Duration of sterility induced in males of the tropical house mosquito, Culex pipiens fatigans Wiedemann, by the chemosterilants apholate and tepa.

Various alkylating and non-alkylating agents are known to induce sterility in Culex pipiens fatigans, but the duration of the sterilizing effect they produce had not so far been studied for this species. The authors therefore investigated the duration of sterility induced by the alkylating chemosterilants apholate and tepa in C. p. fatigans, second-instar larvae being exposed to 10 ppm apholate or pupae to 3570 ppm tepa. They found that, in experiments in which treated males were mated once only, both apholate and tepa induced sterility lasting at least 48 days. However, in experiments in which males were mated once weekly for 6 weeks apholate-treated males showed a slight recovery from the early sterilizing effect. On the other hand, tepa was found to be very effective in inducing lasting sterility throughout the 6 successive matings. The probable reasons for the recovery from sterility of apholate-treated males and the more lasting sterility of tepa-treated males are discussed.