Hex Mayflies
Hexagenia limbata
The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large brown trout that only touch streamers for the rest of the year.
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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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CalebBoyle has attached these 2 pictures to aid in identification. The message is below.
CalebBoyle on Mar 30, 2007March 30th, 2007, 2:53 pm EDT
Hello all,
This is my first time posting and I must agree with everyoen, this is the best aquatic entomology site by far for the flyfisherman. I have a mayfly hatch from my aquarium that is quite unique in its coloration. I'm pretty sure its a maccaffertium species, but I'm not sure which one. Anyone have some ideas?
This is my first time posting and I must agree with everyoen, this is the best aquatic entomology site by far for the flyfisherman. I have a mayfly hatch from my aquarium that is quite unique in its coloration. I'm pretty sure its a maccaffertium species, but I'm not sure which one. Anyone have some ideas?
Konchu on Mar 30, 2007March 30th, 2007, 3:01 pm EDT
or Stenacron??? I just moved and all my notes/books are tucked away in boxes, but that is my initial guess based on your photos. Nice pictures, by the way.
CalebBoyle on Mar 30, 2007March 30th, 2007, 3:07 pm EDT
It Could be. Is there a good key to look for in the s to seperate the stenacron and Macc? The only thing I can find in my book by Cormier and Knopp, is the shape of the gills.
Konchu on Mar 30, 2007March 30th, 2007, 3:12 pm EDT
Stenacron has the pointy gills
Stenonema & M. don't
That's what I use for starters
Stenonema & M. don't
That's what I use for starters
Troutnut on Mar 30, 2007March 30th, 2007, 3:16 pm EDT
I think that prominent black spot on the wing means it's Stenacron.
I have no clue how to tell one Stenacron species from another, but the one most commonly referenced is Stenacron interpunctatum, so that's as good a guess as any.
I have no clue how to tell one Stenacron species from another, but the one most commonly referenced is Stenacron interpunctatum, so that's as good a guess as any.
Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist
Troutnut and salmonid ecologist
CalebBoyle on Mar 30, 2007March 30th, 2007, 3:18 pm EDT
Cool, I didn't know about the black dot thing. It looks alot like your stenacron species Jason, except mine is a little more pink in the abdomen.
Konchu on Mar 31, 2007March 31st, 2007, 1:44 am EDT
The pink is probably the eggs.
GONZO on Mar 31, 2007March 31st, 2007, 6:53 am EDT
CalebBoyle-
Beautiful female dun--nice photos. The dark area in the third space on the wing (between R1 and R2) is usually a good character for distinguishing between Stenacron and Maccaffertium or Stenonema adults. It is expressed either as a black dot, as in your specimen, or, more commonly, as a dark patch that connects or nearly connects two or three crossveins.
Distinguishing the Stenacron species as adults is pretty tough and usually requires a male specimen (for penes differentiation) or rearing adults from identified larvae. This specimen lacks the dark spiracular marks (spiracles are the little breathing holes along the abdomen) and the dark streak below the wing base that one often sees on Stenacron interpunctatum. But, as far as I know, these may not be definitive characters.
Beautiful female dun--nice photos. The dark area in the third space on the wing (between R1 and R2) is usually a good character for distinguishing between Stenacron and Maccaffertium or Stenonema adults. It is expressed either as a black dot, as in your specimen, or, more commonly, as a dark patch that connects or nearly connects two or three crossveins.
Distinguishing the Stenacron species as adults is pretty tough and usually requires a male specimen (for penes differentiation) or rearing adults from identified larvae. This specimen lacks the dark spiracular marks (spiracles are the little breathing holes along the abdomen) and the dark streak below the wing base that one often sees on Stenacron interpunctatum. But, as far as I know, these may not be definitive characters.
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