Taxonomic notes on the genus Hexanchorus Sharp, 1882 and Heterelmis Sharp, 1882 from Bolivia (Coleoptera, Elmidae)

The genus Hexanchorus Sharp, 1882 is represented in Bolivia by one species, H. tibialis Hinton, 1935. A series of this species was originally collected by Germain in the Yungas of Cochabamba and, in 1935, described by Hinton based on a single specimen that is in poor condition and lacks several key characters. Here, we redescribe H. tibialis based on additional material collected by Germain and describe a new species, H. siriono sp. nov., from Santa Cruz, Bolivia, which exhibits striking male sexual dimorphism in the protarsi. Both species are illustrated with photographs of the habitus and drawings of the male genitalia, and for H. siriono sp. nov. also the female genitalia. Germain's journey in Bolivia and its known elmid fauna are briefly discussed. Additionally, Helmis cervina Grouvelle, 1896 and Helmis longior Grouvelle, 1896, both from Bolivia, are formally transferred to Heterelmis Sharp, 1882. The lectotype of the latter species is designated.