The squirmy wormy is a fly pattern that originated in the USA and is based on a relatively new material consisting of an incredibly stretchy rubbery substance.
The material is available in a four colours and wiggles just like the real thing. You'll struggle to find a worm imitation anywhere near as lifelike or effective as the squirmy. Very generous amount in these packets.
Brown, Orange, San Juan Red and Pink
See how to tie with Squirmy Worm here