THE Course of poisoning of normal and pyrethrins-resistant house flies by pyrethrins-piperonyl butoxide residues: a kinetic analysis
1964
SNYDER, F.M. | CHADWICK, L.E.
Virgin female house flies, Musca domestica L., one day of age, were exposed at 32° C for measured periods of time to deposits on glass of six concentrations of pyrethrins (Py) and to 42 Py-piperonyl butoxide (PB) mixtures. The percentage mortality at 18 to 20 hr after exposure was recorded, and the duration of exposure required for 50% kill (Lt₅₀) was calculated for each treatment from the regression of probit kill on log exposure time. Comparison of the Lt₅₀'s for these normally susceptible flies at different Py concentrations indicated that the apparent order of the toxic reaction was about 4.5 with residues that contained Py alone. In the presence of PB, the apparent order was reduced progressively approximately to 2. These observations are interpreted in support of the hypothesis that flies possess a mechanism for detoxifying Py, and that PB exerts its synergistic action by interfering with the detoxication process. Similar data from a strain of flies selected for over 90 generations for Py-resistance suggest that the selected strain possesses a more active detoxifying mechanism, which need not differ qualitatively from that present in the unselected population. The development of direct biochemical and physiological evidence in reference to these problems is urged.
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