This common name refers to only one family.
These are sometimes called Microcaddisflies.
Both anglers and entomologists know these diminutive flies as "Microcaddisflies." The term refers to this family specifically, not to all tiny caddisflies. Many are large enough for imitation on small hooks, but some are impossibly small, as tiny as hook size 36.
Like the Tricorythodes
mayflies, Microcaddisflies can be important to trout because of their extreme abundance in certian waters.