Blue-winged Olive flies

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. 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). Halford's Blue-winged Olives were identified as members of the genus Ephemerella. Both Alfred Ronald's Fly-Fisher's Entomology (1837) and Mary Orvis Marbury's Favorite Flies and Their Histories (1892) 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:

"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."

Duns
• As described in Flies for Trout (Stewart and Allen, 1993):

• Classic Blue Dun

• Blue Quill

• Blue Wing Olive

• Blue Wing Olive, Loop Para Dun

• As described in A.K.'s Fly Box, A.K. Best (1996)

• Olive Quill Dun

• Olive Quill Dun Parachute

• As described in Trout Country Flies (Staples, 2002):

• Donnelly Blue Dun

• Sparkle Dun

Spinners
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As described in Flies for Trout: As described in A.K.'s Fly Box, A.K. Best (1996) As described in  Trout Country Flies  (2002), Bruce Staples
 * Blue Wing Olive Crystal Wing Spinner
 * Clear Wing Spinner, Brown
 * NQ Quill Spinner
 * Red Quill Spinner
 * Light Olive Quill Spinner
 * Flatwing Spinner
 * Hen Spinner

Nymph patterns
As described in Flies for Trout: As described in  Trout Country Flies  (2002), Bruce Staples
 * Gold Ribbed Hare's Ear
 * Baetis nymph
 * Pheasant Tail nymph
 * Sparkle PT Nymph

Emerger patterns
As described in Flies for Trout:
 * Captive Dun
 * Compara Emerger
 * Loop Wing Emerger Olive

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