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Genus Psephenus

Beetles Impressive in Whitewater - Psephenus herricki flat larva - Psephenus herricki Psephenidae - Psephenus falli Psephenus texanus - male - female Psephenus - Psephenus herricki water penny beetle - Psephenus falli Psephenidae - Psephenus herricki Psephenidae - Psephenus herricki
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Hexapoda (Hexapods)
Class Insecta (Insects)
Order Coleoptera (Beetles)
Suborder Polyphaga (Water, Rove, Scarab, Long-horned, Leaf and Snout Beetles)
No Taxon (Series Elateriformia)
Superfamily Byrrhoidea (Pill, Water and Toe-winged Beetles)
Family Psephenidae (Water Penny Beetles)
Subfamily Psepheninae
Genus Psephenus
Synonyms and other taxonomic changes
First described in 1844 by James Ellsworth De Kay as Fluvicola, although De Kay mistook the maxillary palps of the larval specimen he had for a second pair of antennae and assumed this was a genus of crustaceans. The name Fluvicola had already been used for other organisms, so it couldn't be used for these.
First described as a genus of insects by John Lawrence LeConte in 1853 as Eurypalpus, but the name had already been used for a genus of other organisms.
Psephenus first appeared in an 1853 publication by LeConte and Samuel Stehman Haldeman as a replacement for Eurypalpus. Haldeman's name was next to it, so he is considered the author- but LeConte apparently considered himself to be the author, instead. Although there was no other information included, this counts officially as the first publication of the name.
Explanation of Names
Greek, probably from psephenos(ψεφηνος) 'dark, obscure', but it's tempting to try to derive it from psephos (ψηφος) 'a small round worn stone, pebble'
There was no explanation of the name accompanying its publication, so we can only guess.
7 spp. in our area(1)
adult 4-6 mm
Larvae: Psephenus has abdominal gills, while Ectopria does not (D.S. Chandler's comments here)
e., so., & w. US(1)
The resemblance of the larvae to trilobites has been remarked on frequently- going back to the first published description by De Kay- but, aside from both being arthropods, they're not at all related.
Internet References
Natural History of New York, pt.1, v.6,p.53    De Kay's description of the genus.
Catalogue of the Described Coleoptera of the United States, p.34    First publication of the name Psephenus
Works Cited
1.American Beetles, Volume II: Polyphaga: Scarabaeoidea through Curculionoidea
Arnett, R.H., Jr., M. C. Thomas, P. E. Skelley and J. H. Frank. (eds.). 2002. CRC Press LLC, Boca Raton, FL.