Fly Fishing Entomology

Flyfishingentomology.com is a website made by a local entomology enthusist. while it is made specifically for washington, much of the information can be used for most of the pacific northwest and alot of the western Us. The site includes a hatch chart, indentifications, a list of insects, and much more. You'll just have to go check out the site.

Note: This article was taken from Jim Schollmeyer's book called Hatch Guide for Western Streams

Ephemeroptera (Mayflies)

With their upright wings, mayflies are the easiest insects to see floating on the water and it is possible that fly fishing itself was born when early anglers first observed trout feeding on these high visible flies.

Mayflies undergo incomplete metamorphosis, which means that the life cycle, typically lasting a year, consist of only three stages; egg, nymph, and adult. The major part of a mayfly’s life is spent in the nymphal stage.

Based on behavior and body shape, mayfly nymphs are divided into four groups: burrowers, clingers, crawlers, and swimmers. Burrowers have a long, oval-shaped body with fringed gills and visible tusk-like mandibles. Clingers have a flattened body and a head equal to, or less than, the width of the abdomen, which has oval or unfringed, forked gills along the top margin; except for a few species, crawlers have no tusk like mandibles. Swimmers have a round streamlined body with a head equal to or less than, the width of the abdomen. The abdomen has oval gills positioned along the sides, and the edges of the tails are fringed with fine hair.

Nymphs go through 20-30 molts as they grow, and between the last few molts the wing pads darken as the wings develop. At emergence most mayfly nymphs swim or drift to the surface and emerge as adult floes. In a few mayfly families the nymphs emerge under water and the adults swim to the surface, or the nymphs crawl out of the water and hatch on shore.

Adults go through two phases. The first is commonly called a dun, and the second a spinner. Duns are newly hatched adults that emerge from the water and fly to streamside foliage. Their wings have opaque coloring, and in this phase the adults are unable to mate. After as little as an hour or as much as three days, the dun sheds it out covering and the spinner emerges. Spinners have clear wings. After mating, the female begins depositing their eggs; usually on the water’s surface, though a few species crawl under water and attach their eggs to the bottom. After depositing their eggs, the females fall spent on the water creating a “spinner fall.”

Trichoptera (Caddis)

When at rest, adult caddisflies fold their, fine hair-covered wings low over their abdomens, creating a tent-shaped profile that is a characteristic feature of the insects. Caddis undergo complete metamorphosis, passing through four stages in the life cycle: egg, larva, pupa, and adult. Most of the insect’s life is spent in the larva stage. At maturity, the larva builds a cocoon, and pupation occurs within two to eight weeks. At the end of pupation, these caddisflies; called “pharate adults”, enclosed inside transparent shucks, look like adult insects with their wings folded around their bodies. They chew out of their cocoons and swim to the surface where their papal shucks split open and the adults emerge. Adult males form mating swarms to attract the females, and mating takes place while at rest in streamside foliage. Late, females lay their eggs either by depositing them on the surface or by crawling or swimming under water and depositing them on submerged objects. Adults live from one to four weeks. Most caddisflies living streams have a one-year life cycle. Though a few have two generations a year.

Caddisflies are divided into five groups, based on the larva’s behavior: (1) free-living, (2) saddle-case caddis, (3) net-spinning caddis, (4) tub-case caddis, (5) purse-case caddis. Free live caddis larvae do not have a case or shelter to hide in; they are predators that roam the streambed. Saddle-case caddis larvae build dome-shaped cases that completely cover them except for a small opening at each end. Net-spinning caddis larvae build shelters and spin a web next to the entrance to catch their food. Tube-case caddis larvae build portable cases that enable them to move around and provide a retreat when disturbed.

Plecoptera (Stoneflies)

Stoneflies, from the order Plecoptera, require flowing water to live, and the highest population densities are found in cool, well-oxygenated streams. During their life cycle, they undergo incomplete metamorphosis, passing through only three stages of development: egg, nymph, and adult. Most of their lives are spent in the nymphal stage, which varies in length from seven months to four years. Mature nymphs crawl from the water and the adults emerge on land. Mature nymphs crawl from the water and the adults emerge on land. Mating also takes place on land. Egg-laying habits vary, but species that fly out over the water and touch down briefly to release their eggs are the most important to anglers.