Plants and Animals

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

US Status: No Status/Not Listed
State Status: SC - Special Concern (rare or uncertain; not legally protected)
Global Rank: G1G3
State Rank: S1S2 - Rank is uncertain, ranging from critically imperiled to imperiled


CountyNumber of OccurrencesYear Last Observed
Benzie 2 1990
Branch 1 1971
Calhoun 1 1971
Cheboygan 2 1945
Emmet 2 1952
Kalamazoo 2 1974
Lake 1 1934
St. Joseph 1 1933

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 water needed in: Inland lake, littoral, benthic; 

Sandy substrate needed in: Floodplain forest; Headwater stream (1st-2nd order), riffle; Mainstem stream (3rd-4th order), riffle; Prairie fen; River (5th-6th order), riffle; 

Natural Community Types

  • Floodplain forest
  • Headwater stream (1st-2nd order), riffle
  • Inland lake, littoral, benthic
  • Mainstem stream (3rd-4th order), riffle
  • Prairie fen
  • River (5th-6th order), riffle

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.

Management Recommendations

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.

D-frame net, dip net

Survey Period: From first week of April to first week of November

Time of Day: Daytime
Water Level: Low Water Levels
Water Turbidity: Low Turbidity
Survey Method Comment: Larvae

Visual surveys

Survey Period: From first week of June to fourth week of September

Survey Method Comment: Adults


Survey References

  • Martin, J.E.H. 1977. The Insects and Arachnids of Canada (Part 1): Collecting, preparing, and preserving insects, mites, and spiders. Publication 1643. Biosystematics Research Institute, Ottawa.
  • NatureServe. 2005. NatureServe Explorer: An online encyclopedia of life [web application]. Version 4.5. NatureServe, Arlington, Virginia. Available

Technical References

  • Merritt, R.W. and K.W. Cummins. 1996. An introduction to the aquatic insects of North America, 3rd ed. Kendall/Hunt Publishing Company, Dubuque. 862pp.
  • NatureServe. 2005. NatureServe Explorer: An online encyclopedia of life [web application]. Version 4.5. NatureServe, Arlington, Virginia. Available