Cicadas...

Cicadas are medium to large size insects. They can look big and menacing, but are completely harmless, and have absolutely no defense mechanisms. This makes them prey to literally every living creature on earth. They're literally at the very bottom of the food chain for anything larger or even smaller than them. Ants, spiders, and preying mantises love eating these guys, just as much as birds and mammals do. Across the planet, there are thousands of cicada species known to humanity to date. For this site, I will focus on some cicadas of the U.S. specifically. There are two types of cicadas in the U.S. These are annual cicadas, and periodical cicadas. Let's examine the differences...

Annual cicadas, are cicadas that are not synchronized with the rest of their kind, so some appear every year, or annually. These cicadas can emerge in decent, but not crazy overwhelming numbers like periodicals. You'll notice these guys and gals in the hot days of late spring and throughout summer across the U.S. The males will buzz in a mating call to females during the day, but mostly in the hot evening summer breeze. This will give us the classic sound of summer, that otherwise wouldn't be summer without right!? Annual cicadas are green and brown, but can also be black and orangish depending on the species. There's even a species that's body is lime green! So, they can pretty colorful! Annual cicadas are rather large, and definitely larger than any periodical species.

Periodical cicadas, are the special ones. This is for many reasons. They have synchronized, timed mass emergences, in which they will overwhelm nature and predators. They are colorful, with black bodies, yellow/orangish wings, and red eyes! They are oh so easily distinguishable from other insects when you're in the middle of a mass emergence. Periodical cicadas only exist from the mid-west to the eastern seaboard of the United States. They do not exist anywhere else in the world. These cicadas have evolved to segregate themselves into 15 different groups, or "Broods". Each group has its own timed cycle and has been given names by roman numerals. 12 of these 15 groups are on a 17-year cycle. Only 3 of these 15 are on a 13-year cycle. This means that in the area in which an individual group is present, every 13th or 17th spring, they will emerge in mass numbers to simply overwhelm predators. If their numbers aren't large enough in a particular location, they will not be able to survive. This is because their survival strategy is to simply overwhelm their predators. This is what is known as "Predator Satiation". There must be enough that survives predator attacks to keep the species going.

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Emergence...

In the spring of a brood's year, usually in April, Periodical cicada nymphs are just below the surface waiting for the surface temperature to become warm enough for them to emerge. You can notice these guys on the forest floor during this time located in numerus holes they build in preparation for their arrival.  

When the ground and the air temperatures have warmed consistently and sufficiently, the brood emerges over the course of a couple weeks, with 2 or 3 nights of a mass emergence. This usually happens in mid-late May. You can find nymphs emerging at night on trees, or any other vertical surface they can grip to. At this time, they are looking for a spot where they can securely grip their six legs to for the molting movements to come. Below, I have attached a clip of a timelapse of an annual cicada molting from last summer. The process is the same for periodicals....

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The mating chaos and purpose...

Individual males will make a pretty loud call, by using an organ called a "tymbal". Males have 2 of these on either side of their abdomen. Males will produce what is known as a "chorus" when there are many (uncountable numbers) calling at the same time. Females lack this organ, so they cannot make this sound. They do, however, respond to male calls when they show interest in mating by flicking their wings. It is literally a frenzy chaotic scene in the trees and woods they inhabit for a few weeks. Their sole purpose is to simply mate and reproduce. They will accomplish this in a matter of 3-5 weeks from May - June of a group's (or broods) year. When mating is complete, the males will die first, and females still have to lay their eggs. An individual female can lay up to a few hundred eggs at one time. She uses a sharp needle structure called an "ovipositor" from her abdomen, to slice into branches of trees, and insert eggs into them. When this act is complete, everyone dies. The woods are left with rotting shells and adults for the rest of the summer, reminding everyone of the memory of their existence. The tiny nymphs will hatch from the eggs that were laid in the branches in August, fall to the ground, and borrow under the soil. They will mature and grow as they feed on tree or shrub roots for 13 or 17 years. The cycle will repeat itself all over again in the next generation.