Dry Season Biology of Anopheles gambiae Giles in the Sudan

Abstract

COLLECTIONS of mosquitoes have been made regularly throughout the dry season in the desert west of Omdurman, Sudan, by means of pyrethrum-spraying, well-traps and hand catching. The results indicate that adult female Anopheles gambiae (sp. B ?) Giles survive throughout the dry season, but with a change in their physiology and behaviour. The insects were found to hide in dwelling huts (87.7 per cent), in cracks down dry wells (8.5 per cent), in disused or ruined houses (3.2 per cent) and in rabbit and rodent burrows (0.5 per cent). Dissection showed that 77.1 per cent of the nulliparous females captured were engorged with blood. Of these, 90.6 per cent contained human blood. The ovaries evidently undergo only one gonotrophic cycle during the dry season, developing extremely slowly so that, when the rains come, the gravid females are ready to oviposit. These mosquitoes are apparently unable to lay eggs during the dry season.