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Montana Field Guide

Montana Field Guides

A Mayfly - Tricorythodes explicatus
Other Names:  Tricorythodes minutus

Native Species

Global Rank: G5
State Rank: SNR
(see State Rank Reason below)

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State Rank Reason (see State Rank above)
Widespread throughout the state, tolerant of silt and warmer temperatures
General Description
This is a very widespread and tolerant mayfly species with triangular operculate gills on the second abdominal segment. Large hatches of this prolific mayfly ("tricos") can be seen in the silted sections of the Missouri, Yellowstone and Clark Fork River Basins. In fact all major river systems provide habitat for this ubiquitous mayfly if silted pool areas provide habitat. This species of mayfly increases in abundance when streams become silted, dewatered and warmer.

Observations in Montana Natural Heritage Program Database
Number of Observations: 361

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Relative Density



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

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