|Periodic Cicada - Magicicada sp.|
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Live adult 17-year periodic cicadas and exuvia, Magicicada sp. brood XIII, 2007, photographed in the
wild at Lisle, Illinois.
17-year periodic cicada, Magicicada sp. brood XIII, 2007
A small number of cicada species have synchronized their life cycles so that they emerge from the ground in their billions only once in every 13 or 17 years. These are known as periodical cicadas but are also commonly called 17-year cicadas, 13-year cicadas, or locusts. They are not locusts, however. The dog-day cicada is dark with green markings. The periodical cicada has protruding red eyes and orange legs; adults have clear wings with orange veins .
It is not known how periodical cicadas synchronize their life cycles — or how they manage to count out the years. But by emerging at such long intervals in such vast numbers, as many as 1.5 million insects per acre, according to one estimate, they have evolved an effective strategy to overwhelm predators by sheer volume. The mass emergence of periodic cicadas provides an unlimited feast for birds, snakes, and mammals. Even humans have been known to eat the harmless insects (Cicadas are not poisonous and do not bite or sting).
Once the predators have eaten to capacity, there are still millions of cicadas left over to produce the next generation. Predator populations cannot build up in response to such a massive food supply, because the cicadas appear above the ground only once in every 13 or 17 years.
Periodic cicadas are found in eastern North America and belong to the genus Magicicada. There are seven species, four with 13-year life cycles, and three with 17-year cycles. The three 17-year species are generally northern in distribution, while the 13-year species are generally southern and midwestern. Periodic cicadas generally emerge in May and June, apparently when the soil temperature reaches 64° Fahrenheit (18° Celsius). This means that emergences in southern and low-lying areas occur earlier in the summer than in the cooler northern locations.
Magicicada cicadas synchronize their life cycles only in local areas. There are 12 broods, or year classes, among the 17-year cicadas and three broods of 13-year cicadas so that in almost any given year it is possible to find adult periodic cicadas somewhere in the U.S. .
Exuvia (plural: exuviae) (castoff skin after molting) includes exoskeleton
and coverings for the nascent wings, compound eyes, extremities, as well as setae.
1. Ralph Harbach, Mosquito Taxonomic Inventory, "cibarium"
2. Thomas Eisner, Maria Eisner, and Melody Siegler, Secret Weapons: Defenses of Insects, Spiders, Scorpions, and Other Many-Legged Creatures (Belknap Press, 2005).
3. Gary A. Dunn, Insects of the Great Lakes Region (University of Michigan Press/Regional, 1996).
Order Hemiptera: True Bugs number almost 5,000 species in North America, and 40,000 worldwide. They have mouthparts formed into a beak, adapted for sucking plant juices or the liquefied insides of their animal prey.
Suborder Auchenorrhyncha - Cicadas & Planthoppers
Suborder Sternorrhyncha - Aphids, scales, mealybugs, jumping plant lice.