Want a Cozy, Free Home? Ask This Caterpillar How

Watch turret spiders, wormlions, assassin bugs and dragonfly babies use stealth, speed and lethal weapons to dispatch their prey.

As a caterpillar, a grass skipper butterfly is an architect. It builds its home by weaving silk, which the caterpillar uses to fold shut a blade of grass. After growing up inside this “grass taco,” it emerges as a fuzzy butterfly that woos a mate with flirty courtship dances.

Known as sand piranhas, Excirolana chiltoni are tiny crustaceans that nibble at your feet – and draw blood – if you hang out on the wet sand at the beach. They live on the Pacific coast of the U.S. and Canada, and the shorelines of Japan. Here's how to keep them from ruining your vacay!