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.

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Ephemerella mucronata Mayfly Nymph Ephemerella mucronata Mayfly Nymph

Dorsal view of a Ephemerella mucronata (Ephemerellidae) Mayfly Nymph from the Yakima River in Washington

This is an interesting one. Following the keys in Merritt R.W., Cummins, K.W., and Berg, M.B. (2019) and Jacobus et al. (2014), it keys clearly to Ephemerella. Jacobus et al provide a key to species, but some of the characteristics are tricky to interpret without illustrations. If I didn't make any mistakes, this one keys to Ephemerella mucronata, which has not previously been reported any closer to here than Montana and Alberta. The main character seems to fit well: "Abdominal terga with prominent, paired, subparallel, spiculate ridges." Several illustrations or descriptions of this holarctic species from the US and Europe seem to match, including the body length, tarsal claws and denticles, labial palp, and gill shapes. These sources include including Richard Allen's original description of this species in North America under the now-defunct name E. moffatae in Allen RK (1977) and the figures in this description of the species in Italy.

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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.

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What genus is this Heptageniid?

Female Rhithrogena Mayfly Spinner

9 Pictures

Lateral view of a Female Rhithrogena (Heptageniidae) Mayfly Spinner from the West Branch of the Delaware River in New York

I'm very tentatively (see the connected forum thread) sticking this mayfly in Rhithrogena for now.

Collected June 6, 2007 from the West Branch of the Delaware River in New York

Added by Troutnut on June 8, 2007

Collected June 6, 2007 from the West Branch of the Delaware River in New York and added by Troutnut on June 8, 2007

Troutnut

Administrator
Bellevue, WA

Posts: 2758

Troutnut on Jun 8, 2007June 8th, 2007, 11:10 am EDT

I didn't even recognize it as a member of that family at first, but it seems to be the only option. The hind tarsus is distinctly 5-segmented, which I verified under the microscope because you can't see it very well on my photos. However, I because it's a female spinner I can't key it to genus using the Merrit & Cummins keys. Does anyone just recognize it?

I found it drifting, nearly dead on the surface at about 5pm on a hot afternoon.

Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist

Konchu

Site Editor
Indiana

Posts: 498

Konchu on Jun 9, 2007June 9th, 2007, 2:07 am EDT

Ignoring all other details, the body shape & color and leg markings resemble some Epeorus and Rhithrogena. Possibly Rhithrogena is the closest. I collected some about like this with male spinners a few weeks ago in Tennessee.

Troutnut

Administrator
Bellevue, WA

Posts: 2758

Troutnut on Jun 9, 2007June 9th, 2007, 4:16 am EDT

I was considering Rhithrogena too because it has a few of those anastomosed crossveins. They just aren't as prominent as I've seen in most illustrations, which gave me cause for doubt. I'll tentatively stick it in there for now.

Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist

Tana
Madrid España

Posts: 1

Tana on Jan 31, 2009January 31st, 2009, 9:15 pm EST

Hola, Creo que no es posible determinar un insecto de estas caracteristicas en esste estado, ha tantos tipos de Rhithrogena que no podria saber si realmente es alguna, en estados adultos yo en España recomiendo imitar color y tamaño, a mi me parece que se puede sustituir por la March Bronw, recomiendo leer esto:
http://images.google.es/imgres?imgurl=http://www.cpdrioarga.com/prueba/naturaleza/moscasnaturales/efemeras/heptagenidos/imagenes/heptagenido%2520(subimago)%2520hembra%25202.jpg&imgrefurl=http://www.cpdrioarga.com/prueba/naturaleza/moscasnaturales/efemeras/heptagenidos/heptagenidos.html&usg=__99R-yRByWLBw2Ny4WA5Ygf_8yjs=&h=450&w=600&sz=55&hl=es&start=67&um=1&tbnid=J0oT_Bxb0Cv5xM:&tbnh=101&tbnw=135&prev=/images%3Fq%3DRhithrogena%26start%3D54%26ndsp%3D18%26um%3D1%26hl%3Des%26lr%3Dlang_es%26rlz%3D1T4HPEB_esES305ES305%26sa%3DN

Un saludo a todos Tana

Taxon

Site Editor
Plano, TX

Posts: 1311

Taxon on Feb 1, 2009February 1st, 2009, 6:24 am EST

Although the translation may be less than perfect,
this is (more or less) what Tana is saying
when translated to English:

Hello, I think it is not possible to identify an insect of its kind in this state,
has many different types of Rhithrogena could not really tell if any,
adult I recommend imitate Spain in color and size,
I find that you can replaced by the March Brown,
I read this:

Greetings,

Tana

Best regards,
Roger Rohrbeck
www.FlyfishingEntomology.com