The recessive mutant, called "deep orange" because of its effect on eye color, is located at 0.0[plus or minus] on the X chromosome. The effect on fertility is similar to that of fused, in that homozygous females deposit eggs which fail to hatch if fertilized by deep orange males, but produce a few heterozygous females if fertilized by wild type males. All eggs from the heterozygous females fertilized by deep orange males develop normally. Development seems to hinge on the presence of the wild type gene at some stage. This gene can exert its effect prior to meiosis and be absent from the genotype or it can be introduced in the sperm at fertilization and still cause normal development.