Studies on the mechanism of DDT resistance in Culex pipiens fatigans. Lipids of susceptible and resistant strains.

The mechanism of DDT resistance in Culex pipiens fatigans is poorly understood. Earlier studies indicated that the dehydrochlorination of DDT does not explain resistance in this species. Studies on the role of lipids as a mechanism of resistance included the estimation of lipid content and the determination of the proportions of different classes of lipids in the larvae of susceptible and resistant strains. There was no evidence of any correlation between the lipid content and DDT resistance in this species and the proportions of neutral lipids, phospholipids and fatty acids of different strains did not indicate any consistent correlation with DDT resistance.Within one strain, the larvae containing the higher amount of lipids were able to resist better the toxic effect of DDT. Analysis of fatty acids of the larvae that survived and died as a result of treatment with DDT did not reveal any difference.Neither p,p'-DDT nor o,p'-DDT at sublethal concentration affected the lipids of the larvae of susceptible and resistant strains.