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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.

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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Millcreek has attached these 7 pictures. The message is below.
Collected September 19, 2010. Mature larvae with cases. Cases left to right; 29 mm, 26 mm and 20 mm. Larvae from left to right; 21 mm, 19 mm and 17 mm. In alcohol.
Collected September 19, 2010. Mature larva. 21 mm. In alcohol.
Collected September 19, 2010. Mature larva. 21 mm. In alcohol.
Collected September 19, 2010. Mature larva. 21 mm. In alcohol.
Collected August 17, 2009. Immature larva. 8 mm. In alcohol.
Collected August 17, 2009. Immature larvae and cases. Cases 8 - 14 mm. Larvae 6 -8 mm. In alcohol.
Nerophilus californicus cases used by Heteroplectron californicum larvae. Heteroplectron larva in photo was using the case on it's left.
Millcreek
Healdsburg, CA

Posts: 344
Millcreek on Sep 28, 2014September 28th, 2014, 9:07 pm EDT
These larvae are common in Mill Creek (a tributary to Dry Creek which empties into the Russian River). The larvae were keyed to genus using "Larvae of the North American Caddisfly Genera (Trichoptera)" by Wiggins (1996) and with Merritt, Cummins and Berg (2008). There are only two known species of Heteroplectron in North America, H. californicum and H. americanum. H. californicum is found only on the west coast and H. americanum only on the east coast.

Mature larvae bore a hole through a piece of water-logged wood and use it as a case. The inside of the case is lined with silk and the posterior end is plugged with a small stone or piece of vegetation held in place with silk. Smaller larvae make a somewhat ramshackle case of bits of wood with Douglas fir or redwood needles attached to it. Both methods make very effective camouflage. I only noticed them at first when I was looking for other stream critters and noticed a piece of wood heading upstream on the streambed.

Some mature larvae will appropriate another caddis case for use. The last photo shows a Heteroplectron californicum larva that was collected while using the case of Nerophilus californicus. I initially thought that the case on the left was a spent pupal case of N. californicus but Wiggins (1996) says that H. californicum often attaches small pieces of wood to the anterior edge of cases it appropriates. Nerophilus californicus does not use these small pieces of wood in it's case construction.

H. californicum larvae are usually found in slow water on the edges of pools and glides.
"If we knew what it was we were doing, it would not be called research, would it?"
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Taxon
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Site Editor
Plano, TX

Posts: 1311
Taxon on Sep 28, 2014September 28th, 2014, 9:36 pm EDT
Very cool, Mark !!!
Best regards,
Roger Rohrbeck
www.FlyfishingEntomology.com
Millcreek
Healdsburg, CA

Posts: 344
Millcreek on Sep 28, 2014September 28th, 2014, 9:54 pm EDT
Very cool, Mark !!!

Roger- Thanks, glad you enjoyed it.
"If we knew what it was we were doing, it would not be called research, would it?"
-Albert Einstein
Gutcutter
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Pennsylvania

Posts: 470
Gutcutter on Sep 30, 2014September 30th, 2014, 1:38 pm EDT
It's also time for the great brown autumn sedge out this way. I believe they are Pycnopsyche genus. I've picked up the cases and they look similar to those above.
Any hatch behavior tips for us Easterners?
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Millcreek
Healdsburg, CA

Posts: 344
Millcreek on Sep 30, 2014September 30th, 2014, 3:57 pm EDT
Gutcutter - The cases of Pycnopsyche are similar in appearance to the cases for the immature larvae above, but they're different families of caddis, Calamoceratidae for the Heteroplectron above and Limnephillidae for Pycnopsyche.

Any hatch behavior tips for us Easterners?

About the only hatch behavior I can give you on Pycnopsyche is not to listen to anything I say about them:). I'm just not familiar with them. If your eastern species of Heteroplectron is similar in habits to our western one they seem to emerge sporadically in late summer and early fall. You're more likely to see adults during the daylight hours than in the evening or night.
"If we knew what it was we were doing, it would not be called research, would it?"
-Albert Einstein
Jmd123
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Oscoda, MI

Posts: 2474
Jmd123 on Sep 30, 2014September 30th, 2014, 4:57 pm EDT
"It's also time for the great brown autumn sedge out this way." A.k.a. the "October caddis"? If I can recall those are about a size 10 and a sort of cinnamon-brown. Wish we had more of them around here, as caddis are still hatching nicely on our warmer nights. My last outing on Sunday evening had a solid hatch going and plenty, if rather small, fish feeding on them...too bad the season ends at midnight tonight...


Again Mark, very nice photography!

Jonathon
No matter how big the one you just caught is, there's always a bigger one out there somewhere...
Crepuscular
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Boiling Springs, PA

Posts: 920
Crepuscular on Oct 2, 2014October 2nd, 2014, 9:50 am EDT
COOL!! I love finding Heteroplectron.

Any hatch behavior tips for us Easterners?


Supposedly the Pycnopsyche larvae make there way to the edges to pupate (which really is where you find them anyway since that's where their case materials can be found). Then again "supposedly" the pupae make their way out of the water at the edges at night. I guess that's why we don't really see them in great numbers even when there are tons of larva around. Mostly I see the adults ovipositing during the day. The limited success I've had with adult imitations has been in relatively swift water and short drifts over likely looking spots. I have caught some fish on pupal imitations fished deep.
Millcreek
Healdsburg, CA

Posts: 344
Millcreek on Oct 14, 2014October 14th, 2014, 8:57 pm EDT
Eric and Gutcutter- Since Pycnopsyche seems to be a fairly important seasonal hatch for you guys you might be interested in this dissertation by John Wojtowicz. http://trace.tennessee.edu/cgi/viewcontent.cgi?article=2835&context=utk_graddiss
"If we knew what it was we were doing, it would not be called research, would it?"
-Albert Einstein
Crepuscular
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Boiling Springs, PA

Posts: 920
Crepuscular on Oct 15, 2014October 15th, 2014, 4:48 am EDT
Eric and Gutcutter- Since Pycnopsyche seems to be a fairly important seasonal hatch for you guys you might be interested in this dissertation by John Wojtowicz. http://trace.tennessee.edu/cgi/viewcontent.cgi?article=2835&context=utk_graddiss


Thanks. It's a weird emergence for us. like I said in my post above, we really don't see a ton of adults even in those places where the larvae are everywhere. Mostly what I have experienced is ovipositing adults. I wind up treating them a lot like stoneflies in the way I fish them.And I have some modest success with adult imitations mostly in faster pocket water.

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