It's happening! Cicadas are emerging. Have you spotted any? There are many sites that track the sightings. It's still early, but if you are expecting the brood to emerge, the countdown has begun! You can follow along here!
Periodical cicadas achieve astounding population densities, as high as 1.5 million per acre. Densities of tens to hundreds of thousands per acre are more common, but even this is far beyond the natural abundance of most other cicada species. Apparently because of their long life cycles and synchronous emergences, periodical cicadas escape natural population control by predators, even though everything from birds to spiders to snakes to dogs eats them opportunistically when they do appear. Magicicada population densities are so high that predators apparently eat their fill without significantly reducing the population (a phenomenon called "predator satiation"), and the predator populations cannot build up in response because the cicadas are available as food above ground only once every 13 or 17 years. Read more here.