Abstract
It has been known, as an actual phenomenon, that during a contact-test on an insecticide film the KT_<50> values (the measurement of insecticidal potency to test insects) often unexpectedly fluctuated. Using house flies an investigation was attempted on this phenomenon. It was experimentally confirmed that test insects are more susceptible to insecticide residues when its treated surface contains a minute amount of moisture. The relationship between the KT_<50> values and the amount of the moisture showed an inverse correlation. Such an instability of knock down effect due to the moisture, is the most evident in both cases of DDVP and Dibrom regardless the formulation of the insecticide when applied on absorptive materials such as filter paper or veneer plate. If applied on a glass plate, however, similar effect was not recognized.
