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Montana Field Guide

Montana Field Guides

A Rhyacophilan Caddisfly - Rhyacophila oreia

Potential Species of Concern
Native Species

Global Rank: G1G3
State Rank: SU
(see State Rank Reason below)

Agency Status


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State Rank Reason (see State Rank above)
This Rhyacophilan Caddisfly is currently ranked a "SNR" a Potential Species of Concern in MT and at risk because of very limited and/or potentially declining population numbers, range and/or habitat, making it vulnerable to extirpation in the state. Limited sites with small populations, and the species is difficult to identify without adult specimens. Only 2 records for Montana
General Description
Rhyacophila oreia is a free-living caddisfly (no case) that is a regional endemic only known from a limited area in Wyoming, Idaho and now Motnana. Ecological data for U.S. states and Canadian provinces is known to be incomplete or has not been reviewed for this taxon. Although, given it's locality information for Montana, this species like others in the oreia species group, prefer small, fast-flowing cold forested streams.

Range Comments
Known from a limited areas in Montana, Wyoming and Idaho.

Observations in Montana Natural Heritage Program Database
Number of Observations: 2

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density



(Observations spanning multiple months or years are excluded from time charts)

This Rhyacophila seems restricted to spring-influenced cold-forested, streams in the forested streams of western Montana

Food Habits
Most Rhyacophila species are predators feeding mostly on aquatic insects, especially midges and blackflies

Limited data and the inability to identify larval collections has lead to a low global rank. Distribution data for U.S. states and Canadian provinces is known to be incomplete or has not been reviewed for this taxon.

Threats or Limiting Factors
Specific threats to Montana populations of R. oreia would include mismanagement of forested riparian areas, including sediment and temperature increases associated with road building and timber harvests not following BMPs. In general, cold-stenothermic (cold-water specialists) invertebrate populations are affected by changes to aquatic habitat, such as alteration of flow patterns, streambed substrate, thermal characteristics, and water quality. Alteration and degradation of riparian and aquatic habitat is the primary concern for Montana populations.

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Citation for data on this website:
A Rhyacophilan Caddisfly — Rhyacophila oreia.  Montana Field Guide.  .  Retrieved on , from