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A Publication of the University of Wyoming's Biodiversity Institute


Wyoming is home to unique and spectacular rivers. Our state contains the headwaters for the Missouri, Columbia, and Colorado River Basins. These rivers provide habitat for about 59 species of fish. What is less known is that these rivers are also home to thousands of species of aquatic invertebrates. Many fish rely on aquatic invertebrates as the main component of their diet, for at least part of their lives. Birds, amphibians and mammals also eat insects that emerge from streams. Additionally, aquatic invertebrates are vital in controlling algal growth.

This guide will introduce you to the common invertebrates (mainly insects) living in Wyoming’s streams. The key will help you identify insects and other invertebrates to the major group that they belong to and you can flip to the appropriate section to identify the insects using the photos and characteristics provided. To help anglers, we also illustrate a few flies that imitate each insect order as well as adult emergence charts.

We hope you find the guide useful whether you are teaching, fishing, or learning more about Wyoming’s natural resources.

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