Another very important thing to reduce the escaping risk (C. vagus is a real escapologist!
), is to create an horizontal edge over the top, where you can put the mixture underside. You can cut the box covering cap or something similar, just to make a border on which an ant needs to walk upside down: in this way the slippery and horizontal but reversed surface becomes near impossible to cross... ...sometimes C. vagus workers finds some smart cooperative way to cross even in that case, but it's a matter of very huge numbers (old colony problem) or unexpected issues as a not too large border!
So don't you worry, your little colony is still easy bearable.
