Stenelmis douglasensis
Douglas stenelmis riffle beetle

Key Characteristics

A small aquatic beetle, this species has a pronotum (dorsal plate behind the head) and elytra (outer wing coverings) 0.09-0.16 inches (2.4 to 4.1 mm) long. The pattern of tubercles, sulci (narrow groves), costae (ridges) on the pronotum are also diagnostic (see technical manuals).

Status and Rank

  • State Status: SC
  • State Rank: S1S2
  • Global Rank: G1G3


County NameNumber of OccurrencesYear Last Observed
St. Joseph11933
Distribution map for Stenelmis douglasensis

Updated 5/15/2018. Information is summarized from MNFI's database of rare species and community occurrences. Data may not reflect true distribution since much of the state has not been thoroughly surveyed.


The Douglas riffle beetle inhabits large spring-fed lakes, river edges, and small streams with sandy bottoms, occupying shallow, clear, unpolluted water with high dissolved oxygen. It is often located on pieces of wood. This species is found only within a 150 mile radius of Lake Michigan in Michigan, Wisconsin, Illinois, and Indiana.

Specific Habitat Needs

Clear needed in Inland Lake, Littoral, Benthic Sandy substrate needed in Prairie fen, Floodplain forest, Headwater Stream (1st-2nd order), Riffle, Mainstem Stream (3rd-4th order), Riffle, River (5th-6th order), Riffle

Natural Community Types


For each species, lists of natural communities were derived from review of the nearly 6,500 element occurrences in the MNFI database, in addition to herbarium label data for some taxa. In most cases, at least one specimen record exists for each listed natural community. For certain taxa, especially poorly collected or extirpated species of prairie and savanna habitats, natural community lists were derived from inferences from collection sites and habitat preferences in immediately adjacent states (particularly Indiana and Illinois). Natural communities are not listed for those species documented only from altered or ruderal habitats in Michigan, especially for taxa that occur in a variety of habitats outside of the state.

Natural communities are not listed in order of frequency of occurrence, but are rather derived from the full set of natural communities, organized by Ecological Group. In many cases, the general habitat descriptions should provide greater clarity and direction to the surveyor. In future versions of the Rare Species Explorer, we hope to incorporate natural community fidelity ranks for each taxon.


Primarily threatened by degradation of stream habitat, especially that which alters shorelines, causes siltation, or lowers dissolved oxygen. Maintain a forested buffer zone around streams, avoid any hydrologic alterations.

Survey Methods

Ideal survey period unknown, but likely similar to other riffle beetles in mid to late summer. To survey, examine small (30 cm) to large (log size) pieces of wood along 30 m to 50 m of suitable stream reaches or shorelines at depths of 0.25 m to 1.5 m.

Page Citation

Michigan Natural Features Inventory. 2007. Rare Species Explorer (Web Application). Available online at [Accessed Sep 23, 2018]


Survey References

Technical References

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