One of the first flies to show on the river in any numbers and an important food source for both trout and grayling.

All the photographs sen below show both male and female insects at differing times of their life cycle and were recorded on the River Usk between 1960 and 1986.

Its scientific name is Baetis Rhondani. By its initial categorization, of being a baetis it infers that the nymph is an ‘agile darter’ and free swimming as opposed to a stone clinger.

Large Dark Olive Nymph

Large Dark Olive Male Dun

Large Dark Olive Male Dun (from another angle)

Large Dark Olive Female Dun.


Large Dark Olive Female Dun (from another angle)


Large Dark Olive Male Spinner


Large Dark Olive Female Spinner

The main identification of the male from the female are the forceps of the male that are normally just under the base of its tail

The Lard Dark Olive Male Forceps

These forceps can be seen on both the dun and the spinners.