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Lateral view of a Male Baetis (Baetidae) (Blue-Winged Olive) Mayfly Dun from Mystery Creek #43 in New York
Blue-winged Olives

Tiny Baetis mayflies are perhaps the most commonly encountered and imitated by anglers on all American trout streams due to their great abundance, widespread distribution, and trout-friendly emergence habits.

Lateral view of a Female Sweltsa borealis (Chloroperlidae) (Boreal Sallfly) Stonefly Adult from Harris Creek in Washington
I was not fishing, but happened to be at an unrelated social event on a hill above this tiny creek (which I never even saw) when this stonefly flew by me. I assume it came from there. Some key characteristics are tricky to follow, but process of elimination ultimately led me to Sweltsa borealis. It is reassuringly similar to this specimen posted by Bob Newell years ago. It is also so strikingly similar to this nymph from the same river system that I'm comfortable identifying that nymph from this adult. I was especially pleased with the closeup photo of four mites parasitizing this one.
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.
Troutnut is a project started in 2003 by salmonid ecologist Jason "Troutnut" Neuswanger to help anglers and fly tyers unabashedly embrace the entomological side of the sport. Learn more about Troutnut or support the project for an enhanced experience here.

Caddisfly Species Helicopsyche borealis (Speckled Peters)

This is the only important trout stream species of Helicopsyche. It has an unusual wing characteristic, described by Gary LaFontaine in Caddisflies:

The adult appears different in flight from other caddisflies because the top set of wings is attached to the bottom by a row of hooks, so the four wings beat together, not as two spread-out sets.

Where & when

Time of year : Early May through July

Preferred waters: Rivers or lakes; best in spring creeks and large rivers

The emergence of this species lasts a few weeks in any given location. It begins in the East in early May and lasts through June, while in the West it begins in mid-June and lasts through early July.

In 137 records from GBIF, adults of this species have mostly been collected during June (23%), July (21%), August (19%), May (12%), September (9%), and April (8%).

In 92 records from GBIF, this species has been collected at elevations ranging from 195 to 10194 ft, with an average (median) of 3509 ft.

Species Range

Hatching behavior

Time of day : Evening

Egg-Laying behavior

Time of day: Evening

LaFontaine gives a slightly confusing account of the ovipositing behaivor of this species in Caddisflies, suggesting that they may flutter around on or near the water's surface looking for solid objects to attach their eggs to, or may drop them in the water. Swisher and Richards give a clearer picture in Selective Trout:

During egg laying, the females float in the surface close to the banks, crawl underwater, and flop on the surface to oviposit. They then ride the water serenely in the normal resting position, and trout take them with gentle rises.

Larva & pupa biology

Diet: Algae, detritus, animal matter

Environmental tolerance: Very tolerant: can thrive in both cold water and hot springs up to 110°F

Shelter type: Coiled sand case shaped like a snail shell

Specimens of the Caddisfly Species Helicopsyche borealis

1 Female Adult
1 Pupa

Start a Discussion of Helicopsyche borealis


Caddisfly Species Helicopsyche borealis (Speckled Peters)

Species Range
Common Name
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