Hopper patterns work in late summer because grasshoppers fall in the water. Wind blows them off bankside grass; storms wash them out of meadows. A trout that's been sipping midges all summer will hold its lane on a hopper because the calories are worth the risk.
Modern hoppers are mostly foam — a foam body shaped to a hopper silhouette, rubber legs, a bullethead, sometimes a parachute hackle for visibility. Tan, yellow, and pink-bellied are the standards. Fly shops carry a dozen named variations (Morrish Hopper, Fat Albert, Schroeder's Para-Hopper); they all work.
Fish it cast tight to a grassy bank, with an audible "plop" — a real hopper hits the water hard. Let it sit for a beat, then twitch the rubber legs once. Most strikes happen in the first three seconds after landing.