The X-linked temperature-sensitive recessive mutant of Drosophila, shibirets1(shits1) paralyzes at 30。C during pupal development in shits1 flies induce abnormal epidermis without any macrochaete bristles. We examined temperature-sensitive defects in the development of mechanosensory bristles on the head and thoraces of shits1 flies uon exposure to a brief heat-pulse at various times during pupal development. White prepupae were collected and raised at 17。C and vials of pupae were exposed to 30。C for 4hrs at successive 4-hr intervals throughout puparium stage. All the macrochaetae on the head and thoraces were examined after eclosion. We found that all the bristles of shits1 flies have a specific temperature-sensitive period (TSP) during development. Heat pulses during TSP caused a failure of normal bristle development in shits1 flies. Specifically, bristles in the head and notum were affected by high temperature during 28-64 hr after puparium formation(apf). Interestingly, the effects were greatly reduced in most macrochaetae over 52hr apf and no effect was found after 68hr apf the role of shits1 gene on mechanosensory bristle development was examined by β-galactosidase activity labeled sensilla. Results indicate that 4-hr heat pulse between 28-64 hr apf specifically inhibited the differentiation of tormogen and trichogen. Since the macrochaete and the accompanying sensory cells are derived from a common precursor cell, these results suggest a developmental time window in which each bristle and their sensory cells differentiate.