Nosodendron unicolor

Size
5.0-5.7 mm
Habitat
adults and larvae in actively flowing fluxes slime fluxes or tree wounds, or under bits of wet bark and debris along the margins of flows
Food
Dependent on microorganism-rich fermenting sap flows, which are more frequent and last longer on older trees than on vigorously growing young trees.
(https://bugguide.net/node/view/101363)

Life History
These strange beetles specialize on microorganism-rich fermenting sap flows, also referred to as slime fluxes or tree wounds, on deciduous trees. Both adults and larvae may be found in actively flowing fluxes completely or partially submerged, or under bits of wet bark and debris along the margins of flows.

Conservation Concerns
Despite its widespread distribution, the fact that N. unicolor is dependent on deciduous slime fluxes suggests it may be sensitive to landscape scale changes in forest composition. Slime fluxes are more frequent and last longer on older trees than on vigorously growing young trees, and often form in response to attack by wood boring insects such as cerambycid beetles and cossid moths. Anecdotal data suggest that the species is more common in GSMNP than elsewhere, perhaps because more overmature trees provide optimal conditions for populations to develop and persist.

(http://www.lsuinsects.org/research/speciespages/Nosodendridae/Nosodendron_unicolor.htm)