Retarded development of females, a case of maternal inheritance in a moth, Ephestia kuehniella

Retarded development of females (Symbol: Rf) has arisen spontaneously as a new trait in a chromosome mutant strain, which has an autosome fused to the original W chromosome. Female imagines with this trait emerge 1–3 weeks later than the males, due to retarded larval development. The proportion of female imagines is low. Rf is maternally inherited, it is neither expressed in nor transmitted through males. The evidence suggests that it is a dominant or epistatic factor on the autosomal part of the W chromosome-autosome fusion.