The biology of anopheline mosquitoes is being studied in relation to the capacity of these vectors to transmit malaria. Molecular, biochemical, and immunological studies are seeking to describe mechanisms of malaria parasite development in the mosquito host with emphasis on the behavior of ookinetes, oocysts, and sporozoites. Probes are being developed to facilitate characterization of cytogenetically distinct populations of Anopheles gambiae in Mali, West Africa. Studies on the composition of the mosquito larval diet seek to identify microorganisms which might prove useful as carriers of biologically active larvicidal agents. Systems for cloning and transposing genes into mosquito germ lines are being developed to assist in generating vector species unable to transmit malaria parasites in nature. Parasiticidal mechanisms from within mosquitoes and from other organisms are being evaluated for introduction into vector species. The ability to identify, clone, and transpose genes which regulated refractory mechanisms should permit development of mosquito populations incapable of transmitting malaria for eventual use in malaria control schemes.