Expression of Abd-B^r.hs using heat shock during the late cellular blastoderm stage usually results in the failure of germ band retraction. Abdominal denticle belts are reduced in size, approaching the shape of thoracic denticle belts, although the denticle hairs remain abdominal in character. The first thoracic denticle belt is narrower than wild-type and the T1 beard is reduced or missing. The denticles of the second and third thoracic segments are wider and thicker than normal, appearing abdominal in character. In some cases complete denticle belts do not form ventrally, and patches of abdominal type denticle hairs are seen in ventro-lateral positions of the thoracic and abdominal segments. Ventral pits are often seen in abdominal segments. Rudimentary filzkorper and/or perispiracular hairs are occasionally seen in the most posterior abdominal segments, and rarely as far anteriorly as thoracic segments. Head involution is severely inhibited and denticle belts are often seen in the cephalic segments, sometimes forming belts. Tubular structures resembling fragments of the posterior tracheal system appear reiterated in anterior segments. Expression of Abd-B^r.hs using heat shock during the first 24 hours of the third larval instar stage often results in transformation of distal antennal structures into distal leg structures. The arista is transformed into tarsal leg and tarsal claws occasionally develop in the distalmost regions of the transformed leg tissue. Part of the third antennal segment is sometimes transformed towards more proximal leg tissue, producing leg bristles. Many of these animals do not eclose from the pupal case. Expression of Abd-B^r.hs using heat shock for 30 minutes during the second day of the third larval instar stage results in late larval or early pupal lethality in most cases.