Culex (Culex) grahamii Theobald

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 : 84-85

Culex (Culex) grahamii Theobald

subspecies farakoensis Hamon, 1955 —original combination: Culex grahami [sic] var. farakoensis (subspecific status by Harbach & Howard 2007). Distribution: Southern Mali (Hamon 1955).

subspecies grahamii Theobald, 1910 —original combination: Culex grahamii [nomen novum for Culex pullatus Graham, 1910 ]. Distribution: Angola, Benin, Burkina Faso, Cameroon, Central African Republic, Côte d’Ivoire, Democratic Republic of the Congo, Ghana, Guinea, Kenya, Liberia, Madagascar, Mali, Nigeria, Republic of the Congo, Senegal, Sudan and South Sudan, The Gambia, Togo, Uganda ( Knight & Stone 1977; Wilkerson et al. 2021).

Graham (1910) described the male and female of this species (as Cx. pullatus ) from specimens collected in the vicinity of Lagos, Nigeria ( Stone et al. 1959; Townson 1990). The larva was described by Wesché (1910), as Cx. pullatus , from specimens collected around Lagos, described by Macfie & Ingram (1923) from specimens collected in the vicinity of Accra, Ghana (as Gold Coast) and by Hopkins (1936, 1952) from undisclosed localities, except for reference to specimens described by Macfie & Ingram. Hamon (1955) described farakoensis from specimens collected “aux cascades de Farako, Cercle et Subdivision de Sikasso, Soudan Français ” (at Farako waterfalls, Sikasso Cercle and Subdivision, French Sudan = Mali). Farako Waterfalls are located about 30 km east of Sikasso in Sikasso Cercle, which is one of seven administrative subdivisions of the Sikasso Region of southern Mali. Based on this, the type locality of farakoensis that is listed as “Farako, Sikasso, French Sudan ” in the catalogs of Stone et al. (1959), Knight & Stone (1977) and Wilkerson et al. (2021) must be corrected to Farako Waterfalls, Sikasso Cercle, Mali (formerly French Sudan). The listing of Nigeria in the distribution given by Wilkerson et al. (2021) appears to be in error.

Hamon (1955) provided a brief description of farakoensis , stating that the adults are “almost identical to the typical form and probably not separable with certainty. Male terminalia [genitalia] do not show any difference…” and the “general morphology [of the larva] is that of Cx. grahami [sic] except for the eighth abdominal segment…” (translated from the French). Hamon recorded the following distinctions: Comb with 13–19 spine-like scales, siphon index 7.9–10.4, pecten with 6–9 simple spines, seta 1-S with about 16 setae (this is misleading as the illustration provided includes a ventral row of 12 setae beyond the pecten and a lateral row of 5 setae on the distal half of the siphon) with 2–4 branches and the 8 proximal setae at least as long as the diameter of the siphon; anal papillae 2.5–4.0 times as long as the saddle. Hamon stated that the dorsal pair of anal papillae were usually longer than the ventral pair, but the illustration shows the ventral pair are longer than the dorsal pair. In the typical form, these morphological traits, based on the descriptions of Wesché (1910), Macfie & Ingram (1923) and Hopkins (1936, 1952), are characterized as follows: Comb with 14–25 spine-like scales, siphon index 12–15, pecten also with 6–9 simple spines, seta 1-S with about 4 setae (6 are illustrated by Hopkins), minute, with 1–3 branches, one seta inserted within the pecten; anal papillae slightly longer than the saddle, usually equally long or dorsal pair slightly longer. Thus, only three of these characters are distinctive for farakoensis , i.e. the significantly shorter siphon, the more numerous and longer siphonal setae all borne distal to the pecten and the greater length of the anal papillae. However, the comb scales illustrated for farakoensis appear to differ from those illustrated for the typical form. The lateral spicules progressively increase in length to the sides of the median apical spine in farakoensis whereas in the typical form they comprise lateral fringes of equal length borne proximal to a stronger apical spine.

Hamon (1955) concluded the description of farakoensis with the following observation: “This species [ farakoensis ] was already known from various places of the A. O. F. [Afrique-Occidentale française (French West Africa)], but the only locality having given us larvae identical to the description of Hopkins is Danané (Forest Zone of lower Côte d’Ivoire). All the larvae collected in the savannah zone: Agba-titoé ( Togo), Thiès ( Senegal), Bobo Dioulasso ( Upper Volta) [ Burkina Faso] and in various sites of Casamance [ Senegal] have in fact the color and chaetotaxy of the typical form but their siphon indexes rarely exceed 11 [translated from the French].” This indicates that the siphon index of farakoensis may be slightly greater than noted in the description, but it is still smaller than that of the typical form. This observation, the morphological distinctions noted above and the apparently close association with savannah strongly suggest that farakoensis is likely to be genetically distinct from Cx. grahamii sensu stricto; accordingly, this nominal form is formally elevated to species status: Culex (Culex) farakoensis Hamon, 1955 . Culex farakoensis is currently listed as a species in the Encyclopedia of Life, however the date of authorship for the former species needs to be corrected from 1954 to 1955.