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.

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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

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

Female Hydatophylax argus (Giant Cream Pattern-Wing Sedge) Caddisfly Adult

12 Pictures

I had some trouble working through the genus key for this one because I'm not great at interpreting caddis wing venation. Fortunately, figure 19.707 in An Introduction to the Aquatic Insects of North America (Fifth Edition) shows the distinctive color pattern of the striking forewings on Hydatophylax argus, which is a perfect match for the pattern as well as venation. As there are no other species in that genus in this area, I can be pretty confident in the species ID.

Collected June 11, 2021 from the Teal River in Wisconsin

Added by Troutnut on June 12, 2021

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References

LaFontaine, Gary. 1981. Caddisflies. The Lyons Press.
Merritt R.W., Cummins, K.W., and Berg, M.B. 2019. An Introduction to the Aquatic Insects of North America (Fifth Edition). Kendall/Hunt Publishing Company.
Swisher, Doug and Carl Richards. 2000. Selective Trout. The Lyons Press.