Homozygotes die during the early pupal stage. The larvae form puparia without contraction, remaining long and slender after pupariation. Third larval instar wing discs are flimsy and morphologically abnormal. The larval CNS appears normal. lig^P1/lig^PP1 male escapers show low locomotor activity compared to wild type in the absence of females, but court wild-type females as vigorously as wild-type males do. The mutant males are as active as wild-type males in performing the early steps of mating behaviour (chasing, tapping, singing and licking). After these steps, 73% of the lig^P1/lig^PP1 males attempt copulation with wild-type females, but only 24% of these succeed in copulation. lig^R4/lig^PP1 males mate at normal wild-type rates.