Sometimes during the summer time the kids forget to eat an apple or some other fruits, soon after this you have this little fly's that are really annoying.
Now just print the two parts fill them with
-vinegar up to the first mark
-fruit juice up to the second mark
-water up to the third mark
and give a few drops dish soap into it.
Mount the thing together and wait ;).
Best color to print is yellow as the flys being attracted to this color.