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Mayfly Species Baetis tricaudatus (Blue-Winged Olive)

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Eastern anglers used to know these important mayflies by the storied name of Baetis vagans. The much larger and late Fall hatching Baetis tricaudatus is considered an important Western species with its own tradition, but entomologists recently determined that they are both in fact the same species. The scientific conventions guiding entomologists do not account for a name's regional fame among fishermen, and new or obscure species names may replace their old favorites. Sometimes taxa with disparate traditions are combined. Baetis vagans is one such casualty.

Fortunately, trout think like Shakespeare: A rose by any other name would smell as sweet. The rose that was vagans has lost none of its charm.  

Where & When


Regions: East, Midwest, West

Time Of Year (?): Three broods: Late March to April, late June, and September

Altitude: Any elevation, including high-altitude Western creeks
Eastern anglers are likely to encounter Baetis tricaudatus each season. Good streams produce three broods with distinct peaks, but each may last long enough to overlap with the next, meaning that this mayfly can be found at almost any time of the season. Out West, tricaudatus is the largest of the "Baetis" group with specimens often reaching as large as size 14 (9 mm). Their hatches tend to be heaviest at the "bookends" of the season. Together with the similar appearing but smaller Diphetor hageni (prev. B. parvus), they make up the principal superhatches of Western Olive and Iron Quills.

Hatching Behavior


Time Of Day (?): Warmest part of the afternoon (at least for the early brood)

Habitat: Slow water

Water Temperature: 40°F and up
Soft overcast days with intermittent drizzle can stimulate some of the finest hatch activity of the season. This species exhibits the baetid trait of hatching in "waves" intermixed with spinner falls. This has significant impact on the success or failure of angling methods or flies employed, and the astute angler should take note because the fish sure do. As the hatch begins with the first wave, the majority of the drift will be made up of nymphs followed by emergers with duns finishing as the most numerous form. During the short lull that follows (which can last a few minutes or as long as an hour or more), a spinner fall may occur. Then the cycle repeats itself. Under the right conditions this may happen a half-dozen times or more.

Spinner Behavior


Time Of Day: Variable

Habitat: Same habitat as the emergence
Many baetids, including tricaudatus share the curious trait of landing on objects jutting out of the water and crawling down to deposit their eggs submerged. Even more curious is that the males have been reported to engage in the same behavior. One of their favorite locales is often the legs of stationary wading anglers. There is some evidence of their swimming ability as well. Gravid females and males can also be observed floating placidly on the water at times, especially in sections where weeds just barely meet the surface, perhaps to float up against their hard to see tips for crawling down to oviposit.

Nymph Biology


Current Speed: Any

Substrate: Gravel, vegetation

These nymphs are very active swimmers and are a substantial part of the benthic drift at almost any time of the year.

Pictures of 3 Mayfly Specimens in the Species Baetis tricaudatus:

Female Baetis tricaudatus (Blue-Winged Olive) Mayfly DunFemale Baetis tricaudatus (Blue-Winged Olive) Mayfly Dun View 7 PicturesThis female was associated with a male of the same species.
Collected April 3, 2007 from Owasco Inlet in New York
Added to Troutnut.com by Troutnut on April 3, 2007
Male Baetis tricaudatus (Blue-Winged Olive) Mayfly DunMale Baetis tricaudatus (Blue-Winged Olive) Mayfly Dun View 8 PicturesThis male was associated with a female of the same species.
Collected April 3, 2007 from Owasco Inlet in New York
Added to Troutnut.com by Troutnut on April 3, 2007
Male Baetis tricaudatus (Blue-Winged Olive) Mayfly SpinnerMale Baetis tricaudatus (Blue-Winged Olive) Mayfly Spinner View 1 Pictures
Collected April 15, 2010 from the Flathead River-Lower in Montana
Added to Troutnut.com by Bnewell on June 27, 2011

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