Records of the Breeding of ‘Saltwater Anopheles gambiae’ at Inland Localities in Southern Africa

Abstract

RECENT^1–5 work has shown that at least four genetically distinct forms comprise the A. gambiae complex. Paterson⁶ has outlined arguments for regarding them as separate species. On the eastern half of Africa three species occur, ‘saltwater A. gambiae’ and the two freshwater-breeding species, species A and species B (= group A and group B³). These forms are apparently morphologically inseparable, though the frequency of females bearing four white bands on their palps, as against three, is usually much higher in populations of ‘saltwater A. gambiae’ than of the two freshwater-breeding species. Identification of the species is best achieved by performing crossing experiments with ‘type’ colonies of the different species. Interspecific crosses produce sterile F₁ males^1–4 with testes and accessory glands reduced to varying degrees according to the cross and its direction. In crosses between ‘saltwater A. gambiae’ and either species A or species B, F₁ sex ratios supply further information^1,2,4, but crosses between the two freshwater species usually produce normal sex ratios⁴. A physiological test (salinity-tolerance test) is available⁷ to distinguish first stage larvæ of ‘saltwater A. gambiae’ from those of either species A or species B.