Calopogon orchid petal shapes

Recently, I was asked by someone for the best way to identify the four species of Calopogon (Grass-pink orchid) species that we have in the Southeast. This is a figure that appears in my book, Wild Orchids of South Carolina, and it can be used to easily identify the different species of Grass-pink orchids that you may encounter. This is a picture of actual petals from these orchids showing their shape and relative size. Hope this helps.