Pharate pupae and the few eclosing adults show a short leg phenotype. Leg length = 30% wild type. Tarsal joints are lacking. Legs are non-functional. The proximodistal order of segments is not grossly affected as landmarks for the coxa, femur, tibia, and first and last (5th) tarsal segments (sex comb and claws, respectively) are present in the correct order. Rows of misoriented sensory bristles indicate that proximodistal polarity is locally perturbed. The stunted legs show no nervous activity except for a faint twitching of the claws and of cuticle over the femur-tibia junction. Allele has a null phenotype when hemizygous but weak or moderate dominant effect when paired with wild type or hypomorphic alleles. The proboscis is reduced in length and width. Null mutants show a substantial reduction in length and width of the labellum and number of pseudo tracheal rows. The prestomal cavity is present and newly eclosed adults can drink. Clypeus, maxillary palps and antennae are apparently normal but there is increased spacing between antennae. Legs of AP-2¹³/+ are slightly shorter than those of AP-2^-/+. When transherozygous with hypomorphic alleles there is a significant reduction in leg length as compared to that of the hypomorphic allele alone.