Selected Aquatic Insects of Oregon

Trout Unlimited and the River’s Calendar Project are initiating a pilot program in Oregon to track emergence dates of selected aquatic insects to assess if emergence periods are changing over time, possibly as a result of climate changes. The purpose of this field guide is to provide a quick identification aid to 15 common aquatic insects found in Oregon. These specific taxa were selected because they are well known insects found in Oregon’s streams and/or lakes and are frequently imitated by fly fishers. These species are also found outside of Oregon; other western anglers might find this guide helpful. To effectively document emergence dates, the insects being observed must be accurately identified. The hatches in this field guide consist of just one or two species and thus provide less confusion for species identification. By using this field guide anglers will be able to better determine if they are seeing one of these hatches on the water.

The fifteen insects selected consist of seven mayfly species, five stonefly species, and three caddisfly species. Information provided for each species consists of key identification characteristics of immature and adult stages as well as information on habitat, distribution, and emergence.

The emergence dates given are approximate and, when known, specific to the Metolius, McKenzie, Necanicum and Nehalem. One of the benefits of the River’s Calendar project is to improve our knowledge of emergence calendars on specific rivers, by collecting the observations of anglers who fish these and other streams. Anglers are welcome to join the River’s Calendar project, and help document emergence dates of these and other insects. Although the project is being tested on these streams and with these species, participation is not limited to either. If you witness hatches while you are fishing, your reports are of interest to this project. The River’s Calendar web site provides information on how to participate.

The production of this field guide was funded by Trout Unlimited.

Contribute your observations to the River's Calendar on iNaturalist: http://www.inaturalist.org/projects/the-river-s-calendar

Special thanks to Jack Williams and Darek Staab.
All photos by Rick Hafele except where noted less ↑