The Resistance of Insects to Insecticides. Some Differences Between Strains of House Flies1

Abstract

Cholinesterase activity, O2 consumption, and mortality response to DDT were detd. in 6 susceptible and 3 resistant strains of house flies, Musca domestica. Considerable variation in cholinesterase activity was found among the susceptible strains. It is therefore questionable whether the lower activity occasionally observed in resistant strains is a true strain difference. Differences in O2 consumption were statistically significant when 1 susceptible strain was compared with 1 resistant strain, but were not significant when 3 susceptible strains were compared with 3 resistant ones. Six susceptible strains showed considerable variation in mortality when treated with DDT topically.