Attribution: James Lindsey at Ecology of Commanster [CC-BY-SA-2.5 or CC-BY-SA-3.0]
Varies from 1/16 inch to 1 inch in length, depending on the species.
Brown to black
Caddisflies are slender, elongated insects with hairy, almost moth-like wings that they hold tent-like over the abdomen. They have long, thread-like antennae, usually as long as the body. Caddisflies are important insects in freshwater ecosystems where they breed in streams, ponds and lakes, serving as food for a wide variety of aquatic animals, especially fish. The adults of a particular species emerge from the water at about the same time, sometimes forming clouds of insects over the water. These adults are strongly attracted to lights on buildings located near waterways, thereby becoming “pests” at times. More commonly, one or two caddisfly adults accidentally fly into a home where the homeowner then mistakes them for moths and may become concerned.
Caddisfly larvae are common inhabitants along the bottoms of rivers, streams, ponds and lakes. The larvae of many species build protective cases over their bodies using available bits of sand, twigs and other debris. These cases are sometimes quite intricate and serve to camouflage the larvae from potential predators. Caddisflies are an important insect to the fly fisherman who will use many variations of artificial flies to mimic caddisfly larvae and adults to effectively lure and catch trout.
Caddisflies cannot be controlled through treatments because they breed in aquatic environments and only become pests when attracted by outdoor lights to buildings. Any emergence of caddisflies, however, should last only a few days. Where these insects are being a problem, exterior light fixtures should be turned off or have yellow “bug lights” bulbs installed. Commercial buildings should use sodium vapor lamps in fixtures rather than mercury vapor lights.