Last week I was on vacation in Connecticut, and somebody left the patio door open for a few hours. Pretty soon the kitchen was filled with about 50 huge, fat, disgusting flies, and I was left with the even more huge, fat and disgusting task of running around killing them all with a rolled-up newspaper. And of course, I quickly discovered something everyone has figured out: Flies are really good at avoiding a swatter.

How do flies do it? Scientists and chefs have argued about this for years. Some theorize that the flies can sense the approaching air shock wave generated by a rolled-up newspaper. But nobody ever really knew. So a group of US scientists led by Caltech’s Professor Michael Dickinson decided to swat at some flies while filming them in super-slo-mo. According to the BBC …

… the researchers discovered that long before the fly leaps it calculates the location of the threat and comes up with an escape plan.

Flies put their bodies into pre-flight mode very rapidly: Within 100 milliseconds of spotting the swatter they can position their centre of mass in the right way so that a simple extension of their legs propels them away from any threat. [snip]

“Our experiments showed that the fly somehow ‘knows’ whether it needs to make large or small postural changes.

“This means the fly must integrate visual information from its eyes which tell it where the threat is approaching from, with mechano-sensory information from its legs, which tells it how to move to reach the proper pre-flight pose.”

So: What advice are we to glean from this? Unfortunately, Dickinson suggests that to kill a fly you should “aim bit forward of its location and try and anticipate where the fly will jump when it first sees your swatter,” which seems kind of nuts: What sort of crazy latent ninja abilities do you need to harness to anticipate where a fly is going to jump?

Even funnier is that BBC video of the fly-recording experiment, because the BBC bills it as “high resolution video of a fly avoiding a swatter”, but when you click on it you’re first subjected, without warning, to a 30-second long tourism ad for the city of Seoul. So when I clicked on it and found myself watching a long panning shot of some Korean dude wandering around downtown Seoul, doing some shopping, eating dinner, I thought, wow, this is one seriously sophisticated fly.

UPDATE: James Sherrett stopped by to post a totally awesome guide to fly-swatting, based on his summers gutting fish — a necessarily fly-infested task — in Northern Ontario. Go check out the comments to read it!