Bottle Fly Trap for Mason Jars

thingiverse

Fill a Mason jar one-third full of water and add a piece of raw fish or meat. Attach the cone or tube section to the lid ring, then secure the top cover into place by inserting it through the four small holes. Within days, as the bait decomposes, flies will begin to fill your trap! White plastic seems to work best because flies are drawn to light and will head towards the underside of the top cover rather than the light shining through the holes. The top cover prevents rain from overflowing into the jar. Pictured is my completed cone trap after just a week or two, with nearly a full quart of green bottle flies! That's quite a catch! This design works best for wide-mouth Mason jars. If you'd like to adapt it for small-mouth jars, I've included the JSCAD file. For optimal performance, print this trap in ABS or another heat-resistant plastic if you live in an area with high temperatures or direct sunlight.