The Adsorption, Distribution, and Site of Action of DDT in DDT-Resistant and DDT-Susceptible House Flies Using Carbon Labelled DDT14

Abstract

Influence of the area of contact, duration of contact, locus of application, strain of fly, hemolymph circulation and death on the adsorption and distribution within the insect of topically applied DDT and on the resulting mortality was studied using adult male Musca domestica. Dosages of from 0.05 ug to 1.5 ug of para-para-DDT were applied either as dilute or concn. solutions in benzol, to the tibio-femoral joint of one metathoracic leg. the labella, the gena or the supra-oesophageal ganglion. Carbon14 labelled DDT made possible the measurement of resulting radio-activity in various body parts. Activity was detectable in the hemolymph 30 seconds after external application but did not build up. The critical factor was the amount that accumulated in the head. Accumulation in the head was slower and less from loci far removed from the head, smaller areas of contact, shorter exposures, impeded circulation, after death, and in the DDT resistant strain. Mortality paralleled this accumulation up to a point; 0.05 [mu]g on the head-ganglion equalled in effect 1.5 [mu]g. on the leg. Less material was adsorbed and more appeared in the feces of the resistant strain. Differences in strain resistance were less for applications to the labella and least for applications to the head-ganglion. No radio-activity was detectable in the respired air. It is observed that loci of application will influence observed lethal doses and observed resistance, and that greater sensitivity in bioassay would result from the use of the most sensitive loci of application.