1We like to think we're in control...
2that our minds are our own.
3But that's not true for this fruit fly.
4Its brain has been hijacked by another organism
5and it's not gonna end well.
6It all starts when the fly is innocently walking around,
7sipping on overripe fruit.
8It picks up an invisible fungus spore,
9which bores under its skin.
10For a few days, everything seems normal.
11But inside, the fungus is growing, feeding on the fly's fat...
12and infiltrating its mind.
13At dusk on the fourth or fifth day, the fly gets a little erratic, wandering around.
14It climbs to a high place.
15Scientists call this behavior "summiting."
16Then it starts twitching.
17The fungus is in control.
18The fly sticks out its mouthpart and spits out a tiny drop of sticky liquid.
19That glues the fly down, sealing its fate.
20A few minutes later, its wings shoot up.
21And it dies.
22Now that the fungus has forced the fly into this death pose... wings out of the way...
23nothing can stop it.
24It emerges.
25Tiny spore launchers burst out of the fly's skin.
26Hundreds of spores shoot out at high speed,
27catching a breeze if the fly climbed high enough.
28They're the next generation of killer fungus.
29It continues for hours, spores flying out.
30These flies are in the wrong place at the wrong time.
31And if spores land on a wing,
32which they can't bore into,
33they shoot out a secondary spore to increase their chances of spreading.
34So how does a fungus take control of a brain?
35At Harvard, Carolyn Elya is trying to understand that.
36She thinks the fungus secretes chemicals to manipulate the fly's neurons,
37maybe stimulating the ones that make flies climb.
38But don't worry: the fungus can't hurt humans.
39Scientists have tried to harness its power for our benefit,
40to kill flies in our kitchens and farms.
41They haven't had any luck though.
42The deadly spores are actually pretty fragile and short-lived.
43It turns out, this lethal puppet master does only what it needs to for its own survival.