weak wing phenotype - veins L3 and L4 fused only proximally; weak viability phenotype - ratio of the number of fused flies to wild type in fu/+ X fu/Y is 0.75-1.0; intermediate fecundity phenotype - ratio of eggs laid by fu/fu versus fu/+ sisters is 0.25-0.5; weak maternal effect on segmentation - percent of embryos with all segments entirely duplicated is 0-25%.