The intertidal flat at the mouth of the Yoshino River is well-known as one of few remaining habitatsfor fiddler crabs, Genus Uca, that are classified in the near threatened species in the Red Data List edited by the Environmental Agency of Japan. To understand characteristics of this benthic animal's life history on and around the intertidal flat is useful for examining conservation methods of thearea. In this study, the hatching and dispersion process of the larvae of Genus Uca were investigated through laboratory experiments and field observations. The results are summarized as follows: 1) The larvae of Genus Uca are hatched during a restricted period around a flood tide in a spring tide. 2) The adaptability of zoeae to variations of salinity is considered to be fairly high because they were collected at positions with a wide rangc of salinity. 3) The amount of zoeaindividuals emerging in one hour at this intertidal flat was estimated to be about 150, 000.