Caddisfly (Tricoptera)

Original drawing by Jill Culley. Caddis case made of tiny sand grains.

The metamorphosis of the caddisfly is complete and usually consists of several instars followed by a pupation period. The larvae of some species undergo a period of non-development in damp substrates during the summer and resume development as a response to shortening day length.

Pupation is nearly always aquatic and takes place in a sealed cocoon. These cocoon cases are generally fixed to an object. The pupation stage generally takes approximately three weeks. The larval and adult stages of the caddisfly are very different with winged, breeding adults which emerge at various times of the year, depending on the species.


Caddisflies are common bottom fauna and can be found in most freshwater lakes and streams. They are found in all substrates and are sometimes found in seepage.

Caddisflies and Water Quality:

Caddisflies, like the mayflies and stoneflies, are important indicators of water quality. Their presence are ecological indicators of good aquatic health. We suspect that the low abundance of caddisflies the lower Emigration Creek,  may be due its use as an urban storm drain system. The pulsing and flushing of the stream due to enhanced flow of storm drains increases the velocity of runoff from a highly disturbed watershed. This results in both degraded chemical conditions as well al episodic physical disturbances to the stream bottom habitat for both mayflies and caddisflies.


Most caddisflies build protective cases around their body and are able to increase the amount of dissolved oxygen passing over the body by undulating the abdomen within the case. these cases provide protection from predators and physical disturbances.

The Caddisflies place in the food web:

Most Caddisflies consume plants, including algae. They also feed on Diatoms and animal debris. Caddisflies fall prey to some predacious insect larvae, birds, frogs, water striders and trout.


McCafferty, Patrick W. 1983. Aquatic Entomology. Jones and Barlett Publishers Inc., Sudburg, MA.

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