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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 Amphizoa (Amphizoidae) Beetle Larva from Sears Creek in Washington
This is the first of it's family I've seen, collected from a tiny, fishless stream in the Cascades. The three species of this genus all live in the Northwest and are predators that primarily eat stonefly nymphs Merritt R.W., Cummins, K.W., and Berg, M.B. (2019).
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.

Callibaetis ferrugineus (Speckled Dun) Mayfly Nymph Pictures

This nymph was one of a horde I could see cruising the still shallows of a cold tailwater, mixed in with an intense emergence of duns. It's one of four specimens I photographed together from the same hatch, also including a male dun, a female dun, and a male spinner.

This nymph keys to either Callibaetis ferrugineous or Callibaetis pallidus. The lack of a darkened preapical band on the femora would suggest pallidus, but I can't definitively make out the "single seta" on the outer, ventral apex of any of the tarsi, the length of which is supposedly a more reliable characteristic to tell the species spart. I can maybe make something out on one of the legs at the highest magnification, and its dimensions would suggest ferrugineous.

Dorsal view of a Callibaetis ferrugineus (Baetidae) (Speckled Dun) Mayfly Nymph from Mystery Creek #304 in Idaho
Lateral view of a Callibaetis ferrugineus (Baetidae) (Speckled Dun) Mayfly Nymph from Mystery Creek #304 in Idaho
Callibaetis ferrugineus (Baetidae) (Speckled Dun) Mayfly Nymph from Mystery Creek #304 in Idaho
Callibaetis ferrugineus (Baetidae) (Speckled Dun) Mayfly Nymph from Mystery Creek #304 in Idaho
Callibaetis ferrugineus (Baetidae) (Speckled Dun) Mayfly Nymph from Mystery Creek #304 in Idaho
Ventral view of a Callibaetis ferrugineus (Baetidae) (Speckled Dun) Mayfly Nymph from Mystery Creek #304 in Idaho
Callibaetis ferrugineus (Baetidae) (Speckled Dun) Mayfly Nymph from Mystery Creek #304 in Idaho
Callibaetis ferrugineus (Baetidae) (Speckled Dun) Mayfly Nymph from Mystery Creek #304 in Idaho
Callibaetis ferrugineus (Baetidae) (Speckled Dun) Mayfly Nymph from Mystery Creek #304 in Idaho
Ruler view of a Callibaetis ferrugineus (Baetidae) (Speckled Dun) Mayfly Nymph from Mystery Creek #304 in Idaho The smallest ruler marks are 1 mm.
Gills 3–6 from the right side

Callibaetis ferrugineus (Baetidae) (Speckled Dun) Mayfly Nymph from Mystery Creek #304 in Idaho
Left foreleg, dorsal view

Callibaetis ferrugineus (Baetidae) (Speckled Dun) Mayfly Nymph from Mystery Creek #304 in Idaho
Ventral view of left foretarsus

Callibaetis ferrugineus (Baetidae) (Speckled Dun) Mayfly Nymph from Mystery Creek #304 in Idaho
Ventral view of right foretarsus

Callibaetis ferrugineus (Baetidae) (Speckled Dun) Mayfly Nymph from Mystery Creek #304 in Idaho

This mayfly was collected from Mystery Creek #304 in Idaho on July 23rd, 2022 and added to Troutnut.com by Troutnut on January 15th, 2023.


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Callibaetis ferrugineus (Speckled Dun) Mayfly Nymph Pictures

Collection details
Location: Mystery Creek #304, Idaho
Date: July 23rd, 2022
Added to site: January 15th, 2023
Author: Troutnut
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