The East Fork Big Lost River

Mayflies

Caddisflies

Stoneflies

Closeup insects from the East Fork Big Lost River

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Ephemerella tibialis (Little Western Dark Hendrickson) Mayfly Nymph

View 13 Pictures

Collected August 3, 2020 from the East Fork Big Lost River in Idaho
Added to Troutnut.com by Troutnut on August 19, 2020

Arctopsyche grandis (Great Gray Spotted Sedge) Caddisfly Larva

View 14 PicturesAt first I had trouble believing this giant Hydropsychidae larva was actually a member of its family, because of the size. I had never seen such a thing. It turned out to be a member of this exceptionally large species with a fitting name, grandis.

Collected August 3, 2020 from the East Fork Big Lost River in Idaho
Added to Troutnut.com by Troutnut on August 19, 2020

Attenella margarita (Little Western Blue-Winged Olive) Mayfly Nymph

View 7 PicturesNotes from the microscope on the ID: Maxillary palp (

The palp on the maxilla of an Ephemerella nymph (detached and photographed under a microscope) is highlighted in red here.

Palp: A long, thin, often segmented appendage which can protrude from certain insect mouth parts such as the maxillae. Also known as the < />palpus.) is present, distinctly 2-segmented, but very small. Gills on segment 4-7. This specimen has some unfortunate damage to the abdomen, but it's the only one I found in my sample.

Collected August 3, 2020 from the East Fork Big Lost River in Idaho
Added to Troutnut.com by Troutnut on August 19, 2020

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Jargon Defined:

Abdomen: The rear and usually the longest (ten-segmented in mayflies) portion of an insect's body, to which the tails are attached.

Larva: Many classes of aquatic insects, such as caddisflies, midges, craneflies, dobsonflies, alderflies, and many more, are known as "larvae" rather than "nymphs" in their juvenile stages. They have mostly soft bodies rather than hard exoskeletons. These insects also advance through a "pupa" stage before reaching adulthood.

The palp on the maxilla of an Ephemerella nymph (detached and photographed under a microscope) is highlighted in red here.

Palp: A long, thin, often segmented appendage which can protrude from certain insect mouth parts such as the maxillae. Also known as the < />palpus.

Trout Streams > Idaho > The East Fork Big Lost River

Closeup insects from the East Fork Big Lost River

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Jargon Defined:

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