Weakest non-temperature-sensitive allele known. Wing has reasonably good wing blade development, with missing triple-row elements and posterior wing margin. Haltere less well developed but more so than ap⁴. Adults long lived and fertile. Less dominant in heteroallelic combination with ap⁴-like alleles than is ap^56f. ap^77f/Df(2R)M41A4 has more severe phenotype than ap^77f homozygotes.