1The day starts normally enough.
2You give your pet some food and water.
3But later...
4in your pet's water dish, you find this.
5A hairworm.
6It didn't get here on its own.
7It came out of a little cricket.
8Don't believe me? OK.
9These hairworms are gnarly parasites.
10They actually control a cricket's mind to get to their home: the water.
11The hairworm's journey starts innocently enough, in a river, as an egg...
12one of many in this long string.
13The eggs grow into squiggly larvae,
14which get eaten by a mayfly larva that also lives in the river.
15And inside the mayfly is exactly where the hairworm needs to be.
16The hairworm uses this pointy part to burrow into the mayfly's flesh.
17Then it curls up and waits.
18Because, really, it's not after a mayfly.
19It's after a cricket.
20So it sits tight, while the mayfly larva turns into an adult and heads to dry land...
21where it just might get eaten by a cricket...
22that has no idea what it's in for.
23Inside the cricket the hairworm goes at it,
24eating all the cricket's stored-up fat, for about a month.
25The cricket loses its chirp,
26but the hairworm doesn't kill the cricket...
27because the worm needs a lift back to the water.
28Crickets usually avoid bodies of water.
29They're not great swimmers.
30So the worm takes over,
31boosting chemicals in the cricket's brain,
32which make the cricket walk around mindlessly until it happens to reach water.
33Scientists in France watched this infected cricket make a beeline for the pool.
34The hairworm makes a break for it.
35Still going.
36Ugh, that's just... ugh.
37But don't worry.
38They don't target humans.
39Ready for more?
40This one at the University of New Mexico... has a whole lot of hairworms inside it.
41They don't waste any time, curling around each other to mate...
42even before they're fully outside the cricket.
43But it's more than a gruesome spectacle of nature.
44Learning about these hairworms could help scientists understand parasites like toxoplasma that make us very sick.
45As for the crickets, don't feel bad.
46If they don't drown, most of them survive their ordeal.
47At least that's what scientists have seen in the lab.
48They go back to being crickets and hopefully stay on dry land.