We coin the term "taxon expeditions" for citizen scientists' field courses to carry out publishable taxonomic work in close association with trained taxonomists. During the first-ever taxon expedition, in Maliau Basin Studies Centre, Sabah, Malaysian Borneo, the participants sampled leaf litter beetles from lowland dipterocarp forest using the Winkler apparatus. The collected material proved to contain at least three undescribed species of small-bodied (ca. 1 mm long) hemispherical litter-dwelling Coleoptera. As part of the field course work, taxonomic descriptions were prepared for the chrysomelid Clavicornaltica sabahensis sp. n. and the leiodids Colenisia chungi sp. n. and Dermatohomoeus maliauensis sp. n.