Resistance to pyrethrins and DDT in a strain of houseflies Musca domestica L. I. The sorption of a synthetic [14C] pyrethrin I

A [14C] pyrethrin I mixture, consisting of a mixture of the naturally occurring ester and one of its diastereoisomers, has been synthesised. Penetration of this labelled material in a strain of houseflies that has shown resistance to pyrethroids in the field, has been studied. It has been shown that the resistance of the flies, which also show a high degree of tolerance to DDT, is due in part to reduced penetration of the pyrethrin I.