Periodical vs. Annual
Most species of cicadas have short life cycles, between two and eight years. Even though they have multiple-year life cycles, they are called “annual” because those cycles are staggered, so some emerge every year. They are also referred to as “dog-day” cicadas because the adults appear in July and August.
Annual cicada adults (Tibicen) are typically between 2 and 2.5 inches with brown or green markings and dark eyes.
Some annual cicada species are sometimes mistaken for periodical cicadas, especially those in the genera Diceroprocta and Okanagana; these other species emerge somewhat later in the year but may overlap with periodical cicada emergences. The Okanagana species are the most potentially confusing because some have coloration similar to periodical cicadas.
A small number of cicada species have synchronized their life cycles so that they emerge from the ground by the billions only once every 13 or 17 years. These are known as periodical cicadas (Magicicada). They emerge in May and June.
Periodical cicadas are found only in North America.
Periodical cicada adults are roughly 1.5 inches long with black bodies and striking red eyes and orange wing veins, with a black "W" near the tips of the forewings.
Some periodical cicada experts believe that there are seven total periodical species: four with 13-year life cycles and three with 17-year cycles. The three 17-year species are found generally in the northern part of the U.S., while the 13-year species are generally southern and Midwestern. Other experts believe that there are really only a total of three species and that the 13- versus 17-year cycles are genetically controlled.
There are twelve groups, or “broods” of periodical cicadas found in different areas of the northeastern U.S.
In the Chicago area, we encounter 17-year species dubbed “Brood XIII” (that’s Roman numeral 13). The species in Brood XIII include Magicicada spetendecim, Magicicada cassini and Magicicada septendecula. Brood XIII last emerged in our area in 1990 and is expected again in late May or early June 2007.
Cicadas Are not Locusts
Many people mistakenly use the name “locust” to refer to cicadas. The term “locust” was first mistakenly used to describe cicadas around 1715 in the English colonies, when settlers tried to make sense of the cicada emergences by equating them with Biblical plagues.
Cicadas belong to the order of insects called Homoptera. This order consists of plant-feeders characterized by stiff sucking mouthparts, four wings, and simple metamorphosis. Some other insects in this order are leafhoppers and aphids.
Locusts, on the other hand, belong to the order of insects called Orthoptera. This order consists of plant-eaters characterized by chewing mouthparts, two wings, and the ability to create sounds by rubbing two body parts together (which is different than the way cicada produce sound with their drum-like membrane). Some other insects in this order are grasshoppers, katydids, crickets, mantids, and walking sticks.
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