Homozygous males produced as many motile sperm as wild-type males and no morphological abnormalities are detected in the sperm at the light microscope level. However, the homozygous males show fertility that is only 1% that of control heterozygotes. wst^kn108/Df(2R)arr-γ2 males show a further reduction in fertility compared to homozygous males.

The copulation duration of homozygous and control males is not significantly different, and the amount of sperm in the uterus, seminal receptacle and spermathecae of females mated to homozygous and control males appears to be equal immediately after copulation. However, at 5 hours after copulation the number of sperm in the seminal receptacle of females mated to homozygous or wst^kn108/Df(2R)arr-γ2 males is significantly lower than the number seen in females mated to control males. By 24 hours after copulation, 92% of the mutant sperm have been lost from the seminal receptacle and by 120 hours, almost no mutant sperm are left (two-thirds of wild-type sperm are still retained at this stage). The drastic loss of mutant sperm from the seminal receptacle appears to be due to a large number of sperm being released for each ovulation event: at 5 hours after copulation the median is 47 sperm/ovulation event and the maximum that has been observed at a single ovulation is 247 sperm. No significant difference is seen in the number of stored sperm in the spermathecae of females mated to homozygous or control males during the first 24 hours after copulation.

Females mated to homozygous or wst^kn108/Df(2R)arr-γ2 males lay the same number of eggs as females mated to control males on the first day after mating, but reduce the number of eggs laid to the level of virgin females by the third day. The total number of eggs laid by females mated to homozygous males during the first 10 days after copulation is 30% lower than the control number and the egg hatch rate is only 1.2%.

Approximately 85% of eggs laid by females mated to homozygous males are inseminated during 1 to 5 hours after copulation. This rate is significantly lower than the 90% insemination rate seen in females mated to control males. At 22 to 24 hours after copulation, the rate of sperm entry decreases considerably (to approximately 50%) in females mated to homozygous males, despite a high rate of sperm release at this time. Females mated to wst^kn108/Df(2R)arr-γ2 males show more severe defects in sperm entry rates, which are: approximately 77% at 1 to 5 hours after copulation and approximately 33% at 22 to 24 hours after copulation. Nuclear divisions are initiated in an extremely low proportion of eggs inseminated by sperm from homozygous or wst^kn108/Df(2R)arr-γ2 males. The eggs that do not initiate mitotic divisions contain three polar body nuclei (often aggregated to form a single group of chromosomes), the haploid female pronucleus and a single needle-shaped nucleus. The needle-shaped nucleus is the sperm nucleus which has failed to undergo nuclear decondensation.