Blue-winged Olive flies
Artificial fly
Blue-winged Olive Quill
Type	Dry fly, Nymph, Emerger
Imitates	Mayflies
Materials
Typical sizes	12-22 standard dry fly, nymph
Uses
Primary use	Trout

Blue-winged Olive flies is a collective term used by anglers in fly fishing to identify a broad array of mayflies having olive, olive-brown bodies and bluish wings in their adult form. Sometimes referred to as BWO, a wide array of artificial flies are tied to imitate adult, nymphal and emerging stages of the aquatic insect. While the family Baetidae probably has the most species identified as blue-winged olives, another mayfly family Ephemerellidae also contains some.^[1] Collectively, blue-winged olive mayflies are an important food source in most trout streams, thus their widespread imitation by fly tiers.

History

The first mention of Blue-winged Olive as common name may be in Frederick Halford's Dry Fly Entomology (1897).^[2] Halford's Blue-winged Olives were identified as members of the genus Ephemerella. Both Alfred Ronald's Fly-Fisher's Entomology (1837)^[3] and Mary Orvis Marbury's Favorite Flies and Their Histories (1892)^[4] do not refer to any flies as Blue-winged Olives. There is ample evidence in fly fishing literature that what are now called Blue-winged Olives were once called Olive Duns, Blue Duns, Iron-blue Duns, Olive Quills, etc.

General description

Swisher and Richards' Selective Trout (1971) gives the following description:^[5]

For the fly-fisherman, it will be much more practical to cover the numerous Blue-wing Olives as one group. In general this group can be divided into two fairly distinct color types. This holds true not only for duns but also for nymphs and spinners. Most duns fall into either the light-gray wing--olive body or medium gray-olive brown body classification. Nymphs are generally brown or olive brown, while spinners are medium or dark brown.

— Doug Swisher and Carl Richards^[5]

List of Blue-winged Olive patterns

Adult patterns

Duns

Spinners