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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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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PaulRoberts on May 4, 2012May 4th, 2012, 7:54 am EDT
Any guesses as to who this is? It's a pretty good sized "golden stone" although it's not very golden -a pale translucent underside and mostly the dorsum mostly in browns. I'd tie it in a size 10 3xl.
Entoman on May 4, 2012May 4th, 2012, 7:25 pm EDT
I don't recognize the head capsule pattern off the top of my head, but it sure looks like a perlodid to me Paul, either a Springfly or Stripetail. A few answered questions might help us nail down the genus. Did it have thoracic gills? How about longitudinal abdominal striping (can be very feint). If we can get the choices down to a couple of genera, I'll look though what I've got to see if I can come up with a head match. Your specimen looks pretty distinctive.
"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
PaulRoberts on May 5, 2012May 5th, 2012, 4:30 pm EDT
No striping. There were some striped (Isoperlid?) guys there. I didn't think to look at gills. If there were, they were small and not visible from the topside (only images I have). Didn't expect to post this originally.
Entoman on May 5, 2012May 5th, 2012, 11:28 pm EDT
Well, your answers don't make it as easy as hoped.:) If it had gills they would be small and finger-like or even bumps emanating from the thoracic joints behind the legs and perhaps even from the cervical joint. FWIW I'm not seeing any evidence of them in the photo, though it must be conceded that reliable determinations are much easier if the critter is held upside down for a good close-up of the thorax and head. What to look for are the presence of gills and a good look at the mouth parts and mesosternum.
Assuming a lack of gills, of the five genera lacking this character known for CO, four are represented by single species. Of these four, Cultus is too small and Diura, Arcynopteryx and Skwala look different both in pattern and conformation (wing pad shape, legs, etc.).
While the remaining genus usually has stripes, their absence is not as diagnostic as once thought and the thick narrow cervix, shape of the wingpads, and antennae length sure look right. I'm thinking Isoperla and will start looking there for a head capsule match. Hopefully one exists, though there are at least 11 species reported from CO and to my knowledge many have never been photographed.
Assuming a lack of gills, of the five genera lacking this character known for CO, four are represented by single species. Of these four, Cultus is too small and Diura, Arcynopteryx and Skwala look different both in pattern and conformation (wing pad shape, legs, etc.).
While the remaining genus usually has stripes, their absence is not as diagnostic as once thought and the thick narrow cervix, shape of the wingpads, and antennae length sure look right. I'm thinking Isoperla and will start looking there for a head capsule match. Hopefully one exists, though there are at least 11 species reported from CO and to my knowledge many have never been photographed.
"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
PaulRoberts on May 6, 2012May 6th, 2012, 7:46 am EDT
I'll photo both sides next time.
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