IN a letter published in NATURE of January 5, 1935 (135, 34), we directed attention to the discovery, at Hayling Island (Hampshire), of a strain of the mosquito Culex pipiens exhibiting certain abnormal characteristics (notably the ability of the females to lay fertile eggs upon a blood-free diet) which Roubaud has designated by the adjective autogenous. Such autogenous strains of C. pipiens had previously been recorded only from France1, Germany2, Greece3, Hungary3 and Malta3. Roubaud, who considered his autogenous strain and the ordinary (anautogenous) strain to be morphologically identical4, indicated their biological differences by naming them respectively Culex pipiens autogenicus and Culex pipiens pipiens5.