Heterozygotes have normal flight ability at 22^oC, and poor flight ability at 29^oC. Homozygotes are flightless at both temperatures. Homozygotes have a normal wing posture at 22^oC, and 80% have an abnormal wing posture at 29^oC. Temperature shift experiments suggest that the temperature sensitive period for the recessive wing postural phenotype is limited to pupal development. Approximately half of wupA^hdp-101 Mhc⁵ double heterozygotes have an abnormal wing posture. Double heterozygotes with up^int-3, up¹⁰¹ or up^x have greatly reduced flight ability.