The state of Wyoming contains the headwaters for the Missouri, Columbia, and Colorado River Basins. These rivers provide habitat for about 59 species of fish. These rivers are also home to thousands of species of aquatic invertebrates. 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.