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Arthropod Class Insecta (Insects)

Mayflies

Caddisflies

Stoneflies

Taxonomic Navigation -?-

Kingdom Animalia (Animals)

» Phylum Arthropoda (Arthropods)

» Class Insecta (Insects)

Order in Insecta
ColeopteraBeetles	0	1
DipteraTrue Flies	0	9
EphemeropteraMayflies	0	67
HemipteraTrue Bugs	0	7
HymenopteraAnts, Bees, and Wasps	0	0
LepidopteraMoths	0	0
MegalopteraHellgrammites, Dobsonflies, and Alderflies	0	0
Odonata-AnisopteraDragonflies	0	0
Odonata-ZygopteraDamselflies	0	0
OrthopteraGrasshoppers and Crickets	0	0
PlecopteraStoneflies	0	6
Psocodea	0	0
TrichopteraCaddisflies	0	55

1 order isn't included.

Common Name

Match	Common Name
	Insects

Pictures Below ↓

This is page 93 of specimens of Insecta. Visit the main Insecta page for:

The behavior and habitat of Insecta.
114 underwater pictures of Insecta.

Pictures of 1229 Insect Specimens:

Specimen Page:1...929394...124

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

Male Maccaffertium (March Browns and Cahills) Mayfly Dun

View 6 PicturesI collected this male dun together with a female.

Collected May 27, 2005 from the Namekagon River in Wisconsin
Added to Troutnut.com by Troutnut on May 22, 2006

Male Epeorus (Little Maryatts) Mayfly Dun

View 7 PicturesThis Epeorus dun managed to emerge successfully even though it had apparently long several legs at some point and only partially grown them back.

Collected May 15, 2007 from the West Branch of the Delaware River in New York
Added to Troutnut.com by Troutnut on May 18, 2007

Female Strophopteryx fasciata (Mottled Willowfly) Stonefly Adult

View 5 PicturesSeveral stoneflies of this species were the first adult insects I found in 2004 when I started this site. The hatch was sparse but lasted a good part of the day, and I noted a few good rises despite the early season cold. They ended up struggling on the water's surface fairly often.

Collected March 16, 2004 from the Namekagon River in Wisconsin
Added to Troutnut.com by Troutnut on January 25, 2006

Male Baetidae (Blue-Winged Olives) Mayfly Dun

View 3 Pictures

Collected May 23, 2004 from unknown in Wisconsin
Added to Troutnut.com by Troutnut on January 25, 2006

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

Female Paraleptophlebia (Blue Quills and Mahogany Duns) Mayfly Dun

View 5 Pictures

Collected May 7, 2005 from the Beaverkill River in New York
Added to Troutnut.com by Troutnut on May 16, 2006

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

Philopotamidae Caddisfly Larva

View 2 Pictures

Collected March 13, 2005 from Cascadilla Creek in New York
Added to Troutnut.com by Troutnut on April 5, 2006

Male Baetisca laurentina (Armored Mayfly) Mayfly Dun

View 5 Pictures

Collected May 22, 2004 from the Namekagon River in Wisconsin
Added to Troutnut.com by Troutnut on January 25, 2006

Specimen Page:1...929394...124

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.