Anopheles arabiensis, (Patton, 1905) (Patton, 1905)

Harbach, Ralph E. & Wilkerson, Richard C., 2023, The insupportable validity of mosquito subspecies (Diptera: Culicidae) and their exclusion from culicid classification, Zootaxa 5303 (1), pp. 1-184 : 18-19

Subspecies arabiensis

Patton (1905) described subspecies arabiensis from Ulub Camp and Crater, West Aden Protectorate [ Yemen] from an unspecified number of adult males, adult females and larvae. No type specimen was designated and type material is presumed to be lost or never existed. White (1975), when he removed arabiensis from synonymy (synonymy by Hamon et al. 1966) with vexans and elevated it to a subspecies of vexans , reported finding a male and two females of arabiensis from Aden, “topotypic arabiensis material”, in the collection of the Natural History Museum, London, but did not designate a neotype.

Patton’s (1905) original description of arabiensis is vague and roughly follows the description of vexans by Becker et al. (2020) paraphrased above. Confusingly, Patton stated: Thorax “with a dark line down the center and two at the sides. Abdomen brown with apical black bands. … Male genitalia, basal lobes narrow... apical segment thin and somewhat club shaped.” The apical black abdominal bands probably refer to contrast with the basal pale bands in all other taxa related to vexans . Edwards (1921d) apparently listed it as a synonym, perhaps “in part”, in a treatment of vexans : “(?) Culex arabiensis, Patton (adult, not larva) [alternatively, this could mean he thought the larva was a different species].” Edwards (1925) listed it with the “ vexans series” as “ A. vexans, Mg. (=? arabiensis, Patton. ).” A year later, Edwards (1926b) explicitly listed arabiensis as a synonym of vexans , but then in 1941 he placed it as a species of the vexans group.

Edwards (1941) stated that arabiensis was “Distinguished from other Ethiopian species of the subgenus [ Aedimorphus ] by the combination of the following features: basally-ringed tarsal segments, dark-scaled wings, broadly banded abdomen, and pale posterior surface of middle tibiae. A. arabiensis is very closely related to the Palearctic A. vexans Mg. , from which it differs in having the male palpi rather shorter; abdominal bands in both sexes broader and not emarginate in the middle; middle tibia dark above (in all European and Central Asian females of A. vexans examined the middle tibia is conspicuously pale above as well as posteriorly).” Further, abdominal “tergites [terga] 2–6 with broad creamy-white basal bands, 2–7 with lateral whitish patches extending most of their length, 6 and 7 with narrow pale apical bands; sternites almost entirely pale scaled.”

Lewis (1945) added that the larva has seta A [7-C] with 7 or 8 branches, seta B [6-C] single and seta C [5-C] single or double. “Comb a patch or irregular row of 8–12 sharp-pointed spines with small basal denticles. Siphon with index about 2.5... pecten reaching slightly beyond middle… of the last 1–3 teeth [spines] usually 2 larger and widely spaced.... Gills [anal papillae] subequal, lanceolate, much longer than saddle.” The relatively long pointed anal papillae are a particularly obvious characteristic.

Hopkins (1952) expanded the description of Lewis (1945) and provided an illustration. “The only other Aëdes larvae with the comb composed of a small number of spines... head-setae B and C [6- and 5-C] single and the last 2–3 pecten spines wider-spaced are cumminsi , fowleri and durbanensis . From the first two of these the larva of arabiensis is easily separated... by the shape of the ‘gills’ [anal papillae].”

Carpenter & LaCasse (1955), without comment, listed nocturnus , arabiensis and nipponii as synonyms of vexans . Perhaps those authors were unaware of or disagreed with the recognition of nocturnus and nipponii as subspecies of vexans by Bohart & Ingram (1946b).

The story became less clear to us with Muspratt’s (1955) description of vexans from Transvaal, South Africa, and its comparison with vexans from England and the USA (Washington State). Muspratt pointed out some differences, such as “the tibiae of the former [ South Africa] are practically all dark except for the narrow basal pale bands and apical spots, whereas the tibiae of the latter [ England; USA] are extensively pale posteriorly...” [as described for arabiensis from Yemen]. Also, “on the South African form the basal pale bands of the abdominal tergites [terga] are not narrowed in the middle, thus being as described for arabiensis ...”. Jupp (1996) illustrated and keyed, from South Africa, as vexans , a taxon with narrow basal emarginate abdominal tergal bands and with the sterna not all pale but with dark markings. This suggests two species in South Africa, and we think neither is arabiensis , which is distributed in northeastern Africa and Arabia.

Mattingly & Knight (1956) treated arabiensis from Arabia as a species but wrote: “This is very closely related to the holarctic [sic], Oriental and Australasia Aë. vexans Meigen , of which it is possibly no more than a subspecies…”.

Hamon et al. (1966) considered all observed differences as only variation. Regarding this, White (1975) wrote: “Having not seen the types of either arabiensis or sudanensis [a synonym of arabiensis ], the former having been lost, Hamon et al [sic] (1966:373) formally synonymised both with vexans s. str. ” As noted above, White (1975) removed arabiensis from synonymy with vexans and elevated it to subspecific rank, and affirmed that sudanensis Theobald, 1911b was a junior synonym of arabiensis . He also listed the known distribution of vexans arabiensis as Aden, Gambia, Mauritania, Nigeria, Saudi Arabia, Somalia, South Africa (Transvaal) [we think doubtful] and Sudan. Since that time, vexans arabiensis has been identified in a number of studies, and has been implicated as a possible vector of the Rift Valley Fever virus in northeastern Africa and Arabia ( Miller et al. 2002; Mondet et al. 2005; Fall et al. 2011; Clements 2012; Krtinić et al. 2013; Francuski et al. 2016; Mohamed et al. 2017; Azari-Hamidian et al. 2019).

Mohamed et al. (2017), using the keys in Edwards (1941) and Hopkins (1952), found vexans arabiensis to be very common in collections made in the Republic of Sudan. Of special note was the presence of two larval types (“X” and “Z”), both of which keyed to vexans arabiensis in Hopkins (1952). Since no larvae were reared to the adult stage, it is not known which might be true arabiensis . Nor is it known if the adult females collected during the study belonged to more than one species.

Given the distinctive morphological characters of the adult female and larval stage of subspecies arabiensis , we think it should be formally afforded species status: Aedes (Aedimorphus) arabiensis ( Patton, 1905) . Synonym: Culex sudanensis Theobald, 1911b . Aedes arabiensis is currently listed as a species in the Encyclopedia of Life.