This one seems to lead to Couplet 35 of the Key to Genera of Perlodidae Nymphs and the genus Isoperla, but I'm skeptical that's correct based on the general look. I need to get it under the microscope to review several choices in the key, and it'll probably end up a different Perlodidae.
My friend Willy captured this early instar damselfly nymph and brought it to me for identification. It is more robust and stocky at this early stage than the spindly appearance of the later instars, and its appearance is less familiar.