Eventually, they slow to an amble — a patrolling trot, Dean's eyes sharply scanning the planes stretching out before them as best he can through the waves of heat that distort what should be clear and flat.

"They travel in small packs. There's gonna be at least three or four of 'em. You'll see 'em kicking up a little dust, disrupting the earth, leaving trail lines. Cross between a scorpion and a snake, almost, the way they skitter-slither flat across the dirt." That's what he's looking for now. Dust trails. Moving lines. "When they stand upright... could be anywhere from two to eight feet tall, depending on how old we're catchin' em. Once they get big enough, we're talking full-on Tremors."

Pretty sure he doesn't need to say why they wanna catch 'em before that happens.