Correction: That's a female Plauditus dubius, not Iswaeon anoka

Sorry.  This is not I. anoka -- it's a female Plauditus dubius.  I was thrown off by its size.  As I noted this nymph is close to 5 mm; P. dubius nymphs tend to be smaller -- 3.0 - 3.5 mm.  But two things are off: 1) the median caudal filament on I. anoka is longer than segment 10: it looks like this.

That is not true for the nymph that I found today.  And 2) as noted in Beaty's description, there are "midventral dark spots ...present on abdominal sterna 2-8 or 9."  These.

There are no such marks on the nymph that I found today.  I can also note that the widening of the tibia from the base is more distinct on I. anoka than what we see on P. dubius.  It should look like this:

This is Iswaeon anoka, for which I will look in the Rivanna as soon as it clears.