Download the Emergence Charts and/or Practical Keys PDFs
Clicking the link will take you to the releases page. Click on the word “Assets”, (if necessary) then click on the one or both of the zips. Once a zip arrives on your machine, move it to a suitable location and double click the file to unzip it.
Spatio-Temporal Emergence Charts
Trying to comprehend the large array of aquatic insects that make up much of a trout’s diet is a daunting undertaking. However, there are a number of generalizations and commonalities that go a long way toward making the task possible. These have been stated and exploited over the last several decades by a number of very perceptive authors. The charts presented here give a visual summary of these organizing principles, making them memorable as a whole and accessible in detail.
The novel element in the charts is that, in addition to the usual horizontal progression of the seasons, there is, for each bug type, a vertical progression of water types, from rather sterile headwaters near the top to fertile, mature rivers below.
These particular charts include only the mayflies and caddisflies, and are somewhat localized to the waters of California and the Pacific Northwest, but with modest seasonal adjustments, keeping in mind water type, and adjusting for local species, they readily adapt to any trout waters and other bugs.
In addition to the charts themselves, there is supporting material that expands and puts into context the very condensed information on the charts. All this comes in two forms: a zipped PDF that contains everything in one place, and a number of .md files (readable and writable in any text editor) that contain the explanitory text, and four .svg files (editable in Inkscape or Adobe Illustrator, for example) that contain the graphical charts themselves as well as the classification trees of the bugs. The .svg files (scalable vector graphics) have the desirable property that they print perfectly at any scale. The PDF may be downloaded from the release page for this repository (see link at the top of this page). All the other files reside in the repository itself. They can be downloaded all at once in zipped form from the release page, or visited by pressing the “View on GitHub” button in the header to this page.
Practical Keys to Trout Insects
While it is possible to cast flies to trout and catch fish without having any knowledge of the insects the flies are imitating, most fly-fishers find they do better when they know a little something, say at the level of distinguishing caddisflies from mayflies or stoneflies. These keys are meant for those who want to go much further, not only to distinguish the insects in greater detail, but also to understand their particular lives and livelyhoods.
There are two documents in the zip, one a key to the immature forms (nymphs and larvae) and the other a key to the winged forms (pherates, duns and adults). The first document contains a considerable amount of introductory material that has some relevance to the second as well. Both keys include specific information on habitat and behavior that is useful to the fisher.
The usual scientific keys to insect identification, which go through the genus to the species level, are not particularly practical on the river since most of the key descriptors are only apparent under microscopic examination, and sometimes even require dissection. The present keys are much more limited, in that they only identify the relatively small number of Western U.S. insects whose abundance and occasional concentration make them attractive to selectively feeding trout, but they are practical in that the key descriptors are all visible to the good naked eye, and clear under the small magnification provided by the close-up glasses often used by older fly-fishers when tying on their flies. Under a 10x hand loupe, all the descriptors are prominent.