Diving Caddis Grey - Larva & Pupa. Simulating a Caddis as they are diving to the rocks on the river bed, the Grey Diving Caddis are very tasty treats for the hungry trout as they descend to the bottom of the river. This can be fished on a dead drift, or on a wet fly swing for optimal performance. The Grey Diving Caddis can provide fantastic results right at dusk when trout are out on the hunt for many a caddis fly.