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.

Stream photos

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Caddisfly Species Hydatophylax argus (Giant Cream Pattern-Wing Sedge)

This is an especially large species, with pupae and adults up to hook size 2.

Where & when

Time of year : June through fall

Preferred waters: Small streams

In 53 records from GBIF, adults of this species have mostly been collected during May (53%), April (21%), and June (21%).

In 13 records from GBIF, this species has been collected at elevations ranging from 627 to 2740 ft, with an average (median) of 2008 ft.

Species Range

source

Map of specific collection sites

Hatching behavior

Time of day : Morning

Gary LaFontaine reports in Caddisflies that his trout stomach samples held many Hydatophylax argus pupae during their emergence in the East.

Specimens of the Caddisfly Species Hydatophylax argus

1 Female Adult

Female Hydatophylax argus Caddisfly Adult

12 Pictures

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

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

Start a Discussion of Hydatophylax argus

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.