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Coleoptera of Great Smoky Mountains National Park Species Pages

Family Nosodendridae

 Nosodendron unicolor Say

The slime flux beetle

Description and Taxonomy

Description. Adult length 5-6mm; mature larvae 6-8mm.  This black, oval beetle bears a superficial resemblance to certain nitidulids and dermestid beetles, but differs in many details. The presence of deep cavities where the antennae can be concealed along the anterior angles of the prosternum, fully retractable legs, and distinctive and uniform shape of the body will distinguish these beetles from members of other families. The larva is more distinctive in appearance than the adult. The sclerotized, cone-shaped 8th abdominal segment and lateral setose processes along the body make it unlikely to be confused with any other beetle larva.

Nosodendron contains 58 described species worldwide, but this is the only member of the family in the eastern U.S. Two more occur in the west, N. californicum Horn and Orphilus ater Erichson, though placement of the latter species in Nosodendridae instead of Dermestidae is contentious. The family has a colorful taxonomic history (Ivie 2002).

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. Specimens are difficult to see in the wet, black fluid substrate, but can usually be found by carefully scraping away layers of fluid and bark onto a white surface and inspecting it. Slime fluxes are diverse habitats containing yeasts, bacteria, and fungi that subsist directly on fluids produced from the tree, generating products of fermentation in the process. The microorganisms in turn serve as food for larger organisms, including nosodendrids and members of various other beetle famililies (e.g., Nitidulidae).

Distribution

Nosodendron unicolor is widely distributed across eastern U.S. and southern Canada, from Ontario and Wisconsin to Florida and Texas. In GSMNP it is known from only a few localities where known slime fluxes occur. The species can be expected throughout the Park with additional investigations of these habitats.

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. 

Mature larva, N. unicolor.

 

Collecting N. unicolor in deciduous slime flux (photo, A. R. Cline).

 

Exposed larva of N. unicolor in slime flux.

Locality records in GSMNP.

 

Acknowledgements

Development of these pages was supported by grants from Discover Life in America and the National Science Foundation (DEB-0516311).

References

Ivie, M. A. 2002. Nosodendridae. pp. 224-227  in R. H. Arnett, Jr., M. C. Thomas, P. E. Skelley, and J. H. Frank (eds.). American Beetles, Vol. 2. CRC Press, New York, NY.

Posted 17 October 2006, C. E. Carlton, Louisiana State Arthropod Museum. Habitat photo, A. R. Cline.

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