Abstract
Continued selection of the spotted root maggot, Euxesta notata (Wiedemann), with dieldrin or with DDT, applied to strains in which dieldrin resistance and DDT resistance had already been developed, resulted in a decrease in these resistances. Determinations of the genotype composition of successive generations indicated this to be due to the disappearance first of the RR homozygotes and ultimately of the rr homozygotes, resulting in the strains consisting entirely of dieldrin-resistant or DDT-resistant heterozygotes produced from heterozygotes. This fact was confirmed by determinations of percentage hatch of eggs, where the lethality operated. It is concluded that the factors for dieldrin resistance and for DDT resistance are probably on separate chromosomes and that 2 distinct balanced lethal systems were evolved by the prolonged selection with these insecticides.
Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
