Imitates grasshoppers, which can be common from late July through early fall. Grasshoppers are terrestrial insects, but they often fall onto the water from streamside vegetation. They represent a large and easy meal to trout.
 
The Parachute Hopper rides lower in the water than other patterns, and trout often seem to prefer that.

Vary the body color to match the insects that are available.

Dress the fly with floatant and use standard dry fly presentations. On small streams, you can fish a hopper anywhere in the river, but on larger flows you will do best to present the fly right next to the bank. On larger rivers, the best places to cast are along the margins, no more than 15 feet from the bank, and often only inches from the bank. Unless you're fishing from a boat, you may find it works best to wade into the river and cast back to the bank.
 
One effective tactic is to cast so the fly hits shoreside grass, then lands in the river with a distinct plop. This mimics the natural insect. To further imitate natural behavior, give the fly an occasional twitch as it drifts.