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Mayfly Genus Ameletus (Brown Duns)

Taxonomic Navigation -?-
Species in AmeletusNumber of SpecimensNumber of Pictures
Ameletus celerBrown Dun12
Ameletus lineatusBrown Dun00
Ameletus ludensBrown Dun322
Ameletus oregonensisBrown Dun24
Ameletus sparsatusBrown Dun00
Ameletus subnotatusBrown Dun11
Ameletus validusBrown Dun00
Ameletus veloxBrown Dun00
Ameletus vernalisBrown Dun55

25 species aren't included.
Common Name
MatchCommon Name
***Brown Duns
Pictures Below

This is page 2 of specimens of Ameletus. Visit the main Ameletus page for:

  • The behavior and habitat of Ameletus.

Pictures of 21 Mayfly Specimens in the Genus Ameletus:

Specimen Page:123
Ameletus celer (Brown Dun) Mayfly NymphAmeletus celer (Brown Dun) Mayfly Nymph View 2 Pictures
Collected July 14, 2011 from Swamp Creek in Oregon
Added to Troutnut.com by Bnewell on July 15, 2011
Ameletus (Brown Duns) Mayfly NymphAmeletus (Brown Duns) Mayfly Nymph View 7 PicturesI think this is a pretty early instar (Instar: Many invertebrates molt through dozens of progressively larger and better-developed stages as they grow. Each of these stages is known as an instar. Hard-bodied nymphs typically molt through more instars than soft-bodied larvae.) Ameletus nymph. It's certainly a striking one.
Collected May 6, 2007 from Mongaup Creek in New York
Added to Troutnut.com by Troutnut on May 18, 2007
Female Ameletus (Brown Duns) Mayfly SpinnerFemale Ameletus (Brown Duns) Mayfly Spinner View 13 PicturesI found this female already spent (Spent: The wing position of many aquatic insects when they fall on the water after mating. The wings of both sides lay flat on the water. The word may be used to describe insects with their wings in that position, as well as the position itself.) and nearly dead, laying in the surface film of a very tiny spring seep (inch-deep water) in the valley of a very small trout stream.
Collected July 28, 2019 from Mystery Creek #199 in Washington
Added to Troutnut.com by Troutnut on July 30, 2019
Ameletus vernalis (Brown Dun) Mayfly NymphAmeletus vernalis (Brown Dun) Mayfly Nymph View 9 PicturesI keyed this one out using the Alberta species key from Zloty & Pritchard 1997.

Notes from the ID include:

1. Posterior (Posterior: Toward the back of an organism's body. The phrase "posterior to" means "in back of.") margin of sternites (
One sternite of this Isonychia bicolor mayfly spinner is highlighted in red.
One sternite of this Isonychia bicolor mayfly spinner is highlighted in red.
Sternite: The bottom (ventral) part of a single segment on an insect's abdomen.
)
6-8 without spines
2. Mesal (Mesal: Toward the middle.) gill extension "well developed"
3. Basil third of caudal (Caudal: Toward the posterior tip of the body.) filaments pale
4. Anterior (Anterior: Toward the front of an organism's body. The phrase "anterior to" means "in front of.") surface of front femora (
The femur of this Isonychia bicolor mayfly spinner is highlighted in red.
The femur of this Isonychia bicolor mayfly spinner is highlighted in red.
Femur: The main segment of an insect's leg close to the body, in between the tibia and the trochanter.
)
mostly pale
5. Dark band on caudal (Caudal: Toward the posterior tip of the body.) filaments begins around segment 20
6. Final instars (Instar: Many invertebrates molt through dozens of progressively larger and better-developed stages as they grow. Each of these stages is known as an instar. Hard-bodied nymphs typically molt through more instars than soft-bodied larvae.) early season

This one keys out pretty cleanly to Ameletus vernalis except the color pattern on the tergites (
One tergite of this Isonychia bicolor mayfly spinner is highlighted in red.
One tergite of this Isonychia bicolor mayfly spinner is highlighted in red.
Tergite: The top (dorsal) part of a single segment on an insect's abdomen when it consists of a single chitinous plate (sclerite), or an individual sclerite if the segment has more than one.
)
doesn't match. However, two species known in Washington aren't included in the key. Of those two, Ameletus vancouverensis would be too small (adult body length 9 mm), but Ameletus andersoni (currently documented only from a spring in Cowlitz County) has a wide range of sizes and emergence times that could be compatible with this one. So I can't rule that species out, but Ameletus vernalis seems the most likely.
Collected April 9, 2021 from the Yakima River in Washington
Added to Troutnut.com by Troutnut on April 12, 2021
Specimen Page:123
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