These are one of the largest family of flys.  The Larvae tend to be oblong, cylindrical and somewhat tapered toward the head.  The head is retractable and only partially hardened.  The last abdominal segment usually has several finger-like lobes.

Order:  Trichoptera

These invertebrates make up a large part of benthic communities.  Some species are free-living while others make case retreats out of silk, sand grains, pebbles, or bits of plant material. 

All caddisflies have hard-shelled head capsules.  Sometimes the first three segments behind the head also have hard-shelled plates on the top surface above the attachments for three pair of legs.  The rest of the body is soft and often cylindrical.  The larvae possess two small hooks on the last segment.

Caddisflies undergo complete metamorphosis and the larvae transform into winged adults in the water.  As adults, caddisflies only live a few days and do not eat at all.

Stoneflies are indicators of good water quality because the nymphs require highly oxygenated water.  They tend to inhabit clear cold streams, and are highly intolerant of changes in water quality. 

Stoneflies undergo incomplete metamorphosis.  The aquatic nymphs transform directly into winged adults.  The heads and top surface of the first three body segments on nymphs are hardened.  Their antennae are moderately long to long, and all species have exactly two tail filaments.

Small Stonefly nymphs can easily be mistaken for mayfly nymphs; however, mayfly nymphs usually have three tail filaments and stonefly nymphs have gills around the base of their legs or no gills at all.

Mayflies are usually easy to identify.  The nymphs can be small and squat, or long and slender.  They have three pairs of segmented legs and visible antennae.  They are most easily identified by their three tail filaments, and by the seven pairs of abdominal gills found on most species.  The gills may be either flat and spade shaped, or feathery in appearance.

Mayfly nymphs are often flattened or streamlined to reduce the force of fast currents.  They are most abundant in clear streams, though a few kinds may be found in other habitats.

True flies lack jointed legs.  some have complete, exposed head capsules; others have a reduced retracted head.  The bodies are soft and flexible.

Dragonflies and damselflies are predators.  Their nymphs are not common in fast moving streams, but may be abundant in sluggish waters.  They may be elongated and are a somber grey, green, or brown color.  The body may be smooth or rough and is often covered with a growth of algae and organic debris.