Abstract
A strain of housefly, YBOL, highly resistant to pyraclofos ((R, S)-[O-1-(4-chlorophenyl)pyrazol-4-yl O-ethyl S-n-propyl phosphorothioate], Boltage[○!R]), was established from a colony collected from 3rd Yumenoshima after selection with this chemical. The reciprocal crosses between the resistant (YBOL) and susceptible strains showed that pyraclofos resistance was incomplete dominance. Linkage group analysis of the dominant factors responsible for this resistance was carried out by the F1 male backcross method using a susceptible multichromosomal marker strain. The dominant factors for pyraclofos resistance were located on the 2nd, 4th and 5th chromosomes. The factors on the 2nd chromosome contributed the greatest to pyraclofos resistance, followed by those on the 5th chromosome and then the 4th chromosome. In pyraclofos resistant strain, it was revealed that the male determinant factor (M) existed on the 3rd chromosome.
