Caddisflies

While examining the critters of the vernal pools, we also found Caddisfly larave.  The larvae of many species of Caddisfly build cases around them and the case is both species-specific and habitat specific.  The one pictured below seems to have used dead plant material and arranged it lengthwise.  Can you distinguish its head and thorax sticking out at the lower left end of the picture?

Caddisfly Larva

The first Caddisfly larvae I learned about were in a stream and had built their cases from small pebbles.  Since then, I have found many other species in different watery habitats with cases built from leaves, twigs, and other organic material.  Here’s one from another pond with a different arrangement of plant material:

Caddisfly Larva

Here is a 22 second video of the this fellow moving about.  If you have your sound on, you’ll hear voices speculating about the critter’s emotions and food preferences…


I don’t think he was unhappy.  I think that’s how he steers!  And I don’t think he eats mosquito larvae – though I could be wrong.  Most often in vernal pools I see them munching on amphibian egg masses.

While the larvae and pupae are aquatic, the adult will be airborne:

Caddisflies attach their cases to some underwater object, seal the front and back apertures against predation though still allowing water flow, and pupate within them. Once fully developed, most pupal caddisflies cut through their cases with a special pair of mandibles, swim up to the water surface, cast off skin and the now-obsolete gills and mandibles, and emerge as fully formed adults. <source>

Adults hatch synchronously making it easier to find a mate.  (Fly fisherman time some of their outings to coincide with these hatches.)  The adults in most species don’t eat.  Here’s a particularly large species photographed by Jenn Forman Orth:

I’m pretty sure this is not the species that uses vernal pools… but the adults of most species have this same basic body shape.

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