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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
Baetis

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 Grammotaulius betteni (Limnephilidae) (Northern Caddisfly) Caddisfly Larva from the Yakima River in Washington
This is a striking caddis larva with an interesting color pattern on the head. Here are some characteristics I was able to see under the microscope, but could not easily expose for a picture:
- The prosternal horn is present.
- The mandible is clearly toothed, not formed into a uniform scraper blade.
- The seems to be only 2 major setae on the ventral edge of the hind femur.
- Chloride epithelia seem to be absent from the dorsal side of any abdominal segments.
Based on these characteristics and the ones more easily visible from the pictures, this seems to be Grammotaulius. The key's description of the case is spot-on: "Case cylindrical, made of longitudinally arranged sedge or similar leaves," as is the description of the markings on the head, "Dorsum of head light brownish yellow with numerous discrete, small, dark spots." The spot pattern on the head is a very good match to figure 19.312 of Merritt R.W., Cummins, K.W., and Berg, M.B. (2019). The species ID is based on Grammotaulius betteni being the only species of this genus known in Washington state.
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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Troutnut
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Bellevue, WA

Posts: 2758
Troutnut on Jul 22, 2006July 22nd, 2006, 6:13 am EDT
It's fairly common knowledge that many Baetis mayflies crawl underwater to lay their eggs. What's strange is that most authors don't seem very surprised by this. As best I can tell from all my recent reading and note-taking, Baetis is the only genus of mayflies which displays this behavior. That seems remarkable.

Does anybody know of any other mayflies that do this? Have I missed something?
Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist
Taxon
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Site Editor
Plano, TX

Posts: 1311
Taxon on Jul 22, 2006July 22nd, 2006, 10:00 am EDT
Jason-

As far as I know, Baetis is the only mayfly genus reported to display that oviposition behavior.
Best regards,
Roger Rohrbeck
www.FlyfishingEntomology.com

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