Opt^G is a homeotic modifier of ey² and possibly other small-eye mutants (e.g., ey^D/+). In the presence of Opt mutations, ey² flies exhibit protrusions of wing tissue from the region of the eye; development is normal at 17^oC, but homeotic transformation is observed at 29^oC; the temperature-sensitive period is during the second larval instar. Protrusions from the anterior portion of the eye have the triple row of bristles characteristic of the anterior wing margin; the fronto-orbital region of the head produces bristles with bracts characteristic of the costa in the proximal wing.