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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.

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 Rhithrogena virilis

I haven't found any details about this species in the angling literature, although it seems to be relatively widespread and commonly encountered in low numbers on western rivers.

Where & when

Time of year : Spring to early summer

Species Range

Spinner behavior

Time of day: Midday-evening

I have frequently encountered sparse numbers of these mayflies on the rivers around Seattle in June or early July, soon after snow runoff from the mountains ends.

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.

Male Spinner

Body length: 12 mm
Wing length: 15 mm

A large species with the usual almost unicolorous, brown coloration. Head brown with ochreous shading around bases of antennae and the anterior portion suffused with smoky. Notum brown, with the scutellum and adjacent parts light ochre-brown; pleura shaded with ochreous, particularly anterior to base of wings, a dark streak from base of forewing to pronotum; sternum tinged with smoky in median area. Abdomen brown, irregularly paler along lateral edge and on posterior segments ventrally. Forceps and setae deep smoky. Forelegs deep smoky; mid and hind legs lighter brown with the usual smoky streak on each femur. Wings hyaline with a faint tinge of amber along costa; veins and crossveins fine, deep brown, the latter anastomosing as usual in pterostigmatic region.

Female Spinner

Body length: 12 mm
Wing length: 15 mm

Head suffused with smoky anterior to antennae; area between ocelli and antennae light ochreous; next the eyes and posterior to ocelli light ruddy brown with a slight median smoky tinge and the vertex in lateral angles slightly ochreous. Otherwise very similar to male, but with slightly paler thorax.

Specimens of the Mayfly Species Rhithrogena virilis

1 Female Dun
3 Male Spinners
2 Nymphs

Start a Discussion of Rhithrogena virilis


Mayfly Species Rhithrogena virilis

Species Range
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