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Insect Order Ephemeroptera (Mayflies)

Mayflies

Caddisflies

Stoneflies

Taxonomic Navigation -?-

Kingdom Animalia (Animals)

» Phylum Arthropoda (Arthropods)

» Class Insecta (Insects)

» Order Ephemeroptera (Mayflies)

Family in Ephemeroptera
AmeletidaeBrown Duns	0	0
BaetidaeBlue-Winged Olives	0	10
BaetiscidaeArmored Mayflies	0	1
CaenidaeAngler's Curses	0	0
EphemerellidaeHendricksons, Sulphurs, PMDs, BWOs	0	37
EphemeridaeHexes and Big Drakes	0	3
HeptageniidaeMarch Browns, Cahills, Quill Gordons	0	11
IsonychiidaeSlate Drakes	0	0
LeptohyphidaeTricos	0	1
LeptophlebiidaeBlue Quills and Mahogany Duns	0	0
MetretopodidaePseudo-Gray Drakes	0	0
Neoephemeridae	0	0
PolymitarcyidaeWhite Flies	0	0
PotamanthidaeGolden Drakes	0	0
SiphlonuridaeGray Drakes	0	3

8 families aren't included.

Common Name

Match	Common Name
	Mayflies

Pictures Below ↓

This is page 60 of specimens of Ephemeroptera. Visit the main Ephemeroptera page for:

The behavior and habitat of Ephemeroptera.
67 underwater pictures of Ephemeroptera.

Pictures of 828 Mayfly Specimens:

Specimen Page:1...596061...84

Male Ephemerella tibialis (Little Western Dark Hendrickson) Mayfly Dun

View 9 Pictures

Collected July 9, 2019 from Rock Creek in Montana
Added to Troutnut.com by Troutnut on July 18, 2019

Female Cinygmula ramaleyi (Small Western Gordon Quill) Mayfly Spinner

View 8 Pictures

Collected August 3, 2020 from Star Hope Creek in Idaho
Added to Troutnut.com by Troutnut on August 19, 2020

Ephemerella tibialis (Little Western Dark Hendrickson) Mayfly Nymph

View 6 Pictures

Collected July 25, 2019 from Mystery Creek #249 in Washington
Added to Troutnut.com by Troutnut on July 26, 2019

Baetis tricaudatus (Blue-Winged Olive) Mayfly Nymph

View 20 PicturesA nymph of the same species as this one emerged into a dun in my studio so I got photos of both stages.

NOTE: I missed an important key characteristic the first time I tried to identify this one (robust setae (Seta: Little hairs on insects.) on the abdominal sternites (

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.), which were harder to see than I expected but are clearly present), so I went on a bit of a wild goose chase and landed at a dead end. After spotting that characteristic, this one keys more straightforwardly to either Baetis tricaudatus or the Baetis piscatoris complex. It doesn't seem to be a perfect fit for either one in the key, but I'm going with tricaudatus based on range and abundance. It's not certain.

However, I'm leaving the flawed analysis below with this disclaimer, because some aspects of how I approached that dead end might be informative in the future.

----Incorrect analysis below----

After spending a lot of time with this one under my shiny new microscope, I'm still not quite sure what it is. I botched my attempt to expose the mouth parts that might make the ID more definitive. Based on the key in Webb et al 2018's "Baetis Larvae of North America," here's my reasoning at each key couplet.

Couplet 1. The pronotum (Pronotum: The top of the insect prothorax.) lacks dark, submedian U-shaped markings. Also, if I were to follow through to couplet 2, there seem to be characteristics that rule out each of the options: the intercalaris complex is ruled out by the abdominal markings, and the caudal (Caudal: Toward the posterior tip of the body.) filaments have neither a dark median band (ruling out the flavistriga complex) nor uniform pale coloration (ruling out Baetis notos). This sends me with decent confidence to couplet 4.

Couplet 4. I cannot find robust setae (Seta: Little hairs on insects.) in my microscope on the scapes, pedicels, paraprocts, or sterna. I also do not see a pair of dark, bilobed markings on the pronotum (Pronotum: The top of the insect prothorax.). Unless I overlooked these characteristics, proceed to couplet 9.

Couplet 9. Abdominal tergum (Tergum: the dorsal part of an abdominal segment or segments (terga). Also used to describe the entire abdominal dorsum or the thoracic dorsal segments of Odonata.) 5 is a bit paler than adjacent terga (Tergum: the dorsal part of an abdominal segment or segments (terga). Also used to describe the entire abdominal dorsum or the thoracic dorsal segments of Odonata.), but "distinctly paler"? The figure for Baetis alius in the paper, as well as a very nice picture posted by Millcreek in the forum here, shows that Baetis alius would have darker tergites (

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.) surrounding #5. So proceed to couplet 11.

Couplet 11. The length of the gills is obviously less than 2X their width. This leads to the Baetis vernus complex, which could include that species or Baetis brunneicolor. This key doesn't say how to tell those species apart.

Switching over to Burien et al 2018 as the source, the characteristics used to distinguish vernus from brunneicolor seem to rule out either one. Brunneicolor should have more uniformly brown abdominal tergites (

One tergite 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.) length is about 3.8x its width.

Also worth noting: In the genus ID, I thought I could see the villipore in my microscope, but I'm not sure. If I back out of Baetis altogether and assume there's no villipore, I end up at Fallceon, but this specimen doesn't seem to have the frontal keel on the head that's supposed to be present on Fallceon quilleri. So that seems like a dead end as well.

Collected September 12, 2020 from the Yakima River in Washington
Added to Troutnut.com by Troutnut on September 19, 2020

Female Baetisca laurentina (Armored Mayfly) Mayfly Spinner

View 5 Pictures

Collected May 28, 2005 from the Namekagon River in Wisconsin
Added to Troutnut.com by Troutnut on May 24, 2006

Female Ephemerella excrucians (Pale Morning Dun) Mayfly Dun

View 7 PicturesAlthough there is no key to female duns, I'm calling this dun Ephemerella excrucians because I collected several mature nymphs of that species on the same trip.

Collected July 4, 2020 from Mystery Creek #249 in Washington
Added to Troutnut.com by Troutnut on July 12, 2020

Male Acentrella insignificans (Tiny Blue-Winged Olive) Mayfly Nymph

View 10 PicturesAnother nymph probably of the same species as this one emerged and was photographed as a dun and partly-molted spinner.

Collected September 12, 2020 from the Yakima River in Washington
Added to Troutnut.com by Troutnut on September 19, 2020

Drunella grandis (Western Green Drake) Mayfly Nymph

View 5 Pictures

Collected July 4, 2020 from Mystery Creek #249 in Washington
Added to Troutnut.com by Troutnut on July 12, 2020

Female Maccaffertium (March Browns and Cahills) Mayfly Dun

View 9 Pictures

Collected September 5, 2006 from the Neversink River in New York
Added to Troutnut.com by Troutnut on October 3, 2006

Cinygmula (Dark Red Quills) Mayfly Nymph

View 8 Pictures

Collected June 13, 2019 from the South Fork Snoqualmie River in Washington
Added to Troutnut.com by Troutnut on June 14, 2019

Specimen Page:1...596061...84

Jargon Defined:

Caudal: Toward the posterior tip of the body.

Dun: Mayflies have two adult stages. They first emerge from the water as duns (scientifically known as the subimago stage). They then molt into the spinner (imago) stage, in which they mate and die. Sometimes the word "dun" is confusingly used to refer to a brownish gray color in fly tying materials.

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.

Larvae: 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.

Nymph: The juvenile, underwater stages of mayflies, stoneflies, dragonflies, and damselflies and other aquatic insects whose juvenile stages are covered by hard exoskeletons. The word can also refer to the fishing flies which imitate these creatures, in which case it is used as a blanket term for flies imitating any underwater stage of an invertebrate (except for crayfish and leeches).

Pronotum: The top of the insect prothorax.

Setae: Little hairs on insects.

Spinner: There are two winged stages of adult mayflies. They emerge from the water as duns, molt on land (usually) into their fully mature stage, spinners. As spinners, they mate, lay eggs, and die.

One sternite of this Isonychia bicolor mayfly spinner is highlighted in red.

Sternites: The bottom (ventral) part of a single segment on an insect's abdomen.

One tergite of this Isonychia bicolor mayfly spinner is highlighted in red.

Tergites: 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.

Tergum: the dorsal part of an abdominal segment or segments (terga). Also used to describe the entire abdominal dorsum or the thoracic dorsal segments of Odonata.