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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
Baetis

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.

Dorsal view of a Zapada cinctipes (Nemouridae) (Tiny Winter Black) Stonefly Nymph from the Yakima River in Washington
Nymphs of this species were fairly common in late-winter kick net samples from the upper Yakima River. Although I could not find a key to species of Zapada nymphs, a revision of the Nemouridae family by Baumann (1975) includes the following helpful sentence: "2 cervical gills on each side of midline, 1 arising inside and 1 outside of lateral cervical sclerites, usually single and elongate, sometimes constricted but with 3 or 4 branches arising beyond gill base in Zapada cinctipes." This specimen clearly has the branches and is within the range of that species.
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 Species Amiocentrus aspilus (Little Western Weedy Water Sedges)

This species produces fishable hatches across the West.

I encountered them in mid-August on the Henry's Fork, mating in thick swarms up and down the bank of the Harriman Ranch reach. However, millions of Tricorythodes mayflies found their way onto the water that same morning and it's unclear if the trout were seeing and responding to the caddisflies at all.

Where & when

Time of year : March to October; LaFontaine reports peaks in late June and in September

Preferred waters: Best in spring creeks

In 23 records from GBIF, adults of this species have mostly been collected during July (35%), August (30%), May (13%), June (9%), and March (9%).

In 4 records from GBIF, this species has been collected at elevations of 6060, 6250, 6726, and 7005 ft.

Species Range

Larva & pupa biology

Substrate: Vegetation

Larvae of this species are especially prone to behavioral drift early in the season.

Specimens of the Caddisfly Species Amiocentrus aspilus

1 Adult

Start a Discussion of Amiocentrus aspilus

References

Caddisfly Species Amiocentrus aspilus (Little Western Weedy Water Sedges)

Taxonomy
Species Range
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