We tested snakes in the lab, but tropical banana spiders act weird in captivity. You have to observe them on their own turf—the jungle at night. You shine a headlamp around, and their eyes reflect a blue sparkle. Then you tempt them with a tadpole on a stick and hope they don't run at you. They're massive—the size of tennis balls—and hairy, with venomous fangs. I keep 40 snakes in my office and don't scare easily, but something about the way these spiders move made me panic. I kept freaking out and accidentally throwing the bait tadpoles into the bushes. Eventually, I had to recruit students to help me.