Caddisflies resemble small moths. In fact, scientists think that caddisflies are distant relatives of moths and butterflies. Moths have scaly wings, so scientists call them Lepidoptera. Caddisflies have hairy wings, so scientists call them Trichoptera. The names of both insect orders come from Greek words that describe their wings.
Some people use the name “sedge fly” or “rail fly” when they are talking about caddisflies. No matter what name they are called, caddisflies are not related to houseflies. Caddisflies have four wings while houseflies only have two wings.
Depending on the species, adult caddisflies can be as small as 1/16″, but some are as large as 2″ in length. They have two pair of hairy wings. The front wings are often longer than the back wings. When they are resting, they hold their wings like a tent above their body.
There have been reports of people suffering allergic reactions when there were large numbers of caddisflies around. Scientists suspect that the hairs from the wings of the caddisflies caused these reactions.
Caddisflies have long, slender antennae. The antennae are often longer than the body of the insect. The caddisflies do not have long mouthparts like butterflies have. Many caddisflies are brownish-colored, but some can be brightly colored.
Caddisflies are common in most parts of the United States. They are usually found near bodies of water – ponds, streams, and even temporary pools. The adult caddisflies only live for a few weeks. They deposit their eggs into the water. The eggs hatch in the water and the larvae are aquatic. They stay in the water while they develop into adult caddisflies.
Caddisfly larvae have slender bodies. They might be mistaken for caterpillars. They have gills on their abdomen. These gills enable the larvae to breathe underwater. Caddisflies do not breathe air until they come out of the water as adults.
Scientists often classify caddisflies by the way the larvae behave in the water. Larvae of some species make protective cases. Some larvae spin silk to make their case. They often cover the silken case with gravel or sand. One species makes a case that looks like a snail shell. Other caddisfly larvae use hollow sticks as shelter cases. They carry the stick around as they search for food
A few larvae are called “free living” because they do not use a shelter case. They move about in the water to find food. Many of the “free-living” larvae are predators. Some caddisfly larvae make nets that they use to catch tadpoles, minnows, and other small prey.
Some caddisfly larvae feed on algae. They scrape the algae from underwater rocks. These algae-eating larvae help keep the water clean. Some species feed on debris that they find on the bottom of the pond or stream. Scientists often measure the quality of the water by the number of caddisflies that are present.
Caddisfly larvae are important food for many types of fish. Most caddisfly species require several months to develop, so there is usually only one generation per year. There have been reports of caddisflies becoming hazards to drivers when they swarmed in large numbers. Caddisflies are often attracted to light and they sometimes gather near buildings or streetlights.
Even though they are attracted to lights, adult caddisflies are not usually pests. If a large number of them gather around the porch light, try turning the porch light off for a few nights. If that doesn't work, it may be necessary to use an insecticide that is labeled for flying insects.