A GENETICAL STUDY OF DDT-RESISTANCE IN THE TRINIDAD STRAIN OF AEDES AEGYPTI L.

Previous genetical investigations on the Trinidad DDT-resistant strain of Aedes aegypti, involving mass crosses with susceptible strains, had indicated that a single major semi-dominant gene controlled resistance to DDT. The present study, in which single-pair matings were made, indicates that the genetic control of resistance is, in fact, more complex. The considerable variation observed could not be interpreted in terms of normal segregation at a single locus. At least three genetic factors appear to be involved: a major gene conferring low resistance but of variable expression, a chromosomal modifier of the dominance of this first factor, and a sex-dependent factor that may or may not be chromosomal. Whether the major gene for low resistance, variously modified, is also responsible for higher levels of resistance remains uncertain.