Length: 4 - 10 mm in tribe
Though the Wrinkled Bark Beetles were once accorded family status (Rhysodidae), they are now considered a tribe of Ground Beetles (Carabidae) in subfamily Scaritinae (Bell, 1998). The tribe includes about 375 species found worldwide.
These beetles are well-adapted for life under bark. The mentum is sharp, and allows the insect to move forward between layers of wood cells. Their route of passage closes back up after they pass, and thus they do not leave tunnels like many other wood-associated beetles. The mouthparts include stylets specialized for feeding on slime molds (Bell and Bell 2009).
Usefully for life under bark, the body of Wrinkled Bark Beetles are dorso-ventrally flattened. The beetles are elongate, and the pronotum is elongate as well. The antennomeres are monoliform (bead-like). The head bears two prominent temporal lobes, giving the beetle a bizarre appearance not found in other groups.
During the earliest days of insect classification Wrinkled Bark Beetles were assumed to be closely related to other kinds of bark beetles such as those in Cucujidae. However, characters of the wing veins, and of the legs of larvae, made it clear that the beetles were in Adephagathe large group that includes the aquatic beetles as well as ground beetles (Carabidae) (Bell 1999).
Photo data: 25 May 2020. Under bark. North Bend State Park, Ritchie County, West Virginia.