Abstract
Experiments were made to produce radioactive mosquitoes of a laboratory bred colony of Culex pipiens s.l. from Tokyo. Among the three methods tested here, best results were obtained by rearing the fourth instar larvae with the water containing P^<32>. A series of experiments were repeated to rear the larvae with various strength of radioactivity ranging from 3.0μc to 0.01μc, and the radioactivity of the females emerged from them were counted for the period of 15 days. It was observed that the readings of the counts increased as the concentration of P^<32> in water was higher, and even with the minimum lot reared in water of 0.01μc it gave 487 to 125 cpm per mosquito for the period from 1 to 15 days after emergence. High mortality of pupae was seen in the lots reared in waters containing the doses above 1.0μc. The female mosquitos fed with syrup containing 1.0 and 2.0μc of P^<32> per ml. gave the average readings of 84.9 cpm and 171.8 cpm respectively, but the counts were lower than those obtained by the above method. Females which were engorged with the blood of a mouse to which 100μc were injected intraperitoneally 10 hours before, also gave the average count of 113.9μc above the background counts.
