13.6% of heterozygous adults show at least one transformation phenotype. trx^JY21/hypomorph (trx^M17, trx^Z32, trx¹, trx^Z16, trx^Z11 or trx^M18) flies show phenotypes that suggest decreased Scr function (transformation of T1 structures to a T2 identity), decreased Ubx function (transformation of T3 to T2), decreased abd-A function (transformation of A2-A7 to A1) and decreased Abd-B function (transformation of posterior abdominal segments to more anterior abdominal identities). These genotypes show higher penetrance and expressivity than these hypomorphs as hemizygotes, suggesting that trx^JY21 may be slightly antimorphic. These genotypes also produce larger transformed patches than the hypomorphs as hemizygotes, sometimes encompassing entire structures. For example:- Transformations in trx^JY21/trx^Z16 flies include, haltere to wing, metathoracic laterotergite to scutum, the development of T3 sternopleural bristles, mesothoracic tibial preapical bristles or mesothoracic tibial apical bristles on the metathoracic tibia, the pigmentation of abdominal tergites 5 to 6 in males, enlargement of abdominal tergite 7 and the transformation of male genitalia to leg. They also exhibit incomplete dorsal fusion of tergites, abnormal abdominal spiracles and abnormal sternites. trx^M18/trx^JY21 pharate adults sometimes develop small heads.