New species are described in the genera Wormaldia (Trichoptera, Philopotamidae) and Drusus (Trichoptera, Limnephilidae, Drusinae). Additionally, the larva of the new species Drusus crenophylax sp. n. is described, and a key provided to larval Drusus species of the bosnicus-group, in which the new species belongs. Observations on the threats to regional freshwater biodiversity and caddisfly endemism are discussed. The new species Wormaldia sarda sp. n. is an endemic of the Tyrrhenian island of Sardinia and differs most conspicuously from its congeners in the shape of segment X, which is trilobate in lateral view. The new species Drusus crenophylax sp. n. is a micro-endemic of the Western Balkans, and increases the end-emism rate of Balkan Drusinae to 79% of 39 species. Compared to other Western Balkan Drusus, males of the new species are morphologically most similar to D. discophorus Radovanovic and D. vernonensis Malicky, but differ in the shape of superior and intermediate appendages. The females of D. crenophylax sp. n. are most similar to those of D. vernonensis, but differ distinctly in the outline of segment X. Larvae of D. crenophylax sp. n. exhibit toothless mandibles, indicating a scraping-grazing feeding ecology.