The mosquito Anopheles gambiae is the primary vector of malaria in equatorial Africa. Contrary to what is generally understood, adult An. gambiae have two hosts: vascular plants for sugar and mammals for blood. New evidence indicates that plants and mammals may be equally important to population growth, reproduction, and survival of An. gambiae. Males feed only on plant sugar and may be absolutely dependent on it to survive and inseminate. Females, in turn, are dependent on male insemination for their own reproduction, and in addition require mammalian blood to develop eggs. Yet, females ingest not only blood but also plant sugar, in some unknown ratio whose effects on survival and egg production are obscure. To elucidate the role of this little-studied interplay between two nutrients in the two sexes, it is necessary to start with groundwork of biochemical and behavioral information. That information should come from natural populations where malaria is holoendemic and from captive mosquitoes allowed to perform in free-running systems. It is proposed, here, that field work be done in Kenya and Tanzania, and that captive work be conducted both in E. Africa and North America. The groundwork to be laid will indicate 1) how frequently males and females feed on sugar, 2) whether sugar-feeding frequency differs between extremes of season and biogeoclimatic zone, 3) which species of plants bear the nectades, or host the honeydew-producing homopterans, that provide the sugar, 4) whether lipid, glycogen, and protein reserves build up among adults that become reproductively functional in the field, 5) whether sugar-feeding frequency changes with age, female gonotrophic state, or availability of blood and oviposition sites, and 6) to what extent dietary sugar affects male insemination capacity. If plants prove to play a major role in An. gambiae biology, two investigations will be warranted: measuring the impact of plant sugar on its lifetime reproductive success and measuring its long-term impact on vectorial capacity. If male performance is closely tied to sugar availability, and therefore to the composition of plant communities, this information will be vital to the success of genetic methods of malaria control. If vectorial capacity is affected strongly by sugar availability, malaria transmission can be impeded or interrupted through manipulation of vegetation. This vector species delivers malaria to most of the approximately 300- 500 million people infected worldwide, so either approach is likely to make a significant contribution.