Wings and halteres reduced to traces. Bristles eliminated from area around wing base (including posterior notopleurals, anterior and posterior supra-alars, and anterior postalars); posterior scutellars erect when present but missing in first counts; dorsocentrals smaller and fewer; hairs on thorax sparse and irregular. Sutural furrow reduced; thorax disproportionately small. Flies small, pale, weak, and very short lived. Viability about 70% that of wild type, but erratic. RK2.

ap¹ has phenotype, non-suppressible by su(Hw)²