This is the 1st in what may be a long series on Caddis flies. As with the Mayfly Entomology series I did, I will be concentrating specifically on the species within the Hatch Chart that the Lanesboro Fishery put out, you can view it here. Armed with research tools and the chart I will be grouping the species into appropriate groups and posting information on each. A few things should be discussed though before delving into the specific species of Caddisfly here in Southeast, MN.
I feel that Gary LaFontaine places special emphasis on the pupal state of a caddisfly and because the caddisfly has this stage in it’s development I thought this would be a good place to give some general information on the life cycle of the caddisfly.
Egg’s: Are deposited by female caddisflies some of whom deposit them by diving under the water fully submerging themselves and depositing the egg’s in a good location. Some species of caddis also fully submerge themselves but do it by crawling into the water from any location protruding from the surface. This is a good thing to note if you see concentrations of flies surrounding branches sticking out of the water or rocks.
Larva: Caddisflies exist as a Larva for most of the life cycle and as such these Larva are of great importance to the fly fisherman. As you probably know they come in many shapes and sizes. Anyone who has turned up a rock here has seen them even though they may not have known what they were looking at. Caddis larva live in a few ways, some species live uncased and cling to rocks with a spur or barb that protrudes from the back end of the larva. These typically are longer, green-olive and sometimes extremely bright green in color. Some species build cases from small pebbles weaved together with silk. Some simply weave a shell of silk around them while others build small bunkers in which they fully cover themselves like a small bomb shelter. The picture of the un-cased larva is of the underside and shows the tail which grasps onto rocks well.
Pupa: When the caddis fly is ready and water conditions are right a larva will begin to change into a pupa. This pupa is different from a rising nymph in that caddis use a thin layer surrounding them which inflates with tiny bubbles to help them rise to the surface. LaFontaine goes into great detail with regards to this process because it was viewed improperly before his diving experiments and observations. The caddis will remain just below the surface after it has inflated its coating for potentially quite some time making this a good condition to imitate. With that LaFontaine used the Dupont product Antron to simulate the bubbles and how trout perceive the light reflected by these bubbles. The pupa remains just below the surface until the fly is about to emerge in which it does so fully able to fly off immediately unlike the Mayflies who must typically hang around the surface drying its wings.
Adult: The adult leaves the water immediately. Caddis flies can be seen in there adult form dancing over riffles and preparing to mate and deposit eggs thus starting the cycle over again.
Once again I will note that I am not an expert but attempting to learn as much as possible specific to the area of Southeastern, MN which may or may not pertain to Southwestern Wisconsin and Notheastern Iowa. I encourage comments which will either point out a flaw in my writing or will provide me with more information.