The biology and distribution of the 2 Malagasy Stegomyia species, Aedes aegypti and Aedes albopictus, is updated and reported. Aedes aegypti is present in the western and southern regions and Ae. albopictus in the east and on the high plateau. Some unusual locations are noted. The ranges of Ae. albopictus and Ae. aegypti on Madagascar overlap only slightly. Aedes aegypti is present in the west and in the south, while the Ae. albopictus distribution area is in the east and on the central high plateau. Climatic factors (number of dry months, annual rainfall and temperature), rather than competitive interactions, appear to be the major determinants of the distribution of these species. Aedes aegypti is just slightly anthropophilic, contrary to Ae. albopictus. Babanki virus and MMP 158 virus were isolated from Ae. aegypti; no virus has been isolated from Ae. albopictus.