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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 Holocentropus (Polycentropodidae) Caddisfly Larva from the Yakima River in Washington
This one seems to tentatively key to Holocentropus, although I can't make out the anal spines in Couplet 7 of the Key to Genera of Polycentropodidae Larvae nor the dark bands in Couplet 4 of the Key to Genera of Polycentropodidae Larvae, making me wonder if I went wrong somewhere in keying it out. I don't see where that could have happened, though. It might also be that it's a very immature larva and doesn't possess all the identifying characteristics in the key yet. If Holocentropus is correct, then Holocentropus flavus and Holocentropus interruptus are the two likely possibilities based on range, but I was not able to find a description of their larvae.
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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Caddisfly Genus Hydatophylax (Giant Cream Pattern-Wing Sedges)

These are huge caddisflies. The larvae may be nearly an inch and a half long and build three-inch cases. Hook sizes 4-6 are appropriate for the pupae.

Where & when

Time of year : Late May to fall in the East; August to October in the West

Preferred waters: Medium to large streams

In 69 records from GBIF, adults of this genus have mostly been collected during June (46%), July (22%), May (19%), and August (7%).

In 14 records from GBIF, this genus has been collected at elevations ranging from 33 to 2740 ft, with an average (median) of 2008 ft.

Genus Range

Hatching behavior

Time of day : Morning

Trout may feed on the pupae of this genus.

Egg-Laying behavior

The egg-laying adults are not important.

Larva & pupa biology

Diet: Woody debris

Current speed: Slow

Specimens of the Caddisfly Genus Hydatophylax

1 Female Adult

Start a Discussion of Hydatophylax

References

Caddisfly Genus Hydatophylax (Giant Cream Pattern-Wing Sedges)

Taxonomy
Species in Hydatophylax: Hydatophylax argus, Hydatophylax hesperus
2 species (Hydatophylax variabilis and Hydatophylax victor) aren't included.
Genus Range
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