From North Carolina northward to Maryland, Brood II cicadas are now up in the treetops chorusing to win the affections of their mates. In previous episodes we learned about the cicada’s dismal seventeen year internment as nymphs underground sucking on the xylem fluid of plants. During the past several weeks, millions of nymphs vacated the earth through their exit tunnels and dashed to vertical structures to shed their nymphal exoskeletons and emerge as adults. Within hours of this remarkable transformation, the adult’s appearance transforms from pale white to jet black as its exoskeleton hardens. Males and females quickly climb to the treetop to begin their courtship ritual. Male cicadas require from five to eighteen days before they begin calling and enter the mating game. To make the sounds necessary to woo his mate, male cicadas evolved unique structures called tymbals. These paired organs are located on the sides of their bodies just beneath the wings. Muscular contractions vibrate the membranous tymbals much like a drumhead to produce sound - and the sound they produce can be prodigious! Recorded at 90 decibels or more, cicada singing is as loud as a lawn mower engine or jet aircraft.
By vibrating the tymbal, the male cicada produces squawk and courtship calls.
Chorusing of thousands of cicadas in the treetops produces other-worldly sounds.
Males produce a variety of calls for different purposes. If threatened by a predator such as a bird or a squirrel, a loud squawking noise is made in an attempt to startle the predator and make an escape. However, the principal function of the tymbal is to produce calls that assist in attracting a mate and winning her affection. Since some emergences of periodical cicadas can include as many as four different species, one type of call attracts both males and females of the same species to a common assembly place such as a large tree. When the guys and gals get eye to eye, the male will use three distinct and different courtship songs to try and convince the gal that she should be the mother of his nymphs. If the lady likes his advances, she will signal her approval by flicking her wings, often with an audible click. After coupling for an hour or more, the male cicada inserts a copulatory plug into his mate, thereby curtailing further inseminations by other suitors. In a deal that seems patently unfair, it is believed that the male cicada then moves on and mates with other females. In the next episode of Bug of the Week, we will explore another chapter in the life of what may be the most fascinating member of the insect world, the periodical cicada.
This week’s episode was inspired by the crew of “Cicadas and Invaders,” a special production of Discovery Science. The wonderful article by K. S. Williams and C. Simon “The ecology, behavior, and evolution of periodical cicadas” was used as a resource for this episode.
To view other recent episodes of Bug of the Week that explore Brood II, and other excellent websites dedicated to cicadas, please click on the following links: