The tibia of this Isonychia bicolor mayfly spinner is highlighted in red.
Tibia: A middle segments in the leg of an insect, located between the femur and the tarsus.) and a thin but distinct dorsal (Dorsal: Top.) stripe faded in the center which looks very different from the stripes on Ephemerella needhami and Ephemerella aurivillii. It definitely has the fan tail characteristic of the Ephemerella genus.