The Urban Pantheist

Urban species #069 : Log cabin caddisfly (Family Limnephilidae)

Spend some time looking into the freshly thawed water of a pond or stream in late winter, and you will notice tiny bundles of sticks moving about. These are the protective cases of caddisfly larvae, that the larvae make themselves. They bite fallen leaves, plant stems, and other debris into pieces and glue it all together with their silk. The case camouflages the larva, and provides physical protection from predators. The head and legs of the larva protrude from the case while moving about and feeding, rather like a hermit crab, but when alarmed the whole insect is retracts and is hidden. Each family of caddisfly makes a distinctive case type which gives it a common name such as cigar tube caddisfly, or as above, the log cabin caddisfly. Log cabin caddisfly larvae feed on detritus; other kinds feed on salamander eggs.

When the larva is ready to become an adult, it seals up its case and becomes a pupa. After metamorphosis, the adult caddisfly (which looks somewhat like a moth, with long antennae) chews it's way out, floats to the surface, and flies away.

Caddisfly larvae are important to the wetland ecosystems that they inhabit. They mechanically break down leaves and other vegetation, helping it decompose, and they are an important source of food for salamanders, turtles, and fish. The EPA considers caddisflies to be moderately pollution tolerant, which may explain why we encounter them in the Muddy River in relatively clean Olmsted Park, but not further downstream in the dirtier Riverway Park.
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