13 or 17 Year "Locust"?
|2011||Great Southern Brood (Marlatt's XIX)||13|
|2014||Iowan Brood (Marlatt's III)||17|
|2015||Lower Mississippi River Valley Brood
|2020||Northern Illinois Sub-Brood
(part of Marlatt's XIII)
|2021||Great Eastern Brood (Marlatt's X)||17|
|2024||Northern Illinois Brood (Marlatt's XIII)||17|
The periodical cicada emergences are composed of three distinct species. Some experts consider the three species that occur in 13 year emergences as different from the three that occur in 17 year emergence, but others do not. Thus, depending on the expert, there are six or three species and each species vary from each other in size, color, and song. These species are further divided into broods, referring to the year and geographical area where they emerge. Some broods are small and cover a limited area. Others are very large and emerge across many states at about the same time. There is a brood emerging somewhere every year. The periodical cicadas found in Illinois tend to be dark brown and black on top with lighter reddish brown patterns at the wing bases. The lower body color is similar to the wing bases. Compound eyes are red with orange major veins in the membranous wings.
The northern Illinois brood, which will emerge in late May 2024, has a reputation for the largest emergence of cicadas known anywhere. This is due to the size of the emergence and the research and subsequent reporting over the years by entomologists Monte Lloyd and Henry Dybas at the Field Museum in Chicago. During the 1956 emergence, they counted an average of 311 nymphal emergence holes per square yard of ground in a forested floodplain near Chicago. This translates to 1½ million cicadas per acre. In upland sites, they recorded 27 emergence holes per square yard, translating to about 133,000 per acre. This number is more typical of emergence numbers but is still a tremendous number of insects. For comparison, a city block contains about 3½ acres. When the cicadas start dying and dropping from the trees later in the spring, there are large numbers on the ground, and the odor from their rotting bodies is noticeable. In 1990, there were reports from people in Chicago having to use snow shovels to clear their sidewalks of the dead cicadas.