Genetic distortion of sex ratio in a mosquito Aedes aegypti

CRAIG, HICKEY and VANDEHEY (1960) reported that a hereditary factor transmitted by males was responsible for high male ratios in A. aegypti. This phenomenon was designated as male-producing or MP. Males from high maleproducing families produced a high proportion of males in their own progeny, regardless of the type of female to which they were crossed. This condition was not due to selective mortality, at least in postgametic stages. In 1960, nothing was known about the sex-determining mechanism in A. aegypti. In addition, the male-producing lines available for study were highly variable in expression. These factors hampered more precise analysis of the mechanism of inheritance of MP. The present work was initiated because new crosses with different strains gave more pronounced and predictable distortion of sex ratios. Earlier strains gave about 15 to 30% female, whereas present lines produce about 0 to 15% female. This paper presents an analysis of the mode of inheritance of MP. In addition, data suggesting the mechanism of action are included. Separate reports will be published elsewhere on ( 1 ) the distribution and behavior of MP in experimental populations and (2) the effect of environment on expression of MP. A more detailed account of some of this work is given by HICKEY (1965a, b). Nomenclature used ih these preliminary reports is superseded by that in the present work.