DENSITY-INDEPENDENT FEEDING SUCCESS OF MALARIA VECTORS (DIPTERA, CULICIDAE) IN TANZANIA

The possibility of density dependent feeding success in the African ma laria vectors Anopheles gambiae Giles (sensu lato) and A. funestus Gil es was investigated by examining the gonotrophic status of mosquitoes from 423 collections made in a Tanzanian village. Up to 500 mosquitoes were caught in any single 35 minute indoor resting collection. Estima tes of the total numbers of mosquitoes resting were made by removal sa mpling. These indicated that the efficiency of resting collections dec reased with increasing mosquito population. Of 1904 mosquito blood mea ls tested by ELISA, 95% were of human origin. There was no decrease in the proportion of mosquitoes fully fed at high population densities a nd the only demonstrable avoiding action by hosts in response to high densities of mosquitoes was the increased use of bednets during the we t season. The late biting cycle of these mosquitoes precludes many oth er density-dependent host defence mechanisms because the hosts are asl eep at the time of attack. African malaria vectors have evolved with m an and perhaps their evasion of density-dependent host responses has r einforced their preference for human blood.