Maturity and Mystery: Insects from the Doyles River at Blufton Road

Just when I think that the Baetis intercalaris small minnow mayflies are just beginning to show up in our streams -- and to date, I have only seen young ones -- I find something like this: a beautiful, colorful, fairly mature B. intercalaris nymph!  Compare this to one of the two that I found yesterday at the Powells:

I guess the lesson learned is that these nymphs are in our streams for a long stretch of time.  And although the "main" B. intercalaris hatch occurs here in late summer and fall, we still find some "early birds" that are already mature in May and June.  Whatever the answer, this was a beautiful nymph to find in the Doyles.

But this is only one of four mature insects that I found today.  Obviously, lots of things are getting ready to hatch.  The other three?

1) Common stonefly: genus Perlesta

2) Small minnow mayfly: species, Plauditus dubius (female)

and 3) Flatheaded mayfly: genus Leucrocuta

And there was one other species of small minnow mayfly, not yet mature -- Baetis pluto.

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And now for the "problem child," or, possibly, "problem children."  I found two, very small, flatheaded mayflies that I am, at this point, hesitant to identify to the level of species.  These:

Now, they are clearly Epeorus nymphs in terms of the genus: only two caudal filaments (tails).  And, they appear to be the same species, given the pale/yellow spots on tergites 1 and 2.  Given the 4 irregular pale spots on the leading edge of the head, I'd conclude that they are E. vitreus nymphs.  But, have another look at the two.  First, the one at the top of the photo, the one with the broken tail (nymph 1).

And then nymph 2.

Look closely at the shapes of the heads (fairly rectangular vs. fairly round) and the shapes of the eyes: not exactly the same.  The gills seem to differ as well.  And have a close look at the head of nymph # 1.

It's not only "subquadrate" in shape, there are lateral indentations, and the back edges of the eyes project behind the back edge of the head.

Hmm....   Well, I've got some work to do.  These may turn out to be "variations" on the E. vitreus theme. If not, I'll let you know.  Always like a mystery!
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The Doyles River below the bridge at Blufton Road.

And the photographer hard at work on Father's Day!  (Not easy on the elbows and knees.)