Variation in cuticular hydrocarbons among strains of Anopheles (Cellia) stephensi Liston possibly related to prior insecticide exposure

Cuticular lipids were extracted in hexane from the females of four strains of Anopheles stephensi and separated by capillary gas chromatography. When the chromatograms produced were quantified and compared by discriminant analysis, compositional variations in the hydrocarbons indicated that two of the strains, 'Russ' (originally isolated in the former U.S.S.R.) and 'Iraq' (from Iraq), both of which were susceptible to DDT and malathion, could be confidently separated from 'Beech' from India and 'St Mal' from Pakistan, both of which were resistant to DDT and malathion. A high degree of hydrocarbon segregation between each of the four strains might be associated with geographical variation. It appears that there are significant and real differences in the hydrocarbons of these strains and these may be at least partially related to genetic alterations resulting from prior insecticide exposure. However, far more analysis is required if any relationship with prior exposure is to be confirmed.