Haploid males of the black pineleaf scale (Nuculaspis californica [Coleman]) growing naturally on their ponderosa pine host trees suffer higher mortality than the diploid females; thus secondary sex ratios change through the life history. Serial dilutions of malathion sprayed on the newly settled scales caused further differential male mortality. The male/female ratio declined as insecticide concentration increased and the survival of both sexes was reduced.
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Edmunds et al. (1985) studied this question.