To attract and catch a fly simply leave the piece of trash outside somewhere on your island and walk away. At some point the critter will appear buzzing around the rubbish ready for you to catch it with your bug net.08-Nov-2021,
How do you catch flies in Animal Crossing?
Note that there is a chance for this to occur — it's not guaranteed to happen immediately. One strategy to find the Fly is to simply leave the trash outside a location you often pass by and just wait until eventually the fly appears. This could take a couple hours or days until you finally spot one though.