For what I am doing, I do not understand. For what I do not wish to do, that I do; moreover, what I hate, that I do. If, then, I do what I do not wish to do, I agree with the Law that it is good. But now, it is no longer I doing it, but sin that dwells in me.

– Romans 7:15-17 (VW)

Paul struggled with sin, even after he was saved. He wanted to do good by obeying the Law, but he found he was not able to. No matter how hard he tried, he kept doing what he didn’t want to do. It was like he had two natures: one that rejoiced in God’s law, and another that held him hostage to things he now found abhorrent.

Paul was not making excuses for his sin when he said, “It is no longer I doing it, but sin that dwells in me.” He was admitting there was something in him that prevented him from obeying God. It was like he was possessed, …not by an evil spirit, but by his old sin nature. There’s an interesting picture of this in the life cycle of the lancet fluke.

The lancet fluke (dicrocoelium dendriticum) is a parasite that infects different creatures at different stages in its life. Adult lancet flukes live in ruminant animals such as sheep or cattle, but how they get there seems like something out of a budget horror movie.

An adult fluke lays eggs in the bile ducts of its host. The eggs move to the intestines and then leave the animal in the droppings. The eggs remain unhatched until a particular variety of snail ingests the droppings. Once inside the snail, the hatchlings (mericida) replicate into many more sporocysts, and then into larvae called cercariae. These larvae eventually migrate to the snail’s respiratory system where they produce slime balls. The snail sheds these slime balls and larvae as they move along.

Now remember, the adult lancet fluke lives in a cow or sheep. How do the larvae make their way back into these animals so they can complete their life-cycle? I’m glad you asked!

Along comes a particular variety of ant looking for a source of moisture. It finds a larvae-infested slime ball, and eats it. And this is where things get weird.

Inside the ant, the larvae again transform into hundreds of metacercariae that live in the ant’s gut. But after living there for some time, a single metacarcaria leaves its siblings and heads for the ant’s sub-esophageal ganglion where it takes control of the ant’s actions. The ant is now a zombie, unable to function as a normal ant.

During the day, the zombie ant appears to act like a normal ant and works with the other ants. But in the evening, the zombie ant leaves the others, climbs to the top of a blade of grass, and holds on to it with its jaws all night until morning. It then returns to its fellow ants for the rest of the day as if nothing happened. The next evening and the next, it climbs to the top of a blade of grass, until a chance cow or sheep comes by, eats the grass with the ant, and returns the parasite back to a large host. It then fully matures, mates, and produces eggs, closing the cycle of life.

Does the zombie ant truly want to get eaten? Of course not. But it can’t help itself. It is no longer the ant doing what it wants to do, but the lancet fluke that dwells within dictating what the ant’s actions. (Here’s a cartoon version of this cycle.)

I see in these zombie ants a picture of ourselves when we allow our fallen nature to control our thoughts and actions. The illustration isn’t perfect, as the whole human race has been infected since the fall, but it’s close enough. When Jesus saved us, He gave us His Holy Spirit to overcome our sinful fallen nature. But we need to give Him control instead of letting our little parasitic nature run our lives. Like the lancet fluke’s control of the ant, allowing our sin nature to run things leads to death, but letting the Holy Spirit run things leads to life.