Caddisfly Are Cool

There’s been a lot of fuss about caddisflies lately, thanks to the item on BuzzFeed ( with pictures of caddisfly-assembled jewelry.

I was poking around my old saved blogdrafts, and found this from some years back that seemed appropriate. It’s a scan I made of some of my caddisfly case collection.

Caddisflies are insects in the Order Trichoptera, which means “hair winged” — and indeed they have tiny little hairs on their wings. They are rather related to the Lepidoptera — butterflies and moths. Adult caddisflies basically look like little tiny moths with long skinny antennae, while caddisfly larvae look like little caterpillars, and they also spin cocoons to pupate.

Except that caddisfly larvae live underwater, in streams and lakes. Not all build cases — some go around naked, some form little silk tunnels, while others build little nets with rocky goalposts to trap debris and food from the flowing current, like these Hydropsyche larvae I had in my aquarium once.

You can see this one using its silk glands to connect strands from one rock to another, and back and forth. (No word on what kind of web the crack-dealing caddis spins.)

And as you can see, they can get quite territorial. HYDROPSYCHE BATTLE ROYALE!

But the ones that do build cases make extraordinary ones. Caddis larvae wear them like hermit crab shells — although in addition to providing shelter, for some species, the cases also form a chamber through which oxygenated water can be forced through by wiggling their little bodies.

Take a look at the cases in the image above — they’re made of all different kinds of materials.

  • Gumaga makes them with tiny sand grains.
  • Amiocentrus makes them with strands of hairy algae, circling them around in rings into perfect little cones.
  • Some Lepidostoma and Brachycentrus make little log cabins using sticks and leaf debris. They even have little square corners to them.
  • Heteroplectron skips the whole building process and just finds twigs and sticks it can stick its old self in. These larvae can get quite big, and it’s impressive when you find a sizeable twig (OK, “big” and “sizeable” here is like over 1 inch) with an equally sizeable grub in it.

For more on caddisfly larvae, consult the classic Glenn Wiggins text Larve of the North American Caddisfly Genera (Trichoptera):

— Ben


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