One would think emergers would either have raised "fuzzy" ribbing or be smooth bodied.....
However, folks imitate them both ways.
If you wrap a turkey or goose biot with the shiny side out, you get a raised, "fuzzy" ribbed body.
If you wrap with the dull side out, you get a smooth, but ribbed, body.
Which do you think most closely resembles the emerging mayfly. I'm not talking about a swimming nymph. I'm talking about an emerger at the surface, but not yet an escaped dun.