In a recent 3-gene phylogeny of the Trichoptera subfamily Drusinae Banks, 1916 molecular data clearly correlated with the morphology and feeding ecology of larvae. The largest of three main groups, the Drusinae grazer clade, exhibits an unusual larval feeding ecology for Limnephilidae, and is the most diverse group. In this paper we describe four previously unknown Drusinae larvae from this clade: Drusus balcanicus Kumanski, 1973 (micro-endemic to Eastern Balkans); Drusus botosaneanui Kumanski, 1968 (Dinaric Western Balkans, Hellenic and Eastern Balkan, Asia Minor), Drusus serbicus Marinković-Gospodnetić, 1971a (micro-endemic to Dinaric Western Balkans); and Drusus tenellus (Klapálek, 1898) (Carpathians, Dinaric Eastern Balkans). Characteristically, the larvae of these species develop toothless mandibles typical for the Drusinae grazer clade. Larvae and adults were unambiguously associated by a phylogenetic approach based on two mitochondrial (mtCOI, mtLSU= 16S rDNA) and two nuclear genes (nuWG, nuCAD). In addition, information on the morphology of the larvae is given and the diagnostic features necessary for identification are illustrated.

Keywords: 5th instar larvae; Drusus balcanicus; Drusus botosaneanui; Drusus serbicus; Drusus tenellus; description; distribution; identification; phylogeny.