A lycaenid, Zizina emelina, is distributed in Honshu, Shikoku and Kyushu in Japan. This species is listed in the Red Data List of Japan as one of the most endangered species and chosen as a model insect for the ex-situ conservation project of the Ministry of Environment, Japan. However, we could not succeed in the successive breeding because of difficulty in mating under artificial conditions. In order to clarify the key stimuli to female finding in the male mating behavior, we observed the response of flying male to various wing models in the field. We also observed the behavior of a sympatric lycaenid, Pseudozizeeria maha, whose wing pattern is similar to that of Z. emelina. We used pined male and female specimens of both species with wings open (uppersurface model) and closed (undersurface model). As a result, Z. emelina males frequently approached, contacted and tried to copulate with the conspecific male and female undersurface models, while they scarcely approached the P. maha models. On the other hand, P. maha males approached, made a courtship display to and contacted male and female undersurface models of both species, and they tried to copulate only with the conspecific female undersurface model. Thus the results show that stimuli to finding the conspecific female were different between the two species.