Abstract
The genus Gastrocentrum Gorham, 1876 is revised to include nine species. Five new species are described in this genus: G. magnum sp. nov. (NE India), G. regulare sp. nov. (Cameron Highlands, Malaysia), G. xiaodongi sp. nov. (Gyirong, Xizang, China), G. zayuense sp. nov. (Zayü, Xizang, China), and G. gaoligongense sp. nov. (Fugong, Yunnan, China). Gastrocentrum nitidum Schenkling, 1916 is transferred to the genus Tillus as a new combination. All the species in this genus are described (except G. brevicolle), and a key is provided for their identification. Illustrations of male genitalia, female reproductive organs, and other important structures are provided. An interspecific phylogeny-estimate of Gastrocentrum is presented based on morphological data, with two main clades recognized: a clade containing G. unicolor and G. laterimaculatum, and a clade containing the remaining six species (the latter a polytomy consisting of G. magnum sp. nov., G. dux, and G. regulare sp. nov., and a well-supported sub-clade representing the remaining species). Additionally, the taxonomic and phylogenetic importance of female reproductive organs is discussed.