Baëtis rhodani - Large Dark Olive

The large dark olive is found in all kinds of running water, including chalk streams and spate rivers. The nymphs are agile darters.

The dun

The large dark olive dun - a female is pictured above - is an important trout fly. The males are slightly darker and have larger eyes.

The first hatches generally appear in February, with a spring peak in March and April. A few flies hatch all through the season, but other insects take on greater importance from May to September. By late autumn a second peak of large dark olive hatches usually occurs, and at that time an imitation of this handsome upwinged dun can be very useful again.

In early spring and late autumn, hatches are generally centred around midday, with fishing at its best for two hours either side of noon.

The spinner

The large dark olive spinner is slightly darker in body than the dun and has clear wings. The female lays her eggs on emergent vegetation of branches beneath the surface; however, egg laying generally occurs too late in the day to provide good dry fly fishing.

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Footnote: Baëtis is often written simply as Baetis (without the accent on the e) but as this is the scientific name given to a genus the capitalised form Baetis is used rather than baetis.

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