Old World Swallowtail Papilio machaon

As the founding species of the largest butterfly genus on Earth, this butterfly holds a unique place in the history of natural science. The genus Papilio contains over 200 species, all formally anchored to this single "type species" — meaning it set the standard by which every other member of the genus is defined. Found everywhere from British fenland to Arctic tundra, it's one of the most widespread butterflies in the Northern Hemisphere.

Threaten a caterpillar and it deploys the osmeterium — a forked, bright orange organ that erupts from behind the head and releases a pungent chemical smell, mimicking a snake's tongue to startle and repel predators. It's one of the most dramatic defensive displays of any caterpillar, and it works remarkably well.