The other day, I saw what I thought was a moth flutter past and land on a tree. What I found sitting on the bark, though, was a caddisfly, which is neither a moth nor a fly.
Caddisflies are related to moths, though they don’t have scaly wings. Their scientific order, Trichoptera, means “hair-wing,” which sounds a bit awkward, but you can see the hairs, especially on the wing edges. They spend most of their lives underwater as larvae, where they are a favorite fish food. Many of them, though, have some serious crafts skills to help them avoid being eaten.
It’s tough to identify adult caddisflies unless they’re dead and under a microscope, but the larvae are fairly easily pinpointed by their architectural style. “Case-building” caddisflies use a sticky silk they generate from their mouths to cover themselves with things like pebbles or bits of grass. Some of these permanent jackets are beautifully geometric, either with long lines, a log-cabin style, or a bejeweled look. I saw the pine needle-clad caddisfly larvae pictured here on a lake near the coast; the rest of the images are from Mount Pisgah.
“Net-spinning” caddisflies make traps from their silk to catch food in flowing water. Larval caddisflies may be carnivores, omnivores or vegetarians, but the adults either don’t eat at all or only sip nectar.
Most sources say there are about 1,400 species in North America. One of my favorite recent finds at Mount Pisgah is this black caddisfly in the Mystacides genus. It has an elegant pendant shape and ridiculously long, striped antennae. What about those black, furry, bottle-brush-like things? Are they another set of antennae? No, they’re mouthparts, and they’re often held out to the side, but can fold up like this at rest. Wait! Didn’t I just say adults don’t eat? Yes indeed. It’s another insect mystery ready for investigation.
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Excerpt from Paul Weamer’s “The Bug Book” in Hatch Magazine: https://www.hatchmag.com/articles/under-appreciated-caddisfly/7712759. Accessed 11/5/21.
North Country Public Radio on caddisfly silk: https://www.northcountrypublicradio.org/news/story/43265/20210520/natural-selections-the-many-virtues-of-the-silk-making-insect. Accessed 11/5/21.