"Saint Jude bless you fool, it's real an' it's hungry an' I ain't stupid enough to stick around an' get et."

Amos lets go of Josh's arm and grimaces at how the giant centipede is following them, at the click of the carapace echoing in the cavern, the musty scent of the thing, the way its mandibles click together. He can hear/feel/taste its hunger, and it's not a pleasant thing to stand so close to a large carnivore that ravenous and knowing you are prey.

"Move or die when the monsters come hunting, child."

That's the last bit of Advice Amos will give, hurrying around the next corner. He's in fear for his own flesh, and he's not self-sacrificing enough to try to pull Josh with him all the way.