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> > Stenonema femoratum male spinner

This topic is about the Mayfly Genus Stenonema

"Stenonema" as we knew it is no more.

The name is still popular with anglers, primarily due to extensive literary use of the name over the years. It has attained an almost iconic status. Entomologists, whose concern is rightly science not angling tradition, have since moved all the best-known species to new genera. As an aid to anglers familiar with the old names who have come to this page looking for information, please redirect to the following pages by clicking on the highlighted names:

March Brown (Stenonema vicarium) - Maccaffertium vicarium
Gray Fox (Stenonema fuscum) - Maccaffertium vicarium
Light Cahill (Stenonema canadense) - Stenacron interpunctatum

Only one species (and of minor importance to anglers) remains in the Stenonema genus: Stenonema femoratum. You can find additional information on this species by going to its hatch page.

The Discussion

Jmw975May 21st, 2012, 8:53 am
Guelph, Ontario

Posts: 20
Male Stenonema femoratum collected from the Grand River, Ontario. Note the 3 spots at the hind margins of each of the abdominal segments.

EntomanMay 21st, 2012, 12:03 pm
Site Editor
Northern CA & ID

Posts: 2604
Thanks Jeff, for the excellent photo and determination. Readers note that besides the three spots that are clearly seen, spots are also just visible on seg's 3 and 8. The dark transverse dashes are a little harder to make out, but they look to be present as well. The crowded crossveins below the bulla are also indicative of femoratum. This is the last Stenonema species left in what is now the least important genus (to anglers) of the related group. See the genus topic article as well as the family article in the hatch encyclopedia for a brief explanation.
"It's not that I find fishing so important, it's just that I find all other endeavors of Man equally unimportant... And not nearly as much fun!" Robert Traver, Anatomy of a Fisherman
Jmw975May 21st, 2012, 2:24 pm
Guelph, Ontario

Posts: 20
Thanks. Did I post this in the right place? I was hoping to have it show up under the species in the aquatic insect encyclopedia.

Here's a lateral shot of another male specimen:
Between the two photos you can clearly see the crowded crossveins in the bulla and the three transverse spots/dashes on the abdominal terga.

A preserved nymph showing the highly distinctive sternal colour pattern:

and now I'm going fishin' :)

EntomanMay 21st, 2012, 2:43 pm
Site Editor
Northern CA & ID

Posts: 2604
Thanks for the ventral! They're hard to find and much easier to work with than descriptions. BTW, you posted in the right place. See PM just sent.
"It's not that I find fishing so important, it's just that I find all other endeavors of Man equally unimportant... And not nearly as much fun!" Robert Traver, Anatomy of a Fisherman

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