After 17 years underground, the Brood X cicadas, also known as The Great Eastern Brood, erupted in the Midwest and Mid-Atlantic with their loud, buzzing sounds and vast numbers this year. And if you happen to live in one of the 15 states where they emerged, you might have seen them swarm houses, patios, trees, lawns — you name it. Check out the lowdown on these fascinating plant-hoppers, and the evolution behind this curious, insect-laden natural phenomenon.