The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large brown trout that only touch streamers for the rest of the year.
Caddisfly larvae of this family can easily leave and re-enters their cases. I caught two of them playing musical chairs or something with this one... funny!
This is one of the earliest videos I made, and I was experimenting with a tank and background that didn't work very well.
Water boatmen are excellent swimmers, and you can see here how they use their oars to push themselves through the water, a motion easily imitated by the fly fisher.