The preliminary trials of the aqueous extract of Citrullus colocynthis fruits on the larvae (L4) of two species of mosquitoes (Culex pipiens and Culiseta longiareolata) showed the efficacy of this extract on the larvae (L4) of the two species. The sublethal doses (10, 50 and 100 mg/l) were tried on the reproductive performances to the two species studied. The results showed that there was a reduction in female fertility of the emerged larvae exposed to these doses. For Culex pipiens, the number of eggs laid was 409, 261 and 123 eggs respectively, with the doses 10, 50 and 100 mg/l, while at Culiseta longiareolata, pundits were 431, 302 and 150 eggs. Knowing that in the control females, the rate of fertility was high compared to treated individuals; the number of eggs laid was 598 and 612 respectively for the first and second species.