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Montana Field Guide

Montana Field Guides

A Mayfly - Cercobrachys cree

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Native Species

Global Rank: G4
State Rank: SNR

Agency Status


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General Description
This is one of the most recently described mayflies occurring in the large prairie rivers of northern and eastern Montana (Milk and Powder Rivers) (Sun et al. 2002). Larvae were collected from the periphery of shifting sand bars and near shore. North Dakota, South Dakota and Saskatchewan represent eastern range limits (Guenther and McCafferty 2005 and 2008).

Range Comments
Montana has 24 occurrence records in the NHP database, all from the Milk and Powder Rivers.

Observations in Montana Natural Heritage Program Database
Number of Observations: 24

(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 species is associated with larger, perennially flowing prairie streams and rivers with sand-gravel dominated bottoms with cobble riffles. Larvae were collected from the periphery of shifting sand bars and near shore.

Threats or Limiting Factors
All forms of stream quality degradation pose potential threats. These include siltation; pollution from agricultural and industrial waste; and hydrological alteration from drainage, dams, or withdrawal of excess water for human use.

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Citation for data on this website:
A Mayfly — Cercobrachys cree.  Montana Field Guide.  .  Retrieved on , from