Published online by Cambridge University Press: 10 July 2009
Crosses of Sudanese strains of Anopheles arabiensis Patt. resistant and susceptible to malathion indicated that the resistance was incompletely dominant. The results of tests of male progeny of successive backcrosses agreed well with the hypothesis of control of the resistance by a single gene. However, the results from females suggested the additional involvement of a sex-limited modifier. Tests of mixtures initiated with a 1:1 ratio of resistant and susceptible first-instar larvae gave little evidence for selective mortality during the larval stage. However, the mortalities in tests on malathion recorded among adults emerging on successive days from these mixtures, and also from F2 and backcross progenies, indicated that the development of the resistant larvae was significantly faster than that of the susceptible ones. The fact that this occurred in the F2 and backcross progenies indicates that it may be due to a pleiotropic effect of the resistance gene, but it is pointed out that results from much more prolonged backcrossing would be necessary to rule out the possible effects of linked genes.