As the name implies, these cicadas emerge only at certain times. These cicadas mature underground at depths of up to 2 feet. Different species of periodical cicadas emerge at different intervals. In Missouri, for example, periodical cicadas emerge every 13 and 17 years. Whatever the time frame, the adults emerge from the ground on schedule, usually in May and June. Annual cicadas, on the other hand, emerge from the ground every year in the latter part of summer. Although the large number of periodical cicadas may seem threatening, the risk of damage to plants and trees is small. Most damage occurs when too many cicada eggs are laid on branches, which can cause problems for younger trees. Periodical cicadas are only found in North America.