Think your Uncle Ned has lousy table manners? The common house fly vomits on its food before consuming it! This is in so that acids in it's up-chuck can soften the food so it can be sucked up through it's straw like mouth. Want to know something even more horrible than that? Flies excrete digestive juices wherever they land as a means of testing whether or not what they've landed on is edible. Yuck!