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608-266-4340

Knobel's Riffle Beetle (Stenelmis knobeli)


Overview

Overview

Knobel's Riffle Beetle Stenelmis knobeli, a State Endangered beetle, is a black or gray cylindrical beetle often encrusted with sand or mineral deposits. Stenelmis knobeli has a sculptured pronotum, light markings on elytra, and filiform antennae. The adult measures 2.53-3.10 mm from anterior pronotum to tips of the elytra. Narrow, elongate elytra and weak sculpturing of the pronotum separates S. knobeli from the other 13 Stenelmis species in the state with similar elytral markings. This species has been found at three sites on the lower Wisconsin River in Richland County where the river habitat is large and warm with a shifting sand bottom. Adults have been found under or low on the sides of large sandstone rocks in riffles and runs. The species does best in habitat with constant water flow, little sediment, and moderate oxygen levels.

State status

Status and Natural Heritage Inventory documented occurrences in Wisconsin

The table below provides information about the protected status - both state and federal - and the rank (S and G Ranks) for Knobel's Riffle Beetle (Stenelmis knobeli). See the Working List Key for more information about abbreviations. Counties shaded blue have documented occurrences for this species in the Wisconsin Natural Heritage Inventory database. The map is provided as a general reference of where occurrences of this species meet NHI data standards and is not meant as a comprehensive map of all observations.

Note: Species recently added to the NHI Working List may temporarily have blank occurrence maps.


Documented locations of Stenelmis knobeli in the Natural Heritage Inventory Database as of July 2015.
Summary Information
State StatusEND
Federal Status in Wisconsinnone
State RankS1S2
Global RankG1G3
Tracked by NHIY
WWAP SGCN

Species guidance


Note: a species guidance document is not available at this time. Information below was compiled from publication PUB-ER-085-99 (now out-of-print).

Identification: Black or gray cylindrical aquatic riffle beetle often encrusted with sand or mineral deposits with a sculptured pronotum, light markings on elytra, and filiform antennae. The adult measures 2.53-3.10 mm. from anterior pronotum to tips of the elytra. Narrow, elongate elytra and weak sculpturing of the pronotum separates S. knobeli from the other 13 Stenelmis species in the state with similar elytral markings.

Habitat: The lower Wisconsin River where these beetles have been found is a large, warm river with a shifting sand bottom. Adults were found low on the sides or under large sandstone rocks in riffles and runs.

State Distribution: The species has been found at three sites on the lower Wisconsin River in Richland County.

Phenology: Both adult and larvae of this species are aquatic. Adult riffle beetles crawl among underwater plants or debris, feeding on algae, moss and other plant material.

Management Guidelines: Optimal riffle beetle habitat requires constant flow of water, little sediment and moderate oxygen.

Photos/Video

Photos


Knobel's Riffle Beetle

Photo © Kurt Schmude.


Last revised: Thursday, May 04, 2017