Variable transformation of A1 to A3. The posterior compartment of A1 and a zone at the anterior margin of A1 are rarely affected. In those cases where they are affected, it is not clear whether they are transformed or deleted. At a low frequency, the following transformations are seen: posterior haltere (T3 structure) to posterior wing (T2 structure), A3 to A5, and A4 to A5. No segmental transformations seen in the embryo. Segmental defects are seen in the abdominal cuticle of adult heterozygotes, with a preference for malformations in even-numbered segments. Defects are most frequent in A4. Defect frequencies are higher in homozygotes of ftzUal2 and heteroallelic combinations of ftzUal1, ftzUal2 and ftzUal3. Defects are also frequently seen in the posterior region of T2 and the anterior region of T3 in adults. Segmental defects are also seen in embryos, with the highest defect frequency in T1, T3, A2, A4, A6 and A8. The A1 transformation phenotype is affected by mutations of Kr, Pc and hb.