When we were finishing retrieving an aquatic bottle trap from Blue Hill today we happened to find some tubes of carefully interwoven pine needles. While these types of things would normally go unnoticed by being inconspicuously small and blending in with the neighboring debris that has been swept to shore, what we were actually looking at was the discarded casing of a caddisfly larva (from the order Trichoptera).
Caddisfly larva typically spin webs from glands in their mouth and, in case building species, will collect surrounding debris and other bits of nature to make their home. They keep both ends of their case open so that they can have a continuous flow of water (going from posterior end to anterior end) in order to breathe. To make sure that they don’t fall out they will hold their home in place by a pair of hooked prolegs at the end of their abdomen. Once they have matured they will bite through the case and abandon their homes to join the world of flight. Caddisflies are adults for merely a week or two of their year-long lives, and often they do not feed when they’re mature. The ability of caddisflies to make their homes from surrounding debris has been harnessed by bug-savvy jewelers to create one-of-a-kind pieces that you can wear.
Other caddisfly larva will create silken nets to filter and funnel water-borne food to their mouth, and some do not make silk cocoon-like structures at all and are free-living in the water. Learn more about other water-linked species in Forest’s blog on the fascinating lives of dragonflies!
Greetings from Terra Nova National Park!
P.S. The Barcode of Life Initiative has a Trichoptera campaign! Check it out at www.trichopterabol.org