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Cicadas

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Male dog-day cicadas are out singing their songs and serenading the ladies. The males produce the characteristic shrill “singing” through the use of internal muscles and membranes within their mostly-hollow abdomen which amplifies the sound. The females don’t sing, but they can produce a noise with their wings that sounds like a light switch being flipped. The adult dog-day cicada is black and green with a flat, broad head and transparent wings. The nymphs develop in the soil and feed on plant roots for about a year. The nymphs only leave the ground to molt into an adult, leaving behind a characteristic cast skin that you’ve probably seen in your own yard. Despite their large numbers, cicada nymphs cause very little damage to trees and plants.

Periodical cicadas are black with red eyes and spend an inordinate amount of time in the nymphal stage. They stay in the ground for 13 to 17 years, and then emerge all at once. Their emergences are predictable enough that the broods are numbered and their year of emergence is known. For example, the great eastern brood, called Brood X, last emerged in 2004 and is expected to emerge again in 2021 in several eastern states to include parts of Georgia and Tennessee. The great southern brood, Brood XIX, is scheduled for 2024 in Alabama, Georgia, and Tennessee. Mark it on your calendars!

Cicadas emerge in staggering numbers. Their emergence is timed, with the majority of cicadas emerging within the same day or week. The purpose of their synchronized emergence is simple – predator satiation. Cicadas are delightful prey animals without distasteful toxins to protect them, and so they make a hearty meal for predators. Even if all the predators in the vicinity were to descend upon the cicadas and eat their fill, there would still be cicadas left to mate and reproduce. Fish, frogs, lizards, mammals, and birds change their hunting habits when cicadas emerge - it’s like an all-you-can-eat buffet for predatory animals.

People sometimes refer to cicadas as locusts, but locust is more correctly used as a designation for several species of grasshopper. When I lived in Arkansas, cicadas were called jarflies. Apparently, some people call them harvestflies – I guess it depends on the region. Regardless of what you call them, you know what they are as soon as you hear them.

Some species of cicada sing in a pitch so high that humans cannot hear them – we perceive their singing as silence. However, the cicadas that sing in a pitch we can hear are quite loud, and being in very close proximity to a singing cicada can actually cause permanent hearing loss. They sing at 120 decibels and are among the loudest of the noise-producing insects. In comparison, normal conversation is about 60 decibels, heavy traffic is about 85 decibels, and firecrackers and firearms are about 150 decibels. You’re not likely to be so close to a cicada as to cause hearing loss – most people would walk away from such an unpleasant cacophony. And rightfully so, if just to spare your ears.

References:
Noise-Induced Hearing Loss. National Institute on Deafness and Other Communication Disorders (NIDCD). Website: https://www.nidcd.nih.gov/health/noise-induced-hearing-loss. Accessed July 2017.