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.
Costal projection: A bump or point sticking up from the front margin of an insect's wing, usually the rear wing of certain mayflies. It is sometimes called a costal process.
This other word references the same concept: costal projections.
