Three species of a genus Tenuibaetis (Ephemeroptera: Baetidae) from Japan, with description of a new species

We associated nymphs of three Tenuibaetis species with their imagoes by rearing. Herein we redescribe T. flexifemora and T. pseudofrequentus, and also provide description of a new species T. parvipterus. Tenuibaetis pseudofrequentus is morphologically similar to T. flexifemora in the imaginal stage, but we can distinguish these two species by the color patterns of their nymphs and their geographical distribution. Tenuibaetis parvipterus is distinguishable from the other two species by the fore femur, which is not bending distinctly, and abdominal sterna without distinct spots of male imago, reduced hind wing and abdominal sterna without distinct spots of female imago, and difference in color patterns of the abdomen of nymphs. Diagnostic characters of these species were tabulated.