Following continued adult selection for dieldrin resistance of the El Salvador strain (RR) of Anopheles albimanus, F1, F2, and backcross progenies were produced by a method of sib-mating. The source of the homosygous susceptible mosquitoes was a colony of A. albimanus from Panama (SS). Larval progenies from individual females were tested for survival following 24 hours of exposure to 0.01 or 0.1 ppm dieldrin suspensions.
The 0.01 ppm dosage killed all SS, but not the SR/RS or RR larvae. The 0.1 ppm dosage killed SS and about 88% of the SR/RS larvae, but none of the RR larvae.
The mortalities in test crosses showed close agreement with those expected on the basis of monofactorial inheritance of dieldrin resistance. The results also are in agreement with Davidson's conclusion that dieldrin resistance in A. albimanus larvae is “semi-dominant.”