Heterlimnius
Guides
Optioservus
Optioservus is a former genus of riffle beetles (family Elmidae) established by Sanderson in 1954. As of 2021, it is recognized as a junior synonym of Heterlimnius. The genus formerly contained approximately 13 species distributed in the Nearctic region, including several species described by White in 1978. Species-level identification historically relied on variable external characters; a 1978 revision established more reliable diagnostic criteria based on male genitalia, elytral patterns, and geographic distribution.
Promoresia tardella
Promoresia tardella is a species of riffle beetle in the family Elmidae, originally described by Fall in 1925. The species has undergone taxonomic reclassification, with modern sources treating it as a synonym of Optioservus tardellus. It has been recorded from North America, specifically from Vermont in the United States. As an elmid beetle, it likely inhabits freshwater environments, though specific ecological details remain poorly documented.