Caddisfly larvae are tiny rock masons. One built this case

Caddisflies dwell in creeks and are a favorite food of trout. Their larvae live underwater and build these intricate structures – made of tiny stones – to protect themselves from predators and from the rush of the stream. Sheryl Garrison – who captured the photo above on September 23, 2023 – told EarthSky:

The case of a caddisfly – constructed with silk and rocks from the creek bed – serves as a portable protective shelter until the larva pupates. Recent studies have shown evidence of microplastics in some casings. But this one emerged from a mountain creek in the Rockies. Its case was constructed with argillite, limestone, dolomite, and igneous rocks.

And she wrote at her blog:

This crystal-clear creek brings me hope … [Caddisfly larvae] are an indicator of a healthy, functioning ecosystem. The structure in the image is a casing built by the caddisfly out of silk and stones from the creek bed. It serves as a protective stone house for the aquatic insect until it crawls to the water’s edge and pupates.

By the way, the “glue” that holds together the intricate rock structures of caddisfly larvae is particularly remarkable stuff. The larvae secrete this glue – which scientists call “silk” – from a gland under their chins. It works a bit like double-sided tape. But caddisfly silk can stick rocks together, even under water!

If scientists could learn to mimic it, they could use it for human medicine …

Thank you, Sheryl! Find out more about caddisfly cases and the possible future uses for caddisfly silk in the video below:

Bottom line: A longtime contributor to EarthSky Community Photos, Sheryl R. Garrison, captured this cool image of a rock casing built by a caddisfly. Read Sheryl’s story here.