Abstract: By way of orthogonal experiments it was found that under certain temperature and relative humidity the factors limiting male responsiveness of C. variegata were light intensity, male age and method of release of sex pheromone samples, the optimal conditions were l lx., the first day after emergence and the syringe method respectively.The syringe bioassay method is a new one. After dropping the pheromone sample on the end of the plunger, the syringe was heated in the water bath at 100癈 for 3-5 min., and then the air containing the pheromone was pushed gently into a bio-assay flask along its wall. Response of the male moths to the pheromone was recognized by the characteristic wing vibration and abdomen extension. The number of male moths responding for 2 min. was recorded and the percentage of male response was culculated. Tests done by the syringe method indisated that even the amount of the pheromone was as low as Ixl0~6 FE., the percentage of the responding males still reached 17%. Control experiments showed that the method itself did not cause the male to response.A regression equation has been derived under the above mentioned optimal conditions, i.e., y=116.75 +15.52x, where y represents the male response(per cent) and x represents the female equivalent(log).