Start black 8/0 on a scud hook and tie in medium opal tinsel at the rear.
Dub a body of Canadian Olive Simi Seal forward, leaving the front third clear.
Rib the opal tinsel forward in open spirals, tie off and trim. The opal spark reads as the gas bubble a caddis pupa carries as it rises.
Spin a dubbing loop of chocolate brown Ice Dub and take two wraps for a thorax, then brush everything back. Brown against olive gives the fly the dark head a pupa shows.
Tie in a hen saddle feather, preen the fibres back, and take two or three wraps only. Two or three is deliberate. A sparse soft hackle swims, a dense one just sits there.
Tie off the stem, trim, whip finish, and dab glue or resin on the head. Lots of movement and a little flash, which is exactly what the trout want on a rising pupa.