Thanks to the success of Przybylski’s experiment, Scavenger Fly was born in late 2016, starting with an upgrade from a plastic bag to watertight fly boxes. Each box comes with six starter flies, a notebook, a pencil, and instructions, which specify that if you take a fly without leaving one, you should pick up five pieces of trash. Przybylski encourages anglers who purchase a box to add a few of their own flies, and then plant it in a location that’s not impossible to figure out but would take local knowledge to find with a few location clues posted on Instagram with the hashtag #scavengerfly. Anyone who finds the box is asked to take a photo of it and post it with the same tag. Tagged photos of fish caught on flies from the box are also welcomed. The goal, Przybylski says, is for the boxes to become genuinely useful sources of local patterns.