Biology and identification resources for Hydrochus spangleri Hellman, an endangered aquatic beetle from the Delmarva Peninsula (Coleoptera: Hydrophilidae)

The Seth Forest water scavenger beetle (Hydrochus spangleri Hellman) is endemic to the Delmarva Peninsula and listed as endangered by the states of Delaware and Maryland. This species is restricted to forested vernal ponds in the coastal plain. The identification of this species, particularly females, can be difficult as species of Hydrochus are morphologically very similar. Here we present new data about the distribution and biology of H. spangleri as well as molecular characterization of the species using cytochrome oxidase I mtDNA (ie., DNA barcoding). A revised illustrated key to the Hydrochus of the Delmarva region is provided.