Mutant females exhibit substantial alterations in female behaviour and fertility. retn^z2-428/retn² flies eclose with only 8% of expected rates. retn^z2-428/retn¹ flies eclose with only 25% of expected rates. retn^89.GAL4/retn^z2-428 flies eclose with only 33% of expected rates. Mutant females are strikingly resistant to male courtship. retn^z2-428/retn² females copulate after an average 58+-2 minutes compared to an average of 3 minutes for wild-type. retn^z2-428/retn^RU50 females copulate after an average 8.8+-2 minutes compared to an average of 3 minutes for wild-type. retn^z2-428/retn⁰⁵⁰⁹⁶ females exhibit male like courtship behaviours. Mutant females follow, tap and appear to sing. Although not as robust as male courtship - following is not as sustained, full wing extension and vibration is not seen, and copulatory bending is weak or absent - these behaviours resemble courtship. male-male and male-female courtship in retn^z2-428/retn^RU50 and retn^z2-428/retn⁰⁵⁰⁹⁶ mutant males is comparable to wild-type. retn^89.GAL4/retn^z2-428 animals also exhibit mushroom body (MB) specific abnormalities. MB neurons diverge within the nerve tracks and axons from the posterior part of the β-lobe neurons cross the midline and join with the opposite β-lobe neurons, causing β-lobe fusion. This is more common in females than in males. retn⁰⁵⁰⁹⁶/retn^z2-428 animals also exhibit mushroom body (MB) specific abnormalities. A subset of MB neurons diverge within the nerve tracks and axons from the posterior part of the β-lobe neurons cross the midline and join with the opposite β-lobe neurons, causing β-lobe fusion. This is more common in females than in males.