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Lateral view of a Female Hexagenia limbata (Ephemeridae) (Hex) Mayfly Dun from the Namekagon River in Wisconsin
Hex Mayflies
Hexagenia limbata

The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large brown trout that only touch streamers for the rest of the year.

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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Kinzua
W. PA

Posts: 20
Kinzua on Feb 7, 2009February 7th, 2009, 1:20 am EST
Does any one know if this mayfly is found outside of New Zealand? In particular, is it found in the streams of Hokkaido Japan?

Thanks in advance,
John
Taxon
Taxon's profile picture
Site Editor
Plano, TX

Posts: 1311
Taxon on Feb 7, 2009February 7th, 2009, 4:01 am EST
John-

I doubt it, but suggest you pose your question to:

Peter M. Grant, Department of Biological Sciences, Southwestern Oklahoma State University, 100 Campus Drive, Weatherford, Oklahoma 73096-3098 USA, phone (580) 774-3294, fax (580) 774-7140, email peter.grant@swosu.edu.
Best regards,
Roger Rohrbeck
www.FlyfishingEntomology.com
Konchu
Konchu's profile picture
Site Editor
Indiana

Posts: 498
Konchu on Feb 7, 2009February 7th, 2009, 10:28 am EST
A checklist of Japanese mayflies can be found on this webpage:
http://www.famu.org/mayfly/mfbib_hi.php.

Scroll down to:
Ishiwata S-I. 2001. A checklist of Japanese Ephemeroptera. Pages 55-84 in Bae YJ (ed.) The 21st Century and Aquatic Entomology in East Asia. Proceedings of the 1st Symposium of Aquatic Entomologists in East Asia. The Korean Society of Aquatic Entomology, Korea.

A PDF file is available for download there.
Taxon
Taxon's profile picture
Site Editor
Plano, TX

Posts: 1311
Taxon on Feb 8, 2009February 8th, 2009, 3:26 am EST
John-

Based on the Checklist of Japanese Mayflies which Konchu located, the only Oligoneuriid found in Japan is Oligoneuriella rhenana, and it is apparently only found on the island of Honshu.
Best regards,
Roger Rohrbeck
www.FlyfishingEntomology.com
Kinzua
W. PA

Posts: 20
Kinzua on Feb 8, 2009February 8th, 2009, 4:23 am EST
Taxon and Konchu,
Thank you for your help! Ephemeroptera Galactica - WOW, what a great resource!

John
Taxon
Taxon's profile picture
Site Editor
Plano, TX

Posts: 1311
Taxon on Feb 10, 2009February 10th, 2009, 11:11 am EST
John-

Japanese Mayfly Distribution should be a bit easier to use than the .pdf in case you should be curious about the distribution of any more Japanese mayfly species.
Best regards,
Roger Rohrbeck
www.FlyfishingEntomology.com
Kinzua
W. PA

Posts: 20
Kinzua on Feb 14, 2009February 14th, 2009, 8:59 am EST
Double WOW! and thanks.

John

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