Hey,
mr_rubix, guess what?
The Great Fruitfly Mystery (TM) has been solved. And you totally called it. Hidden rotten potato ftw! Fuck you, Drosophila melanogaster! You die now!
EDIT: Ok, so it has been suggested by a certain ornery roommate that I clarify that the nasty fruitfly nest was only found because of a comment from
bumpercub about them possibly coming from a water leak under the sink. Fine, fine, credit given where credit is due.