This Is What a Cicada Orchestra Sounds Like
This fall, Center Theatre Group audiences are being treated to an accompaniment that’s unfamiliar to many Angelenos: a chorus of cicadas. These insects provide the soundscape for the Arkansas-set Appropriate, which plays at the Mark Taper Forum from September 23–November 1, 2015. But how exactly do the cicadas make their music? The Natural History Museum of Los Angeles County’s Lila Higgins explains here.
Si-KAY-duh or si-KA-duh? What we call these soniferous insects (si-KAY-duh is more common) has got nothing on how they call each other. The sounds of the cicada range from buzzing pulsations to whining drones. At first listen, they’re not that different from the sounds crickets and katydids make by rubbing their wings together, or what grasshoppers do by rubbing a hind leg on a wing. But cicadas don’t rely on appendages for their instrumentation. Instead, they come equipped with two specialized drum-like organs located on underside of their cylindrical abdomens—tymbals. Like the traditional human drum with a wooden frame and an animal skin head stretched over the top, cicadas’ tymbals consist of a hollow internal cavity covered by a membranous exoskeleton. Intricate corrugations (wrinkles) in the exoskeleton create areas of thicker and thinner membranes. Internal muscles pull on these corrugations and vibrate the thin membranes in between. The insect’s body becomes a sound box that amplifies the resulting noise. Cicadas have been recorded producing sounds of up to 106 decibels—imagine standing three feet away from a power mower. They are literally the loudest insect noisemakers on land (there is a louder aquatic insect that uses its male sex organ to make sound)!
But why?
Cicada music is all about mating, and it’s the males that do all the noisy work. Whether the sounds come from a scissor-grinder cicada, Neotibicen pruinosa, from the East Coast, or the largest cicada in the world, the Malaysian emperor cicada, Megapomponia imperatorial, they are all trying to attract a female of their own species. That’s particularly tricky because there are over 3,000 cicada species in the world. Most cicadas have reproductive organs that fit like a lock and key—only individuals of the same species will fit together. However, there are some cryptic cicadas that could fit with other species, and their songs are the only thing that distinguish them. To find a compatible mate, male cicadas produce a distinct call to ensure the right female is attracted. In some species, males try to increase their chances by forming massive aggregations, sometimes numbering into the thousands. Together, they can create a cacophonous chorus that is more likely to attract a slew of eligible bachelorettes, but there is also safety in numbers. Predators can hear those calls too!
Female cicadas do the heavy listening. Using another specialized organ, the tympanum, they can hear the vibrations from a male and hone in on his location. (Males also have these listening organs, and can actually disable them when they are singing their 100+ decibel songs.) When a pair of cicadas finally meet, the two continue to communicate through sound. Female cicadas flick their wings, sending cues as to their receptiveness to mating. In some species, the male cicada will then change his tune, picking from a repertoire of songs. A courting song will show his virility and hopefully convince a female that mating is the next course of action. An alarm call may be needed to warn of nearby predators. And if a male is successful in his reproductive attempt, he might employ a triumphal song in celebration.
If mating is the victory, the eggs are the prize—neatly packaged masses of genetic material are deposited into branches or bark. Using a specially adapted sword-like egg laying device, the ovipositor, the mother ensures the offspring are well hidden from predators. Within the vegetative nest, the eggs develop and hatch. Immature cicadas fall to the ground and use their specially adapted digging front legs to excavate a burrow. Underground, they live off plant juices, which they extract from roots with their piercing, sucking mouthparts. Some cicadas stay underground for a year and promptly emerge the next summer, while others stay underground for 13 or even 17 years. Mass emergences of periodical cicadas are always big news on the East Coast, with thousands of individuals crawling over every surface, singing from the trees and eventually littering the ground with their spent bodies.
Here in Los Angeles, we seldom hear cicadas. A handful of species live in the area, but they are hard to find. Wide-headed cicadas, Platypedia laticpitata, live in our local mountains and are a bit of an anomaly in the cicada world. Their sound-producing organs are so reduced in size that they no longer work. Instead, the male acts like a female cicada and bangs his wings together to produce a short, sharp clicking sound.
So listen up, audience members, as you head into the Mark Taper Forum this fall. Sure, the conversations among the human characters in Appropriate are going to be pretty dramatic. But the sounds of the cicadas most definitely will have love, life, and death hanging in the balance.