Mosquito production and species succession from an area of irrigated rice fields in The Gambia, West Africa.

The succession of mosquito species and their abundance was observed through one cycle of dry-season irrigated rice cultivation near Bansang in The Gambia. The study covered a 21-week period, February-June 1975. Mosquitoes were sampled using a single suction trap located in a dry field beside the rice fields. Few mosquitoes were present before irrigation began. Anopheles gambiae s.1., A. rufipes and Culex neavei reached peak numbers 4 weeks after full-scale irrigation began and then declined in abundance. These three species were amongst the four (with Culex poicilipes) most abundant mosquitoes taken by the suction trap, comprising 85.4% of the total captures. Anopheles pharoensis, Culex ethiopicus and C. poicilipes were most common around the middle of the rice-growing cycle 6-13 weeks after the start of full irrigation and showed more extended peaks of abundance. Anopheles ziemanni alone reached maximum numbers as the rice crop neared maturity. C. antennatus, Mansonia africana and M. uniformis were present throughout the period of observations, but their numbers showed little relation with the cycle of the rice growth.