UTILIZATION OF A PHOTOSYSTEM BY DROSOPHILA-MELANOGASTER LARVAE (DIPTERA, DROSOPHILIDAE)

Foraging-stage third-instar larvae from most wild-type (normal) Drosop hila melanogaster stocks are generally repelled by light. To identify factors that affect the larval photoresponse, we elucidated the effect s of age, temperature, and time on the photoresponse of larvae from a wild-type Canton-S stock. In addition, we analyzed the larvae from the LI2 isofemale line, which are unresponsive to light in a photoassay. To determine whether L12 larvae behave abnormally on other behavioral paradigms, in comparison to Canton-S controls, we tested larvae in tas te and olfactory assays and observed them to determine whether they di spersed in a food source. Like Canton-S larvae, L12 larvae and other i sofemale lines whose progenitors were collected from the same natural population are responsive to taste and olfactory stimuli. Moreover, L1 2 larvae disperse in the food source, as do Canton-S larvae tested in the dark. Larvae expressing para(sbl) mutations, which respond normall y to light but nor to chemical stimuli, do not disperse normally in th e food source, suggesting that dispersal may be mediated by perception of chemical cues.