CADDISFLY

member of one of some 7,000 species of mothlike aquatic insects of the order Trichoptera. Caddisflies, generally dull brownish in colour, are found in freshwater environments, often on plants near the water's edge. They may be distinguished by the characteristically hairy wings folded rooflike over the abdomen and by the long antennae. Caddisflies are found in freshwater habitats all over the world, and a few species frequent brackish water and tidal regions. Many fossils have been preserved from the Early Jurassic Period (about 185,000,000 years ago). The bodies of caddisflies are divided into head, thorax, and abdomen. The head contains the mouth, antennae, and eyes. The mouth typically has poorly developed mandibles and a hypopharynx adapted to sucking liquids. The antennae are long to very longthey are often longer than the wingspanand are many-segmented. The eyes are relatively small. The thorax bears a pair of walking legs and two pairs of wings. Flight is weak and unsteady, however. Most caddisflies take to the air at night and, like moths, are strongly attracted to light. The species that fly by day frequently do so in swarms. Most feed on plant juices and the nectar of flowers; a few, however, are predacious. The female scatters her eggs into water or places them on rocks or plants at or beneath the surface. The eggs hatch in a few days to release the larvae, or caddisworms, which in nearly all species live in fresh water. Depending on the species, they may prey on algae, plants, or other insects. Some larvae are free-living, but many construct a portable case made of grains of sand, bits of shells, and plant debris. A silky substance secreted by labial glands acts as a glue to hold the case together. The cases are usually tubular, open at both ends. The case covers the abdomen, while the armoured head and the thorax protrude from the front. In the advanced stages of their development, many larvae attach the cases to a solid object, close both ends, and pupate inside; others construct a separate cocoon. When the pupa matures it cuts or bites its way out of the case or cocoon and swims to the surface of the water to complete the transformation into the adult stage. Caddisflies are an important part of the freshwater ecosystem. They help clean the water by consuming plant and animal debris. They also serve, both in larval and adult forms, as an important food for fish in freshwater streams and ponds; trout, in particular, prey on caddisflies, which is why the flies used by anglers are often modelled on them. any of the mothlike aquatic insects that constitute the order Trichoptera. The adult, attracted to light at night, often lives near lakes or rivers. Because fish feed on immature, aquatic stages and trout take flying adults, caddisflies are used as models for fishermen's flies. Additional reading F.C.J. Fischer, Trichopterorum Catalogus, 16 vol. in 10 (196073), a checklist of world Trichoptera; N.E. Hickin, Caddis Larvae: Larvae of the British Trichoptera (1967), an excellent, comprehensive work on caddis; M.E. Mosely and D.E. Kimmins, The Trichoptera (Caddis-Flies) of Australia and New Zealand (1953), a basic study of fauna that includes species of importance in world classification; H.H. Ross, The Evolution and Past Dispersal of the Trichoptera, A. Rev. Ent., 12:169206 (1967), a brief work including a revolutionary reclassification of the group; and Gary LaFontaine, Caddisflies (1981), for the general reader. Keith Arthur John Wise