We take every thought captive to obey Christ. - 2 Corinthians 10.5

Parasitoid wasps are a thing. 

It appears that they roofie other bugs and turn them into a living incubator for the wasp's eggs - which hatch into larvae and devour their host then bust out like high school football players through a blast sign. Gross, huh? (Yeah, but at least one of 'em does it to cockroaches, so it brings balance to the force.) This appears to have been going on for forty million years, if you believe what the scientists say about the fossil evidence. 

Think about that: a hostile, alien being that hijacks the brain, making a creature cultivate the means of its own destruction. 

Paul knew all about this. That's why he declares in 2 Corinthians 10.5 that he "takes every thought captive." He deploys the same Greek verb he uses in Romans 7.23 to speak of  seeing "in my members another law. . . making me captive to the law of sin that dwells in my members." For Paul, this is war. "Damn the mosquitoes! Full speed ahead!" (Sorry. "Wasps" doesn't make the pun.) 

The devil is a parasitoid insect who co-opts us as surrogate wombs to nurse our own destruction. The good news is that we can choose other roommates. "The peace of God," promises Philippians 4.7, "which surpasses all understanding, will guard your hearts and your minds in Christ Jesus."

I have a friend who is a ventriloquist. When she makes a mistake in her routine, she manipulates the puppet so that it turns slowly toward her and eyes her before asking, "Who's working your head?" It's a pretty good question.