The Hydroptilidae are a large family of caddisflies (Trichoptera) with a worldwide distribution. They are commonly known as microcaddisflies or purse-case caddisflies, in reference to two characteristic traits of this family: Hydroptilidae are much smaller than other caddisflies, rarely exceeding 5 mm (0.20 in) in length. Their larvae do not build a protective case until the final instar of their growth. At that time however, they build a typically Purse-shaped case, either portable or stuck to the substrate, in which the larva finishes growth and pupates.