I've been in touch with Steven Beaty (NC DWQ), and he thinks that the Isoperla namata nymphs that I'm finding in Central Virginia should still, at the moment, be called Isoperla nr. namata. According to Beaty, the leading authority on Isoperla argues that true Isoperla namata is only found in the Ozarks and the Midwest. Also, Isoperla "patterns" can vary. So the three head patterns we saw yesterday still qualify as Isoperla nr. namata.
Those patterns were:
1. The most common, where the dark lines/bands from the transverse band crossing the head extend back to the lateral ocelii and beyond, to dark spots at the back of the head.
2. Nymphs where there are no lines extending from the transverse band back to the ocelli.
So, Isoperla nr. namata it will be. However, I think it's still worth our while to keep track of the streams in which we find each of these patterns. There may be habitat differences that account for these variations.