Translucent

For aquatic insects that emerge in the surface film the partly shed cuticle (shuck) becomes an important consideration in fly design. As the adult works its way out of the cuticle the trailing shuck takes on a semitransparent, translucent look. When viewed from below, sunlight reflects and refracts off the thin shed cuticle and associated air bubbles, giving the trailing shuck a slightly glittery appearance. 

When tying emerger patterns the best way to imitate the trailing shuck is to tie in a tail of sparkly material. A few of strands of Krystal Flash or Antron yarn will usually do the trick. But remember to keep the tail sparse - it's easy to over do it.

Shed cuticles from Midge pupae (Chironomidae) viewed from above.

Shed cuticles from Midge pupae (Chironomidae) viewed from below. Note the air bubbles within each shuck.

Shed BWO cuticle (Baetis) viewed from below.