Selected lines of Aedes aegypti with persistently distorted sex ratios

A breeding scheme to isolate X chromosomes sensitive to drive by the T8 (Trinidad) Y chromosome of Aedes aegypti (the MD haplotype) is reported. Crosses with an Australian strain Th.I (Thursday Island) revealed not only sensitive and resistant X chromosomes but also some with the capacity to drive against the T8 Y chromosome. Four strains were created in which sex ratio was male-distorted (28-36 per cent female) for 10 generations, with no regression towards sexual parity. The proportion of females varied significantly between generations in each of the four strains. Further selection produced strains with normal sex ratios, capable of generating fewer than 15 per cent female on outcrossing to T8 males.