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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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Dorsal view of a Rhyacophila fuscula (Rhyacophilidae) (Green Sedge) Caddisfly Larva from the Long Lake Branch of the White River in Wisconsin
I collected this larva and several like it from the same stream and on the same day as this pupa. I suspect they're the same species.
Knoxville TN

Posts: 51
Litobrancha on Sep 5, 2006September 5th, 2006, 8:44 am EDT
Looks like Rhyacophila fuscula. Wonderful bug.
boulder colorado

Posts: 2
Jwatersphd on Jun 23, 2007June 23rd, 2007, 2:35 pm EDT
i am curious how to tell rhyacophila from macronema and whether it makes any difference either in terms of size or behavior. in schweibert's first volume from years ago they look very similar. i am awaiting his new two volume set but in the meantime would be curious i if anyone knows. there is definitely a green caddis that is quite prevalent on the gunnison in the black canyon and probably gorge below but i have not been especially successful at devising a good imitation. after looking at oliver edwards's video on czech nymphing, however, i am thinking the big problem is that i did not tie in such a method as to emphasize the heavily segmented body.
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Site Editor
Plano, TX

Posts: 1311
Taxon on Jun 23, 2007June 23rd, 2007, 6:32 pm EDT
Dr. Waters-

Rhyacophila are in the family of free-living caddisflies (Rhyacophilidae), whose larvae are characterized by: only pronotum having a sclerotized plate, mesonotum and metanotum being entirely membranous; sclerotized plate on top of abdominal segment nine; anal prolegs long with large claws.

Macronema (now Macrostemum, at least for those species of interest to flyfishers) are in the family of common net-spinner caddisflies (Hydropsycidae), whose larvae are characterized by: sclerotized plates on notum of all three thoracic segments; anal prolegs terminating in a brush of long setae.

Incidentally, no Macrostemum species are known from Colorado.
Best regards,
Roger Rohrbeck
Posts: 2
Ov10fac on Jul 30, 2019July 30th, 2019, 7:15 am EDT
What is the approximate length and width of this fly. I used to fish something similar to this on the South Platte in Colorado. Seems the ones I fished were a little more brown.
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Bellevue, WA

Posts: 2758
Troutnut on Jul 30, 2019July 30th, 2019, 7:29 am EDT
This one is over an inch long. The genus Rhyacophila is the largest (in number of species) genus of caddisflies, with several dozen different species in North America if I recall correctly. You very likely saw one of the other species of this genus on the South Platte.
Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist

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