Caddis flies; the first mobile home.

Caddis fly larva in its test.

The saying, "Home is where your heart is," is certainly true for Caddis Fly larvae because their heart is tucked very nicely in the midst of their self-built home.  The home is not any roughly hewn assemblage of whatever happens to be about.  Each species of caddis fly is very particular about the building materials that go into constructing their mobile edifice.  One species is fond of small twig-like components that produce a rectangular test, another uses sand.  The above one prefers the use of small pebbles.

Unlike hermit crabs that require a snail shell from its dead benefactor, caddis fly larvae build their own from scratch.  They also don't trade up as they grow like their crustacean cousins, rather the test starts off small like its owner and is built up over time.  It's a mobile home with additions.  The insect uses silk to join the various bits of hubris when the need arises; the pieces becoming larger at each instar.  The instar is the phase between one molt and another, usually there are 5 of them, each one built with room to grow. 

Caddis fly larvae breath underwater by a series of gills coming off their abdomen.  Gas exchange is facilitated through a variety of methods, depending on the species.  Those living in moving water have the advantage of liquid being forces past the breathing appendages.  Stagnant water required undulations of body or the gentle movement of gills to encourage water flow.  Diffusion plays its part in all circumstances.

Fishermen have little direct use for the larvae, but the adults represent the pinnacle of bait.  Many a fly tier has recreated the winged insect to lure awaiting dinner to its doom.  The mature flies are a tasty morsel for aquatic predators.  After breeding the caddis fly adults must touch the water with their abdomens to lay an egg, their proximity perfect for fish.  Some may inadvertently fall into the water and become stranded there; others die and fall in.  Too bad the adults couldn't bring their homes with them from their larval stage - it might make them much less palatable.

Thanks for reading.   www.ericspix.net   Eric Svendsen