Some fly fishermen still think of the unpopular 'worm angler' when seeing patterns like that. Although the use of worms is present especially in the stillwater fishery for a long time now. And also on running waters worms (like the 'Vladi Worm' or 'San Juan Worm') are important in special situations: When the river is high and the banks flooded worms become an attractive food source for trout and grayling. In muddy/brown water their silhouette and movements are still able to seduce the fish. A great alternative to streamers!
The Squirm Worm/Widdly Worm is the latest step in the evolution of worm patterns. Here, it's tied with elastic silicon on the brilliant Tiemco 2499SP barbless hook. A tungsten bead helps to present the fly effectively in faster currents too.
Tipp: When fishing on a lake use it in combination with a regular indicator or a Bung fly. On the river try to present it like a nymph in dead drift. If that technique doesn't work, lift and lower your rod tip to add extra action to the fly. Best suited are long rods (10ft. - 11ft.) with a sensitive tip (#3 or #4) and the special nymph leaders by Soldarini.