Under cover of darkness, a burrowing cockroach skitters across the desert sand. Its rapidly moving legs excite tiny ripples that travel along the ground, tipping off a lurking sand scorpion. Turning swiftly toward its prey, the scorpion darts forward with pincers outstretched, finally grabbing and stinging its victim.
How does the sand scorpion determine which way to turn? In effect, how does it figure out direction from waves traveling through the sand?