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Lateral view of a Male Baetis (Baetidae) (Blue-Winged Olive) Mayfly Dun from Mystery Creek #43 in New York
Blue-winged Olives

Tiny Baetis mayflies are perhaps the most commonly encountered and imitated by anglers on all American trout streams due to their great abundance, widespread distribution, and trout-friendly emergence habits.

Dorsal view of a Setvena wahkeena (Perlodidae) (Wahkeena Springfly) Stonefly Nymph from Mystery Creek #199 in Washington
As far as I can tell, this species has only previously been reported from one site in Oregon along the Columbia gorge. However, the key characteristics are fairly unmistakable in all except for one minor detail:
— 4 small yellow spots on frons visible in photos
— Narrow occipital spinule row curves forward (but doesn’t quite meet on stem of ecdysial suture, as it's supposed to in this species)
— Short spinules on anterior margin of front legs
— Short rposterior row of blunt spinules on abdominal tergae, rather than elongated spinules dorsally
I caught several of these mature nymphs in the fishless, tiny headwaters of a creek high in the Wenatchee Mountains.
27" brown trout, my largest ever. It was the sub-dominant fish in its pool. After this, I hooked the bigger one, but I couldn't land it.
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Mayfly Species Callibaetis pretiosus (Speckled Duns)

This uncommon species may be locally abundant.

Where & when

In 9 records from GBIF, adults of this species have been collected during August (44%), May (22%), July (22%), and September (11%).

In 2 records from GBIF, this species has been collected at elevations of 20 and 72 ft.

Species Range

Physical description

Most physical descriptions on Troutnut are direct or slightly edited quotes from the original scientific sources describing or updating the species, although there may be errors in copying them to this website. Such descriptions aren't always definitive, because species often turn out to be more variable than the original describers observed. In some cases, only a single specimen was described! However, they are useful starting points.

Female Spinner

Body length: ? mm
Wing length: 6.5 mm

A brown species; cross veins of fore wing rather numerous; marginal intercalaries occur singly; male not known.

Body of female brown. Two narrow white stripes on the thoracic notum. Legs pale, tips of tibiae dark, also the tarsal joints. Wings hyaline; veins and cross veins mostly white, but the longitudinal veins with some dark marks. Costal vitta consists of a “fairly broad brown stripe from base to tip, its hind margin sinuate with four projections, four hyaline spots in the subcostal area before the middle, about five pale spots on costal margin before the middle, and several more or less connected beyond.” Along the hind margin are five or six faint irregular clouds. Hind wing much as in Callibaetis floridanus. Abdomen brown, with darker spots on the sides.

Start a Discussion of Callibaetis pretiosus


Mayfly Species Callibaetis pretiosus (Speckled Duns)

Species Range
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