My favorite pupal imitation is Al’s Rat..
Pupa float to the surface slowly, bodies moving feeblely in a swimming motion.
When they reach the meniscus (surface film) they
hang vertically in the film, struggle out of the pupal Shuck and fly away...
Trout sip them in, leaving only a tiny dimple at the surface.(dimpling rise)
Imitate this activity by-dressing your leader to within 6" of the fly to present your imitation just below the surface film.