Ecnomus mennellisp.n. from Lake Naivasha, Kenya, belongs to thenatalensis‐group.E. thomassetiwas also found at the lake, and these are the first records of Trichoptera from Naivasha. Adults and larvae of both species were collected, and an analysis of the gut contents of the larvae showed them to be mainly predator y on small invertebrates. The ecological requirements and distribution of the African species ofEcnomusare discussed.