Anopheles culicifacies is the major vector of rural malaria in the plains of India. Cytogenetic analysis of polytene chromosomes revealed that A. culicifacies is a complex of five sibling species designated as A, B, C, D, and E. Each sibling species has its own distribution pattern which is influenced by the environment. Sibling species differ in their larval and adult biology, response to insecticides, and capacity to transmit the disease. This knowledge has been applied in malariogenic stratification and the selection of cost-effective strategy in fighting malaria in India.