Fruit Fly Trap (Customizable)

This is a small and simple design of a fruit fly trap.

The printed part simply gets screwed onto an empty jar, which has a luring liquid on the bottom. The flies get through the small slots into the jar and are unable to escape again. In addition this makes a great package for gift cards or money.

So don´t buy stupid cards or envelopes and hand over a real useful present.

It took about ten minutes to design and is a nice little example how effective parametric CAD design with FreeCAD is.

Well, the ten minutes is without getting the measurements and tolerances for the jar right. :D

By default this file fits onto LIDL discounter maribel jam jars. If you adapted this for other jars, send be the measurements and I will add them to this text.

Please note that the design is designed to avoid over tightening of the lid. It simply pops back to the previous winding. This is intentional. It wont fall of, when grabbed by the lid ether. Due the open fly trap slots it makes no sense to seal it with force like a jam jar.

However the FreeCAD file contains a spreadsheet with all required measurements, so you should be able to adapt the design to any jar in your household. There is no need to learn CAD to customize this thing.

In addition to that you can define the number of thread fingers the printed jar lid should have. You can also adapt the design to catch bigger flies by increasing the opening in the funnel as well as the number of openings.

Once printed just screw the lid onto the empty jam jar and you are good to go.

There are tons of recipes available online. Basically they all use vinegar, something sweet and a drop of dish washing liquid to break the surface tension of the liquid at the bottom of the jar.

The sweet component can basically anything a fruit fly likes. Apple juice or some putrid fruit. Wine or special vinegar works, too.

It is just important to give the trap some time. It may take up to 24 hours until the traps starts doing their magic. Make sure not to place the jar next to a window or heat source. Depending on the amount of liquid used and the ambient temperature, a change is needed once a week or every few days.

Placing it near locations where fruit flies lurk around is the key. So place the trap next to your kitchen sink or a fruit basket so the flies stay away from the good stuff.

Update: #1: I added a version with a more round lid.

Update #2: Added German LibreOffice file to print as how to use instructions.