The caddisfly Drusus dudor Oláh, 2017 (Limephilidae: Drusinae) was described from the Northwestern Italian Alps. We provide a detailed description of the larva, based on material from the Italian Province of Piemonte. Information on the morphology of the 5^th larval instar is given, and the most important diagnostic features are illustrated. The larva is included in an updated key to larval Drusinae where D. dudor keys together with Drusus aprutiensis Moretti, 1981, D. camerinus Moretti, 1981, D. croaticus Marinkovic-Gospodnetic, 1971, D. mixtus (Pictet, 1834), and D. nigrescens Meyer-Duer, 1875. The species can be reliably separated by the morphology of the pronotum, the shape of the metanotal sclerites, and by morphological details of abdominal sternum I.