Angra Fria in northern Namibia to Klipfontein near Hondeklip Bay, Namaqualand, South Africa, that is for over 12 degrees latitude and in excess of 1400 km of coastline. It is probable that its distribution may extend northwards into Angola. The only record slightly inland from the coast is that for the sandy Sperrgebiet (southern Namib Desert ) at Kaukausib Spring, Gryllenthal. Nesting. Unknown but most likely nesting in the sandy hummocks. At localities along the coast, sampled by F. W. and S. K. Gess, the species was found principally associated with the sandy hummocks formed around Brownanthus, Psilocaulon and Zygophyllum clavatum and visiting the flowers of these plants.
Prey. Three females were recorded hunting flies on Euphorbia sp. at Kaukausib Spring. Arnold described Bembix albicapilla from the unique male specimen from Insuza Forest.The specimen from Sawmills is generally melanistic when compared with the type. Most noticeable in this respect is the labrum which instead of being wholly ocreous as in the type is mostly black except for a narrow ochreous treak in the midline, somewhat expanded distally but not reaching proximal third. In addition the lemon yellow band on the first tergite is widely interrupted in the middle and the black spots on the second and third tergites are fused with the transverse basal black bands.
Geographical distribution. The species appears to have a strictly coastal distribution ( Fig. 2e). At present it is known from the Eastern Cape, from Kleinemonde to Zwartkops near Port Elizabeth and from the Western Cape at Port Beaufort. At both Boknes and Port Beaufort the species was found frequenting the first line of supralittoral dunes and visiting the flowers associated with these dunes.
Nesting. Unknown but most likely nesting in the supra-littoral dunes. At Boknes was repeatedly observed digging burrows on the seaward side of the fore-dunes.
Prey. One record only, Diptera: Muscidae (on ocean wrack on tideline).  1 ♂, 20.xii.1917, 1 ♀, 25.xii.1917    Geographical distribution. This species appears to have a southern distribution in the Succulent Karoo and southern Nama-Karoo with one outlying record from Kingwilliamstown to the east of the Nama-Karoo (Fig. 7a). The record for a syntype from the "Transvaal" seems questionable.
Nesting. Nesting in large aggregations of up to 1,000 or more nests in level friable soil, nest multicellular, sloping burrow in friable soil, the main shaft terminating in a spur, provisioning progressive. Notable for exhibiting nest sharing.
Prey. Recorded taking seven families of Diptera: Stratiomyidae, Tabanidae, Syrphidae, Bombyliidae, Muscidae, Sarcophagidae, and Tachinidae. Note. Described by Handlirsch from a male and a female from the Cape ("Cap") (Berlin Museum) and a female from "Südafrika" (P. Cameron).  examined and figured a male in the South African Museum from Tradouw Pass, Swellendam (Western Cape). The specimens examined (FWG) from Lesotho differ from those from the "Cape Province" and from the description of the species (based on Cape material) in being melanistic (i.e. in having the extent of the yellow markings reduced). Most noticeable in this respect is: scape in male entirely black (except radicle and extreme apex), in female with upper surface marked with black streaks; labrum usually with large black streaks on basal two-thirds; clypeus in male black except for a wide apical band somewhat expanded basally in midline, in female with a pair of black spots at base and sometimes a smaller pair on disc (these spots sometimes fused); yellow region on lower face between antennal sockets reduced and inner orbital bands shortened; pronotum with posterior margin black or with only a very narrow yellow band, in male with sides almost entirely black (except for small yellow area on anterior-ventral region of mesopleura), in female with yellow markings mostly present but much reduced; sterna with amount of yellow reduced; black markings on legs more extensive. Nesting. Single nest investigated -a single celled, sloping burrow in friable soil. The main shaft terminated in a spur.

Bembix capensis
Geographical distribution. The above records confirm the northern occurrence of this species in Malawi and Kenya, however, the record for Bloemfontein suggests that it is also found to the south in the Free State. As there is one record only from the south additional material is required to establish the veracity of this record.
Floral associations. Unknown. Nesting. Unknown Prey. Unknown.  Arnold (1929: 340) in his comparison with the female of speciosa Arnold (= regnata Parker) except that the mesonotal disc has well developed streaks (forming a U-shaped [yellow] mark, the lateral arms, however, not joining the basal part). Some females from Bulawayo and Umtali also show rudiments of the lateral arms of this mark. In regnata Parker this yellow mark seems to be variable in its size and development, so it is clear that it has no value as a taxonomic character to separate these two species.

Bembix cultrifera
Three specimens (determined by G. Arnold) are given in the database of SAMC, two from Victoria Falls [17.55S, 25.50E], and one from Bulawayo [20.07S,28.32E], sex not given.
Geographical distribution. Recorded from Zimbabwe, from north to south, from eastern Namibia and from Limpopo, northern South Africa (Fig. 7e).

Note.
In this species there is a marked north-south variation in colouration. Specimens examined (as listed below under Material examined) from the north, Tanzania, Zambia, Zimbabwe and northern South Africa, are characterised by the entire clypeus brownish amber, whereas in specimens examined from the south only the anterior third to half of the clypeus is brownish amber, the rest of the clypeus is black. A certain degree of ovelap of the two colour forms is noted in specimens examined from the Free State and KwaZulu-Natal. This observation is supported by the published descriptions:  in recording a female from Tabora (Tanzania) and a male from Bulawyo (Zimbabwe) stated that "The clypeus of the female before me is entirely ferruginous";  recording specimens from Zimbabwe and northern South Africa stated, "labrum and clypeus brownish amber yellow"; Handlirsch (1893) referring to specimens examined by him from "Transvaal", "Port Natal" and "Cape of Good Hope", that is from both the north and the south, noted, "Corpus nigrum, orbitus, magine apicali clipei (raro toto clipeo) et labro ferrugineo-luteis, ….". Lepeletier (1845) in his description of both sexes from the "Cap de Bonne-Espérance" stated inter alia, "Clypeus niger, margine antico ferrugineo, …". Indeed, specimens from the north are altogether less melanistic than those from the south. The pale colouring of the streak on each side of the face, the spots behind the antennal sockets, the band of spots below the ocellar region, the flagellum, the yellow spot on the posterior angles of the epinotal dorsum and the pale bands on the tergites are all greatly reduced in specimens from the south as compared with specimens from the north. Geographical distribution. Widespread in southern Africa (Fig. 9d), extending northwards to Ethiopia in the northeast and Zaire in the northwest.  Additional records extracted from database of specimens in collection of SAMC are from Plettenberg Bay and Bredasdorp, no sexes or determiners given.
Geographical distribution. The species appears to have a strictly coastal distribution (Fig. 9f). Known from Port St Johns to Brenton-on-Sea near Knysna and, if the unconfirmed record from SAMC is included, Bredasdorp.
Floral associations. Recorded from one plant family Apocynaceae (formerly Asclepiadaceae, based on pollinia carried on claws).
Nesting. Unknown, probably in the supra-littoral dunes. Prey. Recorded taking one family of Diptera: Tabanidae (one female captured with tabanid prey).

Bembix karrooensis Gess
http://species-id.net/wiki/Bembix_karrooensis Fig. 11a Bembix karrooensis Gess, 1986: 144, figs 20-24 [AMGS]. Geographical distribution. The Nama-Karoo of the Northern Cape and Namibia (Fig. 12a). Note. This species was described by Turner from Willowmore and recorded from the same locality by Arnold. In the females the sixth tergite is not always black (as stated in Arnold's key) but may be ferruginous or even yellow at the apex, in which case the general appearance ia much like that of B. capensis. Such specimens are, however, distinguishable by the pale markings on the tergite being yellowish white (not yellow), by the greater amount of yellow and lesser amount of ferruginous (if any) on the sterna, by the shape of the black mark on the clypeus, by the more gracile form of the second flagellar segment, and by the fact that the labrum at the baso-lateral angles (and sometimes laterally) is finely but distinctly pilose (almost glabrose in capensis).
The subspecies flavopicta Arnold cannot be upheld as the material examined shows that the species may vary considerably in the degree of development of the light markings. Specimens from Willowmore are usually melanistic, flavopicta has the light markings well developed, specimens from Merveville are intermediate.
Nesting. . Three nests recorded at Hilton, near Grahamstown, Eastern Cape -all single celled, sloping burrows in sloping friable soil, the main shaft ended in a spur.

Bembix moebii
Handlirsch http://species-id.net/wiki/Bembix_moebii Fig. 11e Bembex möbii Handlirsch, 1893: 775, pl. 2, fig. 2, pl. 7, fig. 1, ♂, ♀, (Syntypes, Mozambique, Delagoa Bay [Maputo], in ZMHB); Dalla Torre 1897: 508 (in catalogue of world Hymenoptera). Bembex moebii Handlirsch & Arnold, 1929: 343, figs 13, 13a, pl. 6, fig. 7 Female. (hitherto undescribed): Generally very similar to male in puncturation and setation but differing in coloration in that: streak on mesonotum flanking tegula is more pronounced; mesopleuron, metapleuron and side of propodeum are almost completely yellow; the bands margining scutellum and metanotum are wider and a V-shaped band is present on the dorsum and declivity of the propodeum. Fore tarsus unmodified; sand rake composed of nine long, stiff spines on first tarsomere, two on the second and third tarsomeres and one on the fourth; antennae unmodified (as in male with first flagellomere slightly more than twice length of second). Length: 23 mm; length of front wing13 mm; hamuli circa 33. Geographical distribution. At the time of description the provenance of the limited material was from the south-western Namib, suggesting that it might be limited to that region. The records now available indicate a much more extensive distribution in the desertic to semi-desertic western parts of Namibia (Fig. 14a)   Geographical distribution. Principally in western semi-arid to arid Namibia extending to the coast and southwards and eastwards through northern Namaqualand across the western and southeastern Nama-Karoo (Fig. 14b).   1 ♂ [AMGS].
Additional records extracted from database of specimens in collection of SAMC are six specimens from Zimbabwe and one specimen from Nyaka (no country given), no sexes or determiners given.
Geographical distribution. From north to south Zimbawe, in South Africa known from one specimen from northern coastal KwaZulu-Natal (Fig. 14d). Further records are required to establish a distribution pattern.
Widespread throughout South Africa and Lesotho and with a single record from Zimbabwe is B. albofasciata (Fig. 2c).
Species with an apparently relatively widespread eastern distribution are: B. diversipennis (Fig. 9a), from northeastern South Africa, Zimbabwe and Mozambique to Ethiopia; B. flavicincta (Fig. 9b) from Limpopo, South Africa through Zimabwe to Malawi; B. melanopa (Fig. 12d) principally from eastern South Africa and Zimbabwe to Kenya.
A species with an apparently relatively widespread principally western distribution within southern Africa and not extending northwards is B. ochracea (Fig. 14b), which appears to be a species of both the Succulent Karoo and Nama-Karoo.
Another species of the Succulent and Nama-Karoo is B. bubalus which has been recorded principally from the south of the Nama-Karoo in South Africa (Fig. 7a).
Bembix cameronis and B. liturata have been widely and repeatedly recorded from the extreme south and south west of South Africa -the former also from Lesotho and central Namibia (Fig. 7b), suggesting that it is more widespread, and the latter surprisingly has alledgedly been recorded from the Victoria Falls area in Zimbabwe (Fig.  12b), requiring further investigation.
With strongly western distributions within southern Africa and associated with semiarid to arid areas are: B. karroensis (Fig. 12a) apparently restricted to the Nama-Karoo; B. namibensis (Fig. 14a) apparently restricted to the arid areas of Namibia; B. olivata (Fig.  14c) apparently principally restricted to the arid areas of Namibia but also recorded from the southern Kalahari; B. venusta (Fig. 16c) apparently the Nama-Karoo of Namibia and Angola; B. zinni (Fig. 16d) principally Nama-Karoo and southern Kalahari.
Species with strictly coastal distributions (Fig. 17) are: B. albata along the coast of the Namib Desert to its southern extension in Namaqualand; B. arnoldi and B. harenarum along the south and south east coasts of South Africa; B. fraudulenta along the east coast of South Africa from the south into Mozambique.
Widespread species in northern southern Africa are: B. ulula (Fig. 16b) and B. cultrifera (Fig. 7e), not known from further north; and B. moebii (Fig. 12e), known to extend northwards to Tanzania and recorded from Ethiopia in northeast Africa but not from northwest Africa.
Another apparently northern species but less widespread with repect to longitude is B. regnata (Fig. 14d).
Two species apparently restricted to South Africa but not found in the karroid areas are B. capicola (Fig. 6d) and B. sibilans (Fig. 14f).
Comments on the distributions of the other species would be premature.
Bembix visit flowers not only to obtain nectar for adult nourishment but also when hunting. Recorded flower associations cannot therefore be assumed to be for imbibing nectar. As nectar seekers they are polyphagous.
Bembix typically prey on flies (Diptera) of various families. Unusual for the Afrotropical Region is Bembix regnata Parker which was found by Benson (1934) provisioning with butterflies (Lepidoptera) of three families in East Africa. In this regard it is of note that Matthews (1973, 1975) recorded considerable radiation with respect to prey taken by Australian Bembix. Of the 22 species studied 14 took only flies, however, one took damselflies (Odonata) in addition to flies, one bees and wasps in addition to flies, three only bees, primarily stingless bees of the genus Trigona (Apidae), one only tiphiid wasps, one only damselflies and yet another only antlions (Neuroptera). Species hunting flies seem to show little selection with respect to fly family, the qualifying criterion being apparently one of size and habitat.
Bembix hunt their prey on the wing. They tend to find a good source of flies, often decaying organic matter such as faeces and corpses, in the case of B. arnoldi ocean tion with the preparation of the manuscript given to SKG after the death of FWG and meticulous reviewing of the submitted manuscript -Wojciech J. Pulawski, California Academy of Sciences, San Francisco.