Linkage, expression, and distribution of the pyrethroid resistance gene in the horn fly (Diptera: Muscidae)

A sex-linked gene for pyrethroid resistance in the horn fly, Haematobia irritans (L.), showed complete linkage to the male-determining gene in a laboratory colony that had been inbred for 10 generations. Within susceptible, heterozygous, and resistant populations, the level of resistance that was expressed was greater for females than for males. The increase in level of resistance conferred by the gene was similar for females and males. Preliminary synergism and allelism tests supported our supposition that the same gene was responsible for resistance in California, Florida, and Texas populations.