Larval habitats of the primary vector of malaria in subSaharan Africa, Anopheles gambiae, were examined in western Kenya locales. The habitats are often small, ephemeral, and formed by human activities. Mosquito production was highly variable across habitats and unrelated to habitat size or proximity to human dwellings. Possible constraints on larval development included presence of predators, and habitat stability, and studies in artificial habitats suggested that algal food resources could be limiting in newly formed habitats. These factors are discussed within the overall ecology of malaria transmission in the region.