Abstract
Mesomermis japonicus n. sp. is described from larvae of Simulium japonicum collected in the Yataro River of the Kanagawa Prefecture in Japan. It can be distinguished from previously described Mesomermis species by the shape and size of the amphids and the character of the spicules and vagina. At 15℃, the postparasitic juveniles molted between 9 and 23 days after emergence, began ovipositing 6-23 days later and hatching occurred 34-41 days after oviposition. Females produced between 556 and 2936 eggs during their life time.
