Periodical cicadas: A tiny insect that can be as loud as 100 decibels 

Imagine an insect (identical to a bug) that is over an inch in length with a 3-inch wingspan, a black outer surface and an orange interior. It also has bright red eyes, and clear, membranous wings, having black veins. There, you have a periodical cicada! Apart from its colourful disposition, there’s something that’s sure to fascinate you. It produces a very loud vibrating noise, that too every 17 years. And, guess what? This sound is anything but pleasing. Yes, we are talking about periodical cicada here. 

Periodical cicada: The North American insect 
If we were told that we have to introduce cicada in a single sentence, we would say, it’s a small insect that is very loud. Now, are you wondering how loud can it really be? Well, it turns out, almost 100 decibels. No, this isn’t a joke. Maybe that’s why scientists often say that being near a cicada habitat and being next to a loudspeaker at a concert aren’t that different.  

Cicada is an insect that belongs to the superfamily of Cicadoidea and has two distinct characteristic features: small eyes that are wide apart on the head along with transparent well-veined wings. And the males of the species can cause a ruckus, although the females aren’t all that quiet either.  

Now, there are almost 3000 species of cicadas on this earth. However, there are 15 specific ones that are found only in the North American continent, and they are called as periodical cicadas (belongs to the genus Magicicada). Why? Because 12 of them arrive once every 17 years, while the rest 3, once every 13 years. And when they do arrive, they do so in large number, for a short period of time, and leave behind a long-lasting buzzing sensation. Okay, but where do they live when they aren’t really around? Well, of course underground! Interestingly, all the cicadas outside North America are annual ones, meaning they arrive every year.  

How do the periodical cicada make such loud noise? 
Turns out, a brood of adult periodical cicadas emerge once every 17 or 13 years and make incessant loud noise thanks to the presence of a vibrating membranes on their abdomens, that are in turn located on their wings. These help them make such a buzz. Scientists believe that they make such noise in order to invite their potential mates.  

But, why do emerge every 13 or 17 years? 
This one’s got to do with the life cycles of periodical cicadas. Let us dig deeper into it for a better understanding. As it turns out, the female periodical cicada lays as many as 400 eggs at a time. Now, as soon as these eggs hatch, young periodical cicadas called nymphs emerge and quickly burrow themselves underground. And they don’t come out until 13 or 17 years, that is, until they are fully-grown adults ready to defend themselves. Once they do come out, they do it in a synchronised giant swarm, which is when they end up annoying humans with their loud noise, primarily meant for mating (usually during springtime in the months of March and April). You may also find it interesting that during this time, periodical cicadas also molt, meaning they shed their exoskeleton (hard outer lining that provides both structure and protection). Maybe that’s why, if one looks closely, they will find that once the periodical cicadas depart, they leave behind an empty shell. Over the years, the scientist community has come to believe that arriving periodically not only helps these cicadas avoid predators and other dangers, but also have a more successful mating period. Interestingly, periodical cicada is also alternatively called Pharaoh cicada or the 17-year locust.