A method of killing mosquito larvae and particularly the species comprising Culex tritaeniorhynchus, Cx. pseudovishnui, Cx. (Cx) sp., Cx. (Lutzia) sp. and Anopheles hyrcanus group which comprises in allowing Chilodonella uncinata as a ciliated protozoa to be present in said host larvae, allowing the ciliated protozoa to form a hole in the wall of the larvae and to enter into the haemocoelomic cavity of the larvae and to thereby allow the ciliate to feed on the host larvae and simultaneously allowing the host larvae to grow and allow a multiplication of the ciliate, and whereby the multiplied ciliates kill the host larvae.