Mutants have a hypoplasia in the primary visual neuropil. This hypoplasia compared to wild-type is largest for the lobula plate (about 39%) and smallest for then lobula (about 14%). The central brain seems to be generally larger than in wild-type (ellipsoid body appears to be about 15% larger) The protocerebral bridge is about 19% smaller than wild-type, The handlebar shaped rod is about the same length, but is thinner than wild-type. The distance between the lobula and the lobula plate is about 3-5% smaller than in wild-type.

Reduction in fibre number in the anterior optic tracts.

Testing rol¹, sol¹ double mutant's visually mediated course control during tethered flight lead to the conclusion that visual orientation is an operant behavior.

Relatively proximal portion of optic lobes, except for lamina, reduced in volume to approximately 40-50% normal; less severe reduction than in sol¹; rol¹ sol¹ double mutant has extremely small visual system (connecting eye to central brain), whose volume is some 12% of normal and whose lobula plate optic ganglion is absent. Behavioral experiments reported for rol¹ sol¹ (a single mutant involving only the former exhibits only subtle defects in visual behavior). The double mutant is blind in terms of standard optomotor responses to rotating vertical stripes, but it can respond to the positions of landmarks by making turning maneuvers. These optic-lobe-depleted flies can make use of the magnitudes, though not the directions, of moving patterns to stabilize the panorama presented to them; they do so apparently by sampling the optomotor torque value which has the effect of putting them in optomotor balance; thus, it is concluded that the double mutant's visual orientation is an operant behavior.

mnb¹, rol¹, sol¹ has abnormal neurophysiology phenotype

rol¹, sol¹ has abnormal neuroanatomy phenotype

rol¹, sol¹ has abnormal optomotor response phenotype