This picture came out poorly, but it still shows pretty well just what effective tools those rear prolegs are for caddis larvae to grip the rocks. It can be surprisingly hard to pick them up when they're grabbing onto something.
Rhyacophila fuscula (Green Sedge) Caddisfly Larva from Mystery Creek #62 in New York
Troutnut.com is a collection of pictures and information about fly fishing. Fly fishermen, fly tiers, and trout enthusiasts of all stripes can learn more about life beneath the surface of trout streams, as well as how to better imitate aquatic insects with artificial flies to catch trout. There are aquatic insect pictures, underwater pictures, landscape pictures, and a comprehensive reference to the common names of trout stream insects.