Gnat Funnel!

thingiverse

So maybe not for gnats, but this is a 3D printed approach attempt to trap those pesky fruit flies that comes with your bushels of supermarket bananas. My wife had been using rolled up paper funnel + ball pickling jar technique for couple years with success. Google for details what to use, but we've been filling bottom 1 to 2" of the jar with water, vinegar, and dish soap solution. Disclaimer: I've not yet put the 3D version into field, so don't know if it'll work compared to paper method.