Df(1)os1 mutant flies have outstretched wings and small eyes compared to wild type.
Mutant eyes are small and have about 450 ommatidia, compared to 750 ommatidia in wild-type. The third instar larval eye disc is reduced in size in these mutants. The number of mitotic cells in the first mitotic wave is reduced compared to wild-type.
Mutants have a small eye phenotype.