Steve Lekwa: Hear that? Brood X makes noise upon emergence
We recently returned from a long road trip to visit our son’s family in New Jersey. Part of the daily routine while there was taking our recently turned 2-year-old granddaughter for a walk.
Her awareness of her surroundings never ceases to amaze me. She called our attention to the moon being visible in the daytime sky. She loves spotting a rabbit or robin. At one point some blue jays flew into the top of a dying ash (emerald ash borers are very active there). She pointed at them and clearly said blue jay. I was astounded and quite proud.
She always notes if there’s a distant train. One late morning as we walked, she said “hear that.” Sure enough, I could hear the throbbing hum of cicadas. They were experiencing the first days of a 17-year cicada eruption.
Cicadas are one of our larger insects and are certainly among the loudest as males vibrate their tymbals, membranous little drumheads on each side of their abdomens. The sound is amplified as it resonates in their mostly hollow abdomen. An outbreak of periodic cicadas can lead to millions of males all sounding off at the same time over a several-week period.
Cicada densities can be as high as 1.5 million per acre. The combined sound of so many male cicadas looking for love is unlike anything else in nature (up to 90 decibels and more). They continue to sound off until they mate, and then they die.
Each female goes on to lay up to 600 eggs in the bark of living twigs on a wide variety of trees and bushes using a sharp “ovipositor” on the end of her abdomen to make a small slit. The eggs hatch into larvae that feed briefly on sap in the slit that their mother made but then drop to the ground and burrow in. They use their piercing mouthparts to feed on plant juices. They may attach to shallow grass roots at first, but they end up feeding on slightly deeper roots of trees and shrubs for the next 17 years. Established trees and shrubs tend to survive the attack by egg-laying females quite well, but young tender ones can be badly damaged or even killed.
There are several species of periodic cicadas that emerge in early summer every 13 to 17 years. The ones our granddaughter called our attention to are part of Brood X. Other broods occur in other years and in different parts of the country. Each different brood is given a Roman numeral. Iowa has periodic cicadas from broods III, IV and XIII. There are also annual cicadas, those buzzy bugs of dog-day afternoons in late July and August, but even those take two years to emerge as breeding adults. The annuals tend to be green and black or gray, while the periodic varieties are much more colorful with red, orange and black.
Any time nature produces a bumper crop of potential food, there will be a variety of creatures ready to gorge on that opportunity for extra protein. Hawks may join mice (their normal food) in gobbling up cicadas. Turkeys will get fat on them. Fish and turtles readily gulp down any that fall into lakes and streams. Songbirds, skunks, opossums and many more animals will fill up on them. Even people sometimes fry up protein-filled cicadas. Despite all the potential predators, periodic cicadas overwhelm the opposition with their numbers and always produce enough eggs to ensure another generation.
I have never heard 17-year cicadas in Story County but remember a very noisy week at Scout Camp Mitigwa south of Boone back in 1996 or ’97. They made so much noise that it was even hard to talk. Story County was dominated by prairie and wetlands before it was settled. Cicadas are entirely woodland creatures, and it’s possible that our more limited woodlands prevented populations of longer-term periodic cicadas from developing.
We’ll have to be satisfied with our annual dog-day cicadas. But if you want to hear one of nature’s most amazing sounds, just head east. Brood X will be there to greet you somewhere in Illinois or Indiana well into June.