A "variant form" of Isoperla orata

Nymph #1, Isoperla orata

Nymph #2, Isoperla orata, variant form

When he first saw nymph #2 two years ago, Beaty felt that it wasn't the same as nymph #1.  After close study, at the moment he feels that they might be the same -- Isoperla orata -- with nymph 2 being a variant form.  Nymph #1 was tagged as Isoperla orata some time ago (T. H. Frison, Studies of North American Plecoptera, 1942, --. 323-325).  Given the different patterns we see on nymph #2 (both head and abdominal patterns, see the entry of 5/15), it would have to be a variant form.

Beaty admits that we can't be sure of the ID of nymph #2 until someone rears it and we see the adult. In the meantime,  I'll simply call it "Isoperla orata vf."  (vf for variant form).

I have nagging doubts.  Isoperla orata vf. is a stonefly that I've found in three, quite different streams: the Upper Doyles River, Buck Mt. Creek, and the Rapidan River.  The Rapidan River is the only place I've seen I. orata.  And, when I was up there last week, I. orata vf. nymphs were a dime a dozen, I only saw one I. orata.   In fact, in four years of looking, I've only found four I. oratas.  There are differences that must be explained.
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Upper Doyles River (in winter)

Buck Mt. Creek

Rapidan River