ABSTRACT
Populations of 1-day-old pupae of Culex pipiens molestus Forsk exposed to substerilizing doses of irradiation [500, 1000, and 2000r] and [500 and 1000r], each generation for as many as 5 and 11 generations respectively, were treated with two additional acute doses of 4000 and 8000r in the 6th and 12th generation. Selected populations [F[6]] exposed to additional acute dose of 4000r showed a slight significant decrease in adult emergence. Previously treated populations [F[12]] with dose of 500 and 1000r showed a slight significant decrease and a slight increase in adult emergence respectively when exposed to additional dose of 4000r, although this slight increase is less than the control. Selected populations [F[6]] and [F[12]] exposed to additional acute dose of 8000r showed a slight significant increase in adult emergence. Additional doses of 4000 and 8000r to [F[6]] and [F[12]] had no significant effect on sex ratio. Radiation selected populations of [F[6]] and [F[12]] exposed to additional acute doses of 4000 and 8000r showed distinct significant increase in the mean survival rate of both males and females than the unirradiated populations. A significant decrease in the reproductive capacity and an increase in sterility were observed among radiation selected populations [F[6]] and [F[12]] females exposed to additional acute dose of 4000r. This decrease is positively correlated with the size of the applied dose and with the number of ancestral generations treated. Complete sterility was observed in the radiation selected populations [F[6]] and [F[12]] when exposed to additional acute dose of 8000r. Therefore exposure of the selected populations to two additional acute doses of 4000 and 8000r revealed no evidence of increased resistance to acute radiation even after eleven generations of selection