Adam and Caveman Rob take on America’s biggest and most deadly scorpions. But their surprising result is a hugely painful wake-up call–and a new Scorpion King is crowned.

Adam has a phobia of tarantulas, so naturally Caveman Rob picks two of the world’s nastiest ones for them to endure, including a tarantula with the well-deserved nickname: “Orange Bitey Thing”.

Adam and Caveman Rob get bitten by one lizard whose venom is in doubt–but not its ability to latch on and tear flesh–and another whose venom is notoriously painful. The shocking results set new records for the Pain Index.

In a tribute to the godfather of the Pain Index, Dr. Justin Schmidt, Adam and Rob tangle with a new batch of extremely painful–and deadly–insects. And one colony of ants kicks the Schmidt out of them.

Adam thinks he’s getting his revenge on Rob for selecting tarantulas earlier this season by programming Rob’s phobia: centipedes. But the joke is on Adam when an American centipede produces one of his most painful bites ever.

Some of the most painful animals can be found in your very own backyard. Rob and Adam take on an Assassin Bug, a Jerusalem Cricket, and the Brown Widow Spider–producing a record-setting episode of pain.

Rob and Adam test the pain dished out by a trio of unlikely creatures commonly kept in home aquariums–and they proceed to ruin the image of a popular cartoon movie character for millions of children.

Rob and Adam test the Yellow Head Moray Eel for possible venom effects, but must resort to a risky, bloody bite. But venom is not the issue for their next animal: the Electric Eel. The results are positively shocking.

It's America vs Australia in a battle royale of pain administered by sharks. After getting stung by both, Adam and Rob realize that when their countries win, they lose.