From around May through to August damsels nymphs will be emerging out of the water to hatch in to adult flies. As a large nymph they provide a meaty mouthful for trout who often feed on them enthusiastically. This is a classic fly pattern and a must have trout fly for still water anglers. The life like movement of the Marabou feathers and the realistic eye make these damsel fly nymphs great fish catchers.
It's important to remember that damsels frequent rivers as well and we have have great success using these damsel fly nymphs on rivers too.