Adults: Adult caddisflies are slender moth-like insects. They have two pairs of membranous, hairy wings that are folded tent-like over the body when at rest. They have long fuzzy antennae that extend back over the body, and are often black to tan in color. Adults breath via thoracic spiracles.

Larvae: The abdomen is grub-like, soft-skinned with or with out filamentous gills. Often there is a pair of anal prolegs with hooks on them. The thorax may be either hard (scleritized) or soft but always has three pair of legs. The head resembles a capsule with compact mandibles. Caseless species have branched gills along the abdomen while those with cases have single gill filaments along the abdomen.

Habitat: Adults can be seen flying low over the water or on vegetation in the vicinity of their hatch site. They are attracted to lights at night. While all caddisfly larvae are aquatic, habitat preference within aquatic systems is generally related to characteristics of the larval case. See the “ecology” section for more information.

Ecology: Caddisflies spend most of their lives as larvae. During the larval stage most caddisflies live in tubelike cases of twigs, sand, leaves, or other material. These are so distinctive that the type of case made can identify species. Most larvae feed on plant material but a few are predaceous.Larvae are organized into five groups according to their case construction habits. Free-living forms do not build a case (but do build a cocoon), and are generally predators in cool, running water. Saddle-case makers build portable cases of rock-fragments like the shell of a tortoise. They live in running waters or wave-swept lake shores, and graze on diatoms and organic matter found on rock surfaces. Purse-case makers construct portable purse-shaped cases. They inhabit all types of permanent waters where they feed on algae. Net-spinners or retreat-makers build anchored retreats in moving water. They use capture nets to filter food particles from the current. Tube-case makers construct portable, tubular cases of various shapes, sizes, and materials. Cases aid in respiratory efficiency allowing survival in more stagnant waters. Swarms of caddisfly adults are most common at dawn and at dusk near their hatch sites. Some species feed on plant nectar as adults, while some do not feed at all. In many aquatic systems caddisflies exhibit high species richness and sometimes form the dominant food source for fish and birds.

Reproduction: Caddisflies undergo complete metamorphosis (“holometabolous”: egg—larva—pupa—adult) similar to their close relatives, the lepidopterans (butterflies and moths). Like the larval stage, the pupal stage takes place underwater. Adults may live from two weeks to two months. Mating occurs either in flight, on vegetation, or on the ground. Eggs are laid in masses or strings over the water or attached to rocks or other objects in -- and sometimes near -- water. In some species the female dives and deposits her eggs on the bottom.