Abstract
In order to evaluate the insecticidal effect of permethrin and phthalthrin vapor on cockroaches, an apparatus was invented to keep constant the pyrethroids' concentration in air and provide a pyrethroid vapor or mist strong enough to knock down cockroaches. A relationship between the pyrethroid concentration in the air and KTX50 obtained by using this apparatus revealed a certain curve which has a point of inflection at a concentration around 100 μg/l. These relation curves gave a vivid account of the characteristic of each insecticide. Phthalthrin's remarkable KD effect upon cockroaches occurred in its higher concentration in ari, while permethrin showed prominent kill and KD effects through a wide concentration range. In all of these tests male cockroaches were more susceptible than female.
