A role for the Pax-6 homologue eyeless in adult Drosophila brain development and 
function is described. eyeless expression is detected in neurons, but not glial 
cells, of the mushroom bodies, the medullar cortex, the lateral horn, and the 
pars intercerebralis. Furthermore, severe defects in adult brain structures 
essential for vision, olfaction, and for the coordination of locomotion are 
provoked by two newly isolated mutations of Pax-6/eyeless that result in 
truncated proteins. Consistent with the morphological lesions, we observe 
defective walking behavior for these eyeless mutants. The implications of these 
data for understanding postembryonic brain development and function in 
Drosophila are discussed.