Caddis flies

(Trichoptera)

Background
Development
Characteristics
Importance
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Background:
Worldwide, there may be 7,000 different species of caddis flies. They get their name Trichoptera because of their body characteristics. Tricho-, means hair, and -pter means wings. This is because the adult has wings that are heavily covered with hairs. In the larval stage, they build cases made from small gravel, sand grains, or plant material. They can be found in streams and ponds where the adults come out mostly at night.
Development:
The caddis flies go through five larval stages, a pupal stage and a winged adult stage. This is usually completed once a year with the metamorphosis taking about three weeks. The females will lay their eggs either near the water or in the water. They can actually dive into the water and cement their eggs on stones and other substrates. The hairs around the body act as a gill, allowing carbon dioxide and oxygen to diffuse in and out. This allows the caddis fly to hold her breathe for longer amounts of time. Eggs are usually laid in masses of about 700, but this varies by species. Once the eggs have hatched they begin their first larval phase. Three more phases will follow until the larvae enter their fifth and final stage. During this time, the larva prepares itself by feeding. When it is ready, pupation will occur. Pupation occurs underwater and can be influenced by temperature, altitude, nutrient reserves, and more. When the pupa is ready to emerge as an adult, it cuts out of the pupal chamber and swims to the surface. Once it has emerged from the water, the caddis fly can live anywhere from a few weeks, to a few months.
CASES
Some larvae are free living, while others produce mobile cases. These cases serve as defense mechanisms during the development period. These cases also transmit touch sensation information to the larvae inside. They can also attach to substrates to prevent the larvae from being swept away.
Cases are usually made up of plant material, gravel, sand, or a mixture of all three. Cases can be used to identify species, for they usually build them with the same things and the same size depending on their resources. Most summer species use mineral resources from fallen leaves to produce their cases. Some species are even capable of producing silk to make their cases.
Characteristics:
•Body and wings are covered with setae (silky hairs)
•Most species live in a protective case that they build from organic materials
•Gills

Immature:
•Caterpillar-like body enclosed in case
•6 hooked legs at tip of abdomen
•Mouth capable of chewing

Adult:
•Antennae
•Reduced mouth
•2 pairs of wings
•Gray, tan, or black in color

Importance:
Caddis flies are a primary source of food for birds and fish. Larvae are an indicator of water quality because they are very sensitive to pollutants. Fisherman often uses adult forms as bait. They are also important because their nets and cases provide useful impedance to water in ditches and canals.
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