78% of homozygous males do not court wild-type virgin females at all and 17% perform only some of the courtship steps. Most of the mutant males that do court (13%) perform only early steps of courtship (orienting, following and wing extension). Only 5% of homozygous males eventually copulate, and these matings give no progeny. The courtship index (C.I.) representing the fraction of the observation time spent courting is 12% for homozygous males, compared to 72% for wild-type males (breaking down this value for courting and noncourting mutant males gives a C.I. value of 0 and 23% respectively). Homozygous females are fertile when mated to wild-type males, behave normally and are as receptive to males as are wild-type females. Homozygous flies are attracted to light to the same extent as wild-type flies. No gross defect in the olfactory response of homozygous males is seen in response to the olfactory attractants Drosophila culture medium and wild-type virgin females. Locomotor activity of homozygous flies is normal. The 4 mitotic divisions of the primary spermatogonial cells occur normally in homozygous males, and cysts containing 16 primary spermatocytes are seen. However, the two consecutive meiotic divisions do not take place and no cysts with 32 or 64 haploid spermatids are seen. The primary spermatocytes undergo an immediate transition to elongated spermatids that have rather long tails and heads that are larger in size and different in shape than those of normal spermatids. The bundles of spermatids are not as well organised as in wild-type males.

Very early steps of courtship behavior are disrupted. Spermatogenesis is abnormal.