I take all the guessing out of the game and save a lot of money by just putting a drop of superglue on a #16 and holding the live bug there until it sets. Works anywhere. I do pinch the barb in C&R sections.
As sagefisher says, there are so many bug variations there are literally hundreds of books alone on the thousands of water flies out there. Identifying them is a game for the entomologist like Hodgkins on Bones to even begin to narrow down the fields. People who can even zero in on local generalizations simply amaze me.