The Humpy is the dry fly you tie on when you want something a trout can see and you can't keep a finer pattern afloat. The signature feature is a hump of deer or elk hair pulled over the back to trap air - that buoyancy lets it ride high through riffles, pocket water, and broken current that would drown a parachute. It imitates nothing in particular; the chunky silhouette just reads as a meal.
Sizes 10-16 cover most water. Yellow is the everyday default and the closest thing to a caddis or yellow sally. The Royal Humpy, with its red floss body banded in peacock herl and a white calf-tail wing, is the most visible in fast water - tie it on when you're losing track of your fly in glare or chop. Red is the third common variant when you want a different attractor look.
Fish it as a high-floating searching pattern in normal to high water, clear or stained, when water temps sit in the 48-65F window and trout are looking up. Dead-drift it through seams and pockets, and lean on it as the dry in a hopper-dropper - it floats well enough to suspend a beadhead nymph below.