R. semicolorata is an is in Europe widely spread and its hatches are important for the fly angler.

During May and June I often come across hatches and its spinner fall at dusk has often gave nice trouts on spent imitations.

It is a medium size mayfly with a body of 10-12 mm.

In spite of the english name (yellow upright) its habitus as spinner is more rusty orange to me.

Genitalia detail, ventral view: R.semicolora typical penis lobus