Amazonopsis, an unusual new genus of riffle beetle from South America with two new species (Coleoptera, Elmidae, Elminae)

Abstract. Amazonopsisgen. n. is described to include A.theranyisp. n. from Peru, Venezuela and French Guiana, and A.camachoisp. n. from Venezuela. The descriptions are accompanied by figures illustrating the male and female habitus of A.theranyi, the male habitus of A.camachoi, and male genitalia of both species. Amazonopsistheranyi exhibits pronounced secondary sexual dimorphism which likewise may be a characteristic of the genus. Amazonopsis males have modified protarsal and mesotarsal claws, a pair of small spines on the anterior prosternum, and a pair of ventrally directed processes on the posterior metaventrite. Females of A.theranyi display a pair of unique, oval perforations in the cuticle of the pronotum and have unmodified claws; females of A.camachoi are unknown. Descriptions are furnished of the stream habitats and microhabitats where the study specimens were collected.