Hatches - a.k.a. Trout Food.
Mayflies (Ephemeroptera)
Mayflies begin life as an egg, and hatch into an aquatic stage known as a nymph. Nymphs usually live about a year but may last two years or more, or just a few months, depending on the species. Some mayfly species have two broods per year, making them important in the spring and again in the fall when the next generation matures.
Mayfly nymphs range in size from 4mm to 40mm and most often have three tails (sometimes two). Some mayfly nymphs are burrowers, others have adapted to cling to rocks in fast water, so each nymph species has a different body shape and design. Most are dark on top (mottled brown, tan, or dark olive) with a lighter-colored underside.
When a mayfly nymph rises toward the surface and splits its shuck, the insect that emerges is called a dun (technically a subimago or pre-adult). They have two large, upright wings, two or three tails, and most have two very small hind wings. The wings are opaque and their bodies are often drab-colored.
Duns are the mayflies that ride the waters surface in an upright position while their wings dry before taking flight. It is a cliche, but fly fishers often say they look like miniature sailboats. When duns are on the water, you are in the hatch situation fly fishers live for, and it’s time to fish with dry flies, which float on the surface of the water.
After they hatch, mayfly duns fly to streamside vegetation where they molt or shed their skins and enter the adult or imago phase fly fishers call spinners. The change from dun to spinner often results in a different body color, and spinner tails are longer than dun tails. The most noticeable difference is that the wings of mayfly duns are opaque or cloudy. Spinner wings are usually clear.
A short time after molting into spinners usually within 24 hours the mayflies fly back to the water and gather in large swarms over riffle areas, where they mate. This most often happens late in the evening or early in the morning.
The females lay eggs and then die in the egg-laying process. Males continue to fertilize eggs until they also fall spent to the water, with their outstretched wings flush with the water’s surface. Trout sometimes prefer spinners over duns because they have learned that spinners have no chance to escape they are dead and are easier meals. Also, duns hatch over a relatively long period of time, while spinners fall to the water en masse, creating an irresistible feeding opportunity.
Caddisfly (Trichoptera)
Many species of caddisfly larvae enter a stage of inactivity called the pupa stage for weeks or months after they mature but prior to emergence. Their emergence is then triggered by cooling water temperatures in the fall, effectively synchronizing the adult activity to make mate-finding easier. In the Northwestern US, caddisfly larvae within their gravel cases are called 'periwinkles’.
Caddisfly pupation occurs much like pupation of Lepidoptera. That is, caddisflies pupate in a cocoon spun from silk. Caddisflies that build the portable cases attach their case to some underwater object, seal the front and back apertures against predation though still allowing water flow, and pupate within it. Once fully developed, most pupal caddisflies cut through their cases with a special pair of mandibles, swim up to the water surface, cast off skin and the now-obsolete gills and mandibles, and emerge as fully formed adults. In a minority of species, the pupae swim to shore -- either below the water or across the surface -- and crawl out to emerge. Many of them are able to fly immediately after breaking from their pupal skin.
The adult stage of caddisflies, in most cases, is very short-lived, usually only 1 1/2-2 weeks, but can sometimes last for 2 months. Most adults are non-feeding and are equipped mainly to mate. Once mated, the female caddisfly will often lay eggs (enclosed in a gelatinous mass) by attaching them above or below the water surface. Eggs hatch in as little as three weeks.
Caddisflies in most temperate areas complete their life cycles in a single year. The general temperate-zone lifecycle pattern is one of larval feeding and growth in autumn, winter, and spring, with adult emergence between late spring and early fall, although the adult activity of a few species peaks in the winter. Larvae are active in very cold water and can frequently be observed feeding under ice. In common with many aquatic insect species, many caddisfly adults emerge synchronously en masse. Such emergence patterns ensure that most caddisflies will encounter a member of the opposite gender in a timely fashion. Mass emergences of this nature are called 'hatches' by salmon and trout anglers, and salmonid fish species will frequently 'switch' to whatever species is emerging on a particular day. Anglers take advantage of this behavior by matching their artificial flies to the appropriate fly.
Stonefly (Plecoptera)
Stoneflies have a generalized anatomy, with few specialized features compared to other insects. They have simple mouthparts with chewing mandibles, long, multiple-segmented antennae, large compound eyes, and two or three ocelli. The legs are robust, with each ending in two claws. The abdomen is relatively soft, and may include remnants of the nymphal gills even in the adult. Both nymphs and adults have long, paired cerci projecting from the tip of their abdomens.
The name "Plecoptera" literally means "braided-wings", from the Ancient Greek plekein ("to braid") and pteryx ("wing"). This refers to the complex venation of their two pairs of wings, which are membranous and fold flat over their backs. Stoneflies are generally not strong fliers, and some species are entirely wingless.
The nymphs (technically, "naiads") are aquatic and live in the benthic zone of well-oxygenated lakes and streams. A few species found in New Zealand and nearby islands have terrestrial nymphs, but even these inhabit only very moist environments. The nymphs physically resemble wingless adults, but often have external gills, which may be present on almost any part of the body. Nymphs can acquire oxygen via diffusing through the exoskeleton, or through gills located on behind the head, on the thorax.[10] Due to their nymph's requirement for well oxygenated water, the species is very sensitive to water pollution. This makes them important indicators for water quality. Most species are herbivorous as nymphs, feeding on submerged leaves and benthic algae, but many are hunters of other aquatic arthropods.
The female can lay up to one thousand eggs. It will fly over the water and drop the eggs in the water. It also may hang on a rock or branch. The eggs typically take two to three weeks to hatch, but some species undergo diapause, with the eggs remaining dormant throughout a dry season, and hatching only when conditions are suitable. The insects remain in the nymphal form for one to four years, depending on species, and undergo from 12 to 36 molts before emerging and becoming terrestrial as adults. Before becoming adults, nymphs will leave the water, attach to a fixed surface and molt one last time. The adults generally only survive for a few weeks, and emerge only during specific times of the year when resources are optimal. Some do not feed at all, but those that do are herbivorous. Adults are not strong fliers and generally stay near the stream or lake they hatched from.
Midges (Dipera) (family-Chironomidae)
Being true flies, midges (in the family Chironomidae) have only one pair of wings. They look a lot like mosquitoes: small and dainty, rather soft-bodied, with long, narrow wings and long, skinny legs; males often have feathery antennae, used for sensing the high-pitched sounds of female wings. Unlike mosquitoes, midges, at rest, tend to hold their first pair of legs forward and upward (while many mosquitoes, at rest, hold their hind legs outward and upward). A midge's up- and outstretched forelegs can resemble antennae, at a glance. The tarsi ("foot" portion) of the forelegs, in many midges, is very long. Midges lack scales on their wings (while mosquitoes' wings do have scales). Fine details of anatomy, including wing venation, are important for identifying midges beyond the most basic groups (tribe, subfamily, or genus). The larvae of many midges are called bloodworms, for they are red from the hemoglobin molecules within their narrow bodies. They live at the bottom of lakes, ponds, and other aquatic habitats and often construct tubes from fine sediment and mucus. Size: Length: Most are less than 3/8 inch long..