The male of the Mexican bean weevil, Zabrotes subfasciatus Boheman, is 2.059 times as susceptible as the female with 95% limits at 4.824 and 1.031 times to the inhibitory effect of metepa on the adult emergence. The response rate P as the result of cross fertilization between a treated female and treated male was possible to presume by a mathematical model of the independent joint action with a correlation r = 0. P = P_♀+ P_♂(1-P_♀). Here, P_♀ and P_♂ are the response rates produced from the same amount of metepa used in mating treated female×untreated male and untreated female×treated male, respectively.