Re: Book on Hatches.
Kytroutbum is correct, I didn't mean to come across like a know it all. I'm just hoping that you don't get intimidated by basic bug identification. It will help a great deal when you fish. Another hint: Most of the time when you first see a hatch and they don't take your dun's (adult dry's) they are really keying in on the emergers. Use a true emerger in the film or a nymph unweighted and you will catch fish. As for Sulphurs and Little Yellow stones. Not to confues anyone but most people call a lot of different Adult Drys that are somewhat whitish/yellow bodied for Sulphurs.
Light Cahill, , Pale Morning Dun in the West/ Pale Evening Dun in the east and even Light Hendrickson are all basically grouped as Sulphurs along with the real Sulphurs Ephemerella invaria and Ephemerella Dorothea are Sulphur Dun and Little Sulphur Dun respectively. It is fun to study all these but if you see a yellow fly that you have identified as a mayfly I would use either imitation, Light Cahill, PMD/PED or a Hendrickson. On tailwaters and out West you must be more exact in your identification but here in the smokies all you need to know is the color/size/ and if it's a mayfly. If it is a Stonefly it is probably a Little Yellow Stone Fly and I would use a fly called Yellow Sally. I believe we don't have true Yellow Sallies here in the east but more in the west but we call the Little Yellow Stones by that name. Confusing I know. In short: Learn to identify if it is a yellow colored mayfly or a stone fly or perhaps a caddis, all appear in the smokies. If the hatch you saw in late July was sporadic and happened throughout the day I will tend to guess Yellow Stone. It is possible that it was Light Cahill but that is a little late for them and they don't produce very thick hatches. The Little Yellow Stone appears troughout the afternoon/evening and it can be thick. I do believe there are Yellow Drakes at lower elevations in the park and if it was close to dusk it could be. You would notice if it is a drake they are very large size mayflies about a 10 or 12. Hope this helps.