Homozygous larvae are negatively photokinetic with a stimulus indice significantly higher than wild type control. Heterozygotes have an indice similar to wild type, transheterozygotes with lphA¹ have a higher indice and transheterozygotes with rdgA¹ or oc¹ have a lower indice. Transheterozygotes with Df(1)C52 have an extremely high indice and are blind. Homozygotes respond normally to light in a phototaxis assay, ERG is normal, males perform vigorous courtship in response to wild type females and perform the behaviour 'orientation', rarely performed by blind or visually impaired males. Hemizygotes are blind. Mutation does not affect larval responses to olfactory or taste stimuli.