Flattened Clown Beetles: these beetles have remarkably thin, flat bodies that can slide beneath the bark of dead and dying trees
Above: Hololepta plana and Hololepta aequalis
Beetles of the genus Hololepta are often referred to as flat clown beetles, due to their wafer-thin bodies and the "clown-shoe" shape of their feet. They measure roughly 8-10mm long, but their bodies have a thickness of just 1mm, which is about as thick as a credit card; this peculiar morphology allows them to crawl beneath the bark of dead or dying trees, where they feed on the larvae of other arthropods.
Above: Hololepta aequalis
As this book explains:
The flat clown beetle is profoundly flattened—the depth of the body is approximately one-tenth its total length. The legs are pressed against the body for effective pushing, and the mandibles extend far forward to allow the beetle to capture prey in narrow spaces. The entire body is strongly armored, a feature shared by other members of the Histeridae.
Above: Hololepta plana
The name of the genus Hololepta is derived from the Greek words hólos and leptós, meaning "completely thin." Most of the beetles in this genus have flat, rectangular bodies, large mandibles, and shiny black exoskeletons.
Above: Hololepta species
These beetles often carry phoretic mites, which have tiny, globular bodies with a reddish-brown or pink appearance.
Above: phoretic mites hitching a ride on some flat clown beetles
Sources & More Info:
The Book of Beetles: Flat Clown Beetle
The Museum of Natural History at the University of Oxford: A Family of Clown Beetles
iNaturalist: Genus Hololepta
A Color Guide to Beetles: Hololepta plana
Beetles of Eastern North America: Hololepta aequalis
Beetles of the World: a Natural History: Clown or Hister Beetles
