This spring the American Midwest and South will experience a numerically magnificent wildlife event: a rare double emergence of periodical cicadas. With the arrival of Brood XIX and Brood XIII, trillions of harmless insects will be singing their hearts out from Wisconsin to Louisiana, Maryland to Georgia. The last time these broods co-emerged was 1803. As impressive as that is, this year’s entomological phenomenon is special for researchers hoping to unravel the evolutionary mysteries of bugs that crawl out of the ground in roughly 13-year and 17-year intervals. Broods are not the same as species, and each brood can contain multiple cicada species that can emerge in different places. In 2024, all seven cicada species will be represented, a coincidence that won’t happen again until 2037. …One of the more unusual mysteries scientists hope to investigate involves a parasitic fungus that attacks adult cicadas, turning them into what one expert calls “flying saltshakers of death.”