Caddisfly larvae construct silk cases decorated with pieces of gravel, sand, twigs, snail shells, and other natural debris. This most often happens during winter months, so the theory behind this behaviour is that they do it to protect themselves from the cold, harsh weather.
Duprat “introduced beads, pearls, turquoise, and 18-karat gold pieces into their environment and let them construct tiny gilded sculptures. Duprat has been collaborating with the larvae since the 1980s. Learn more about his work at Cabinet Magazine.”