The family Baetidae is known to be the most species-rich family in the order Ephemeroptera. The genus Baetis contains up to 160 species, but members of the genus in East Asia are still poorly investigated. In this paper, Baetis spinoculis sp. nov., is described based on larval specimens collected in a stream of the Chiaksan mountain in Korea. While four species in the genus have been described in Korea: Baetis fuscatus (Linnaeus), B. silvaticus Kluge, B. pseudothermicus Kluge, and B. ursinus Kazlauskas, this new species is distinguished from other Korean baetid species by both genetic and morphological characteristics. B. spinoculis can be separated from the related B. pseudothermicus group by the COI genetic distant. The cuticle structures on paraproct plates and abdominal pigment patterns also distinguish B. spinoculis from B. pseudothermicus and other related species.

• Wooseong Kim(Department of Environmental Science and Ecological Engineering, Graduate School, Korea university, Republic of Korea)
• Yeon Jae Bae(Department of Environmental Science and Ecological Engineering, Graduate School, Korea university, Republic of Korea)