Rithrogena Semicolorata - Olive Uprights
The olive upright, a close relative of the March Brown, is found on just about every river in Britain, and it is probably the most abundant spring fly of all. The nymphs are flattened stone clingers and are found in all kinds of running water, including chalk streams and spate rivers. The dun hatches throughout the day from May until July. Hatches are often heaviest towards evening, and at that time the spinners also appear, but their egg laying occurs very late in the day so that the duns are usually far more important as far as trout fishers are concerned.