Ants are interesting creatures. Awful eye sight, great sense of smell, really strong in comparison to their body size and weight.
Ants also show up in literature. In The Once and Future King a young King Arthur is reduced to the size of an ant by Merlin so that he can learn all sorts of things like politics and leadership (who knew that giving in to Mordred, Arthur’s son/nephew by his sister Morgawse/Morgan Le Fey, when Mordred shows up looking for land whose inhabitants he can enslave could be a good thing. Neville Chamberlain fans take note).* Merlin transforms Arthur into a bird as well, but I just care about ants today.
In real life not only can ants lead lives of quiet desperation they also run the risk of becoming host to a nasty creature called the lancet fluke.
Fans of the movie Alien know that the nastiest thing about the alien was its gestation within a human host. The alien would go through an initial form that would impregnate a host and the bouncing baby alien would come out shortly after (hilarity ensues).
The lancet fluke is nowhere near as boring as the alien: impregnate the host, blow out its chest and run (yawn). In an interesting twist the lancet fluke does mind control (very high on the cool scale).
The terminal hosts are mammals like cows or goats, while the intermediate hosts are snails and ants. The terminal host excretes the fluke’s eggs during the process of…waste management, the eggs are promptly eaten by a snail (yes, I just used the words promptly and snail in the same phrase) where the eggs do a little bit of this and a little bit of that and eventually irritate the snails respiratory system enough to make the snail cough out the newly transformed fluke cysts into the outside world where they wait to be eaten by ants (who said the food chain was simple?).
Why would an ant eat the cysts? As it so happens the lancet fluke cysts coughed up by the snails are surrounded by a mucus that has pheromones that are appealing to the ants (yummy, tasty and sexy).
The interesting part is what happens after the ant eats the pheromone encrusted cyst. They become zombies. Literally, and only during the evenings (no coffins, however).
After an ant ingests the lancet fluke cysts the cysts open releasing flukes into various parts of the ants anatomy. A select group make their way to the ant’s nervous system and take over. During the day, the ant goes to work, tells jokes, has meals at home and pays her bills (males are typically around just to have sex with the queen and die. Oh, the good old days!).
At night, the ant finds that it has an uncontrollable desire to hang from the top of a blade of grass (why do I hear a Dane Cook joke in there?). It finds a comfy blade, climbs it and then locks its mandibles as close to the top as possible. And waits. What is it waiting for? The ant doesn’t know, but the lancet fluke does**: it is waiting to be eaten by some unlucky animal who will become the terminal host. Some cow, goat, or whomever, is going to come by, eat the grass, inadvertently eat the ant and by extension eat the fluke.
Why only at night? During the day, to paraphrase Ernest Hemingway, it is hot. The ant could die; the fluke cannot allow that to happen and so returns control of the ant’s brain back to the ant. The ant gets to run back to home and hearth away from the hot sun and make up excuses for missing dinner by admitting to fighting crime after work.
All that to ask the question: could there be an equivalent parasite in humans?
I first read about the lancet fluke in Daniel Dennett’s book Breaking the Spell: Religion as a Natural Phenomenon. Highly recommended.
Update (7/12/12): an interesting study on suicide in women linked to a cat parasite: http://vitals.msnbc.msn.com/_news/2012/07/02/12529379-cat-parasite-linked-to-womens-suicide-attempts.
* The Once and Future King is a wonderful book. I highly recommend it even as it takes the legend of King Arthur in directions I am sure the original mythologists hadn’t considered: like pacifism.
** I use the word know loosely. The lancet fluke has no brain. It’s behavior is purely mechanical. The various forms of the lancet fluke are executing genetic behavior that has survived over time and has allowed them to be fruitful and multiply. Kind of like us, only we call if free will.