Antenna transformed into second leg plus some differentiation toward a first leg but with recognizable arista usually present; not like ssa, in which main effect is that the arista becomes tarsuslike. Enhanced by Pc1. Enhanced by Pc2. Pc/AntpYu has a pair of excellent antennal legs complete with tarsae and with sex combs in the male. RK3A.
Yu, 1948.
Strong dominant allele.