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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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Posts: 24
Isidro on Mar 26, 2008March 26th, 2008, 2:39 am EDT
This one is very common into my city and could be the adult of the nymph showed in the last thread. It's a big one, about 20 mm. wingspan. Two cerci, very big eyes and very conspicuous dark venation. Could be Ecdyonurus cf. venosus?

This one is about to becomes a ctrab spider lunch.

Zaragoza, NE Spain.

Many thanks,

Taxon's profile picture
Site Editor
Plano, TX

Posts: 1311
Taxon on Mar 26, 2008March 26th, 2008, 6:15 am EDT

Yes, Ecdyonurus venosus, however I suspect the body length (not including tails) may be more like 14 mm.
Best regards,
Roger Rohrbeck
Posts: 24
Isidro on Mar 26, 2008March 26th, 2008, 6:54 pm EDT
Wow!!! Many thanks Taxon!! You have identified it at species level! I had doubts because there are more similar species in genus. Yes, the body length, as you said, I thinks is about 15 mm. (without cerci).

Then, I think that the nymph in the last post is from this species, due to any other Ecdyonurus is seen into my city and this one is very common.

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