Caddisflies: Trichoptera

Adult caddisflies are slender, mothlike insects that are usually drab in color, although some species are very brightly marked. They measure 0.048 to 1.76 inches (1.2 to 40 millimeters) in length. Both compound and simple eyes are present. Compound eyes have multiple lenses; simple eyes have only one. The chewing mouthparts are made up of long, fingerlike appendages on either side of very small jaws. The antennae (an-TEH-nee), or sense organs, are long, threadlike, and held together out in front of the body. Both the head and the thorax, or midsection, have wartlike bumps. All four wings are similar to one another in size and appearance. They are folded like a roof over the body when at rest. Most of the wing veins are straight and have very few branches, or cross-veins. The females of some species have very small wings and cannot fly. The legs are long, slender, and have scattered spines. The ten-segmented abdomen is tipped, with reproductive organs that vary in shape.

The larvae (LAR-vee), or young, resemble caterpillars. Their heads are distinct and hard with strong jaws. Each of the three segments of the thorax has a pair of well-developed legs. A thick plate covers one or more of the thoracic segments. The long, soft ten-segmented abdomen is slender or plump and sometimes has gills along the sides. The last abdominal segment has a pair of leglike structures.