Acneus beeri
Hatch, 1961
Beer's false water penny beetle
Acneus beeri is a of aquatic in the Psephenidae, known from a single female specimen collected east of Cascadia, Oregon in July 1940. The species belongs to the false water penny beetles, a group characterized by their flattened, oval body form adapted for clinging to submerged surfaces in flowing water. No additional specimens have been reported in the more than 80 years since its original description, making it one of the most poorly known North American beetle species.
Pronunciation
How to pronounce Acneus beeri: /ˈæknɛəs ˈbɪəri/
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Identification
No reliable identification characters have been established beyond the original . The cannot be distinguished from or related psephenid beetles without direct comparison to the . Identification of Acneus species generally requires examination of male genitalia and subtle differences in elytral , neither of which are available for A. beeri.
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Appearance
The original description was based on a single female specimen. As with other Psephenidae, the likely exhibits the 's characteristic strongly flattened, broadly oval body form with a smooth, shield-like surface. of related species typically have short and legs positioned laterally for clinging to substrates. Specific coloration, size measurements, and remain undocumented due to the lack of additional specimens.
Habitat
The type locality east of Cascadia, Oregon suggests association with lotic (flowing water) environments, as is typical for the Psephenidae. Members of this family are generally found clinging to rocks, wood, or other submerged substrates in streams and rivers. Specific microhabitat preferences for A. beeri remain unknown.
Distribution
Known only from the type locality east of Cascadia, Linn County, Oregon, USA. No additional records exist.
Seasonality
The was collected in July 1940, suggesting summer activity. No information on patterns or larval is available.
Similar Taxa
- Other Acneus speciesCongeneric share the flattened body form and aquatic ; A. beeri was distinguished in the original description by subtle morphological features now difficult to assess without type comparison
- Psephenus speciesTrue water penny beetles in the related Psephenus occupy similar and share the characteristic disc-like body form; they differ in details of antennal structure and larval
More Details
Conservation status
The is effectively a data deficient . The absence of records since 1940 may reflect genuine rarity, loss, or taxonomic obscurity rather than extinction. The Willamette Valley region of Oregon has experienced substantial anthropogenic modification of stream habitats since the 1940s.
Taxonomic history
Described by Melville H. Hatch in 1961 based on a specimen collected by M. Beer in 1940. The specific epithet honors the collector. The Acneus is one of several psephenid genera with limited and restricted distributions in western North America.