Culex (Culex) vansomereni Edwards

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 : 93

Culex (Culex) vansomereni Edwards

subspecies draconis Ingram & de Meillon, 1927 —original combination: Culex draconis (subspecific status by Edwards 1941). Distribution: Republic of South Africa ( Ingram & de Meillon 1927).

subspecies elgonicus Edwards, 1941 —original combination: Culex vansomereni ssp. elgonicus . Distribution: Ethiopia, Uganda ( Wilkerson et al. 2021).

subspecies vansomereni Edwards, 1926a —original combination: Culex vansomereni . Distribution: Democratic Republic of the Congo, Ethiopia, Kenya, Liberia, Mozambique, Republic of South Africa, South Sudan [but not Sudan ( Simsaa et al. 2021)], Tanzania, Uganda, Zimbabwe ( Wilkerson et al. 2021). The record of Lewis (1956) is from Gilo in South Sudan.

Subspecies draconis was originally described as a distinct species ( Ingram & de Meillon 1927) and interpreted as a subspecies of vansomereni by Edwards (1941). This subspecies differs from the type form in having a pair of submedian yellow stripes on the posterior half of the scutum and sometimes an ill-defined pair of curved lines of yellow scales on the anterior half. In males, the lateral plates of the phallosome are of a slightly different shape with more numerous denticles, and more importantly, the subapical lobe of the gonocoxite is not divided, seta g is larger, as long as seta f, and seta h is noticeably flattened. Based on information provided by Jupp (1996), it seems likely that the two forms occurs in sympatry in South Africa.

Subspecies elgonicus was described by Edwards (1941) from a female and two males (with dissected genitalia) collected by G. R. L. Hancock (Mattingly 1956) at high elevation (6,500 ft., about 1,980 m) on Mt Elgon in Uganda. Edwards indicated that elgonicus resembles the typical form “in nearly all respects” and distinguished it based on differences observed in the male genitalia, including the phallosome with slightly different lateral plates (with a longer and more incurved ventrolateral process and a larger number of marginal denticles), subapical lobe less distinctly divided, seta d present, setae d and e small and slender, seta f broader distally and noticeably separated from setae d and e and seta g larger, broader and as long as seta f. Catalogers, beginning with Stone et al. (1959), indicate that elgonicus has been recorded from Ethiopia without providing the source of the record. If elgonicus does in fact occur in Ethiopia, then it is more widely distributed and obviously distinguishable from the type form.

Available evidence suggests that Cx. vansomereni is a complex of species. Hopkins (1952) observed that “The larvae of this species vary very considerably, particularly in the degree of sclerotization of the head and siphon, the siphonal index, and the number of comb-scales. Examination of a long series of specimens from Nairobi (the type-locality of the species), South Africa ( ssp. draconis Ingram and de Meillon ), and various localities in Uganda ( ssp. vansomereni ) has shown that though the majority of the specimens from South Africa and of those from high elevations in Uganda (6000–7000 ft.) are of the form with strongly-sclerotized and long siphon, and of those from Nairobi and from low elevations (5000 ft. and below) in Uganda of the form with short, weakly-sclerotized siphon, the differences are not constant; in at least one of the Uganda localities specimens of both forms and also intermediates have been found breeding in the same pool. According to Edwards (1941), larvae of vansomereni draconis are separable by their longer siphon (index about 6), the fact that the “coronet” of the subapical spines on the siphon is divided into dorsal and ventral groups, and by the subventral tufts of the siphon being double and scarcely longer than the diameter of the siphon.” This statement, however, pertains only to larvae, which have not been studied in detail. When other larval features, e.g. branching of the dorsal head setae and anal papillae, topographic and distributional data, with indication of sympatry, and particularly differences in structures of the male genitalia are considered, we conclude that the three described forms are likely to be different species; thus, subspecies draconis and elgonicus are herewith elevated to specific status: Culex (Culex) draconis Ingram & de Meillon, 1927 and Culex (Culex) elgonicus Edwards, 1926a . Both nominal forms are currently listed as species in the Encyclopedia of Life.