The insects are expected to appear throughout the Midwest and Southeast in early May, in a double appearance. This year's appearance is expected to be unusually large, with some experts estimating that more than a billion cicadas could cover parts of the country where the two broods overlap.
For cicada enthusiasts, it is a once-in-a-lifetime opportunity to experience the co-appearance of the two cicado appearances, as the last time it occurred was in 1803, when Thomas Jefferson was president. “It's something no one has ever seen and that no one will ever see again,” says one expert. The mating song of these insects, a high-pitched drone, is difficult to ignore and can reach almost 100 decibels. The insects are harmless to humans, although some people are bothered by the large number of insects and their strident mating songs. In North America there are seven broods of periodical cicados that, depending on the type, emerge every 13 or 17 years.