Tpi^wstd-1 homozygotes exhibit essentially normal locomotor activity. However, when shifted abruptly to 38[o]C, the mutants lose motor control and fall to the bottom of the vial within 1 minute, with occasional spasmodic activity and leg twitching. Paralysis becomes complete within 3-5 minutes at the elevated temperature. In contrast, wild-type and Tpi^wstd-1/+ flies remain active at 38[o]C for >30 minutes. Paralytic behaviour of Tpi^wstd-1 homozygotes at 38[o]C varies as a function of age. Within the first day after eclosion, only approximately 10% of mutant adults are paralyzed after a 2 minute exposure to 38[o]C. This fraction increases to >90% for 6-day old flies. The time required for 100% of the flies to become paralysed decreases from >10 minutes for 1-day old Tpi^wstd-1 flies to 4 minutes for 7-day old flies to approximately 1 minute for 14-day old flies. Kinetics of recovery from paralysis show the converse age dependence. After a 10 minute exposure to 38[o]C, approximately 50% of flies that are <1 day posteclosion recover the ability to stand almost immediately upon a return to room temperature. This time increases to >3.3 minutes for 2-day old flies and 7.4 minutes for 6-day old flies. After 3 weeks of age, Tpi^wstd-1 flies require upwards of 30 minutes to recover from paralysis. Tpi^wstd-1 mutants are short-lived compared to wild-type controls, with the difference in lifespan accentuated at elevated temperatures. At 22[o]C, Tpi^wstd-1 flies reach the midpoint of their survival curve (lifespan is 41.4 days, compared with 54 days for controls). At 29[o]C, the lifespan of Tpi^wstd-1 flies is dramatically reduced to only 4 days, approximately 10 times less than for control flies at this temperature.