What Would Happen If You Ate Something A Fly Landed On?
This is What Would Happen If, a close examination of mundane hypothetical situations. Each week, we look at something that you could do but probably never would, and take it to its logical endpoint. This week: What would happen if ate something a fly landed on?
Where there are humans there is trash. And where there is trash there are flies. Such is the way of the world. Sometimes, a fly will mistake your food for trash — the distinction, sadly, is lost on them. Sure, you manage to shoo it away, but what the heck did this fly just do? And more importantly: Is it still cool to eat this food?
To arrive at something resembling a useful answer, we must understand the fly. To do that we spoke with Robert DeSalle, the curator of entomology at the American Museum of Natural History. He understands the fly, and it is his wisdom that will help guide your thinking when it comes to eating stuff that has been touched by a fly.
So, what exactly happens when a fly touches down on that thing you're about to ingest? As much as you want to believe it, the fly is not looking for a rest. The specifics depend on the type of fly, but generally, you're looking at trio of possibilities: they're eating the food, contaminating the food or impregnating the food. If you're extremely lucky, it might be doing all three!
So: Eating. Flies do not take bites out of your food. That's not how their mouths work. In order to consume food, flies must do some combination of spitting up and slurping. Houseflies, for example, don't have mouths so much as they have a mouthparts that sponge up liquid. If the food you're about to eat has some surface moisture to it, then the fly will just plop down their mouthsponge (the scientists call this a "labella") and get to absorbing — which it will then fly away, puke up again with some digestive enzymes and then slurp back up. If the food is a little more solid — like, say, a piece of meat — the fly might first puke up some of its digestive juice, just to soften things up enough to slurp up.
A fly trying to eat your hot dog is not disgusting because a fly must use a flesh sponge to consume nutrients. A fly trying to eat your hot dog is disgusting because a fly carries bacteria.
Flies love to spend time around rotting food and other waste products. "They can carry a lot of bacteria on their legs and mouthparts," writes DeSalle. He is loathe to point out that recent studies suggest that flies are carrying more bacteria on their legs these days "than usual." So, if a fly even lands on your food, there's a very good chance so will the pestilence that it carries.
What's less clear is what might happen if you eat that food. Flies definitely carry bacteria, but it's hard to say exactly what kinds. "One could get sick from ingesting the bacteria just like eating any contaminated food," writes DeSalle. "There are also some flies that carry nasty diseases around with them like TseTse flies."
In addition to unintentionally depositing bacteria, flies will also intentionally lay eggs in food. It's not exactly an immediate risk if you're about to eat the food, but if it's something that's going to sit on the counter for a day or two, well, it's not good. "If a fly landed on a piece of meat, and you let it sit for a day or two, chances are several if not a horde of maggots would appear soon," writes DeSalle. Granted, he points out that grubs and maggots are found in plenty of food cultures around the world. That said, he has his reservations. "If you eat meat with uncooked maggots in them, it would probably taste pretty bad," he writes. "I don't know if you would get sick. But it would be pretty gross."
The bad news is that a fly will probably deposit something not cool on your food. The good news is that because it's just a fly, the nastiness is only limited to the surface. DeSalle says that cooking the food will be enough to kill any foreign bacteria or eggs. So if it lands on a hot dog or burger, just throw it back on the grill real quick.
As for the ultimate question of "Is it cool if I just shoo the fly away and eat the food?" Well, DeSalle is pretty unequivocal about that: "If it is a horsefly or a large house fly I would simply throw the food out." Well that about wraps it up folks. If the scientist is telling you not to eat something a fly lands on, maybe you should listen to him.
On the question of whether or not you should dump out your glass should a black fly land in your chardonnay, well, DeSalle is a little more optimistic. "These smaller flies while they do transport bacteria around carry so few microbes that a quick guzzle of alcohol and your stomach enzymes probably take care of most of the bacteria." Now isn't that ironic?
