In adult males, modulates sexual behavior by playing a role in sex discrimination and maintaining normal levels of sexual activity towards both males and females. Expressed in the third antennal segment and the maxillary palp, with increased expression near the cuticle of both olfactory organs (PubMed:10747058). Also detected in the second antenna segment (PubMed:10747058). In the brain, expressed in the central nervous system, with high levels of expression in the visual system including the retina and optic lobe, and uniform expression in the cortex (PubMed:10747058). Detected in the thorax and abdomen, with increased expression in the ventral ganglion (PubMed:10747058). In males, detected in the reproductive tract including the ejaculatory bulb and testis (PubMed:10747058). Detected in embryos, adult males and females. Adult males appear unable to discriminate between males and females when choosing a mate; either because they display increased levels of courtship behavior towards males (when presented with only males) or they display the same levels of courtship towards both males and females (when presented with both sexes) (PubMed:10747058, PubMed:22292044). During male-female courtship, they also begin courting virgin females earlier than wild-type males, suggesting that their increased tendency to court both sexes may also be due to an increase in male sexual activity (PubMed:10747058). No effect on female sexual behavior, and other aspects of male sexual behavior appear unaffected (PubMed:10747058). RNAi-mediated knockdown in neurons of adult males abolishes their ability to discriminate between male and female during courtship (PubMed:22292044). RNAi-mediated knockdown in the mushroom bodies of adult males, results in a slight, but not significant, decrease in their ability to discriminate between males and females (PubMed:22292044). Howver, RNAi-mediated knockdown in various chemosensory peripheral neurons have no effect on male sex discrimination (PubMed:22292044). The name 'quick-to-court' derives from mutant males being quick to initiate courtship of both females and males. Extended N-terminus. Extended N-terminus. Extended N-terminus. Extended N-terminus.