Olive Caddis is an evening event from late spring through early fall, peaking in June and July when water temps sit in the 54-65F window. Unlike a mayfly that rides the surface, a caddis hatch happens fast: the pupa rockets up through the water column, the adult breaks free of the pupal skin near the top, and it flies off almost immediately. That speed is why trout often take the rising pupa harder than the dry.
Watch for a splashy, aggressive rise in the last hour of light - that boil is a fish chasing pupae, not sipping. If the rises are slashing and you keep missing on a dead-drifted dry, you are fishing the wrong stage.
Run a soft-hackle caddis or a sparkle pupa just under the film, swung or twitched on the rise. When fish are eating adults off the top, an elk-hair caddis or X-caddis in olive, size 14-18, covers it. Fish the dry drag-free, then give it a twitch at the end of the drift - the skitter triggers strikes the same way a real egg-layer does.