Fruit flies are a science teacher’s nightmare. They’re a classic study for genetics- short life span, only six chromosomes. The trouble is, no matter what you do, somehow, someway, the darned things get loose. Fruit flies. Everywhere. They breed like, well, flies, and aren’t nearly as selective about diet as the name would suggest.
A fruit fly infestation is hard to get rid of, because total removal of food sources is difficult. However, the combination of fruit fly trap and removal of food sources does prove effective.
While they have a surprisingly varied diet, they do prefer fruit. Like many animals that eat fruit, they’re attracted to the smell of fermenting fruit. The bait, then? Apple Cider Vinegar.
What makes your cup (disposable- easier to throw the whole thing out that way) into a trap? That’s the drop or two of soap you add to it.
Fruit flies are tiny and attempting to land on the surface of apple cider vinegar wouldn’t normally pose much in the way of problems. Soap disrupts the hydrogen bonds between water molecules, which in this case means it disrupts the surface tension. A classic classroom illustration is pepper floating on the surface of water. A drop of soap and it sinks.
So, apple cider vinegar for bait. Soap to disrupt the surface tension so they fall through and drown. Then, wait a few days. Fruit flies have short life expectancy, and you want to catch all of the newly emerging adults as they hatch as well. An effective trap, and an infestation removed.
Trego's Mountain Ear 