Periodical cicadas. John H. Ghent,
USDA Forest Service, Bugwood.org
Cicadas are divided into two main categories. Annual cicadas, whose lifecycle takes two to five years, appear every year. Periodical cicadas have lifecycles of 13 or 17 years.
Periodical cicadas belong to the genus Magicicada. All periodical cicadas of the same lifecycle length that emerge in the same year are considered part of the same brood. Broods are given Roman numerals to identify them. The brood emerging in New York in 2013 is brood II of the 17-year cicada. In 2014 brood XXII of the 13-year cicada will emerge in Louisiana and Mississppi and brood III of the 17-year cicada will emerge in Iowa, Illinois and Missouri.
There are seven species of periodical cicadas, four with a 17-year cycle and three with a 13-year cycle. The three species in each life-cycle group are distinctive in size, color, and song. The 17-year cicadas are generally northern, and the 13-year cicadas southern with considerable overlap in their distribution. In fact, both life-cycle types may occur in the same forest.
Magicicada adults have black bodies and striking red eyes and orange wing veins, with a black "W" near the tips of the forewings. Most emerge in May and June.
Annual dog-day cicada (Tibicen canicularis)
David Cappaert, Michigan St U, Bugwood.org
Annual cicadas require 2-5 years to complete a life cycle and rarely are abundant enough to attract attention, but because many broods overlap, adults can be heard every year. Some of the annual cicada species are sometimes mistaken for the periodical cicadas, especially those in the genera Diceroprocta and Okanagana; these other species emerge somewhat later in the year but may overlap with Magicicada.