What’s that buzz in the backyard? No, it’s not Bugzilla, but the return of millions of periodical cicadas, one of the world’s longest-lived insects. Because all that racket often makes it hard to concentrate, this month’s Bay Buddies is designed to tickle your fancy and not your brain.
Safety in Numbers
This year’s emergence is Brood X, also known as the “Big Brood” because of its extensive range, (from New York and New Jersey west to Michigan down the Ohio Valley south to parts of Missouri and into Tennessee and Georgia) and its great abundance—in some wooded areas , up to 1.5 million per acre.
These high numbers are music to the ears of creatures who prey on cicadas, which is practically everything—from birds and bats and dogs and cats to spiders and snakes. The survival rate of songbird nestlings increases during a cicada emergence because their parents don’t have to search as hard for food. Likewise, the population of moles, which feed on the underground nymphs just before they emerge, also spikes these years.
Fortunately, the large numbers also ensure that there are enough adults leftover to mate and produce the next generation of snacks.
Name That Tune
There are seven species of periodical cicadas in North America: four species that emerge every 13 years (generally found in the South and Midwest) and three that emerge every 17 years and are usually found in the North, including Brood X. Each of the 17-year species has its own song. Even though more than one species may emerge at the same, careful listeners should be able to figure out which is which. Magicicada septemdecim sounds like “pharaoh,” and most commonly sings in the morning. If it’s mid to late afternoon and sounds like someone trying to start up a lawn mower, that’s M. cassini. Midday “lawn mowers running smoothly,” are M. septendecula.
Lucky7(teen) & 13, or A Prime Advantage
Because the numbers 13 and 17 are large prime numbers (only divisible by 1 and itself), the life cycles of periodical cicadas make it almost impossible for a predator or parasite species to base its survival solely on cicadas because the longer the prime-number cycle, the fewer opportunities for predator and prey life cycles to coincide.
To calculate the how many times a cicada emergence will coincide with a predator or parasite, multiply the life cycle of the cicada—17 (or 13)—by that of the parasite or predator. Therefore, a creature with a 2-year cycle will meet up with the 17-year periodical cicada once every 34 (26) years, because that is the least common multiple of the two numbers. A creature with a 3-year cycle will only coincide with the cicada every 51 (39) years, For a 4-year cycle it’s 68 (52) years; for a 5-year cycle it’s 85 (65) years!
On another note, these numbers also reduce the occasions when more than one cicada brood will emerge at a time to compete for food.
Don't Chew, Know That We Suck
Cicadas are members of the Order Homoptera, sap-sucking insects with beaklike mouth parts. Cicada nymphs suck sap from roots, while adult cicadas suck the sap from tree twigs. Homoptera means “similar wing,” and stems from their undivided, uniformly membranous wings.
Other Homoptera relatives include: leafhoppers, treehoppers, spittlebugs, whiteflies, aphids and mealybugs.
Cicadas are often called “locusts,” but the two insects are not kin. Locusts, which chew and eat vegetation, are related to grasshoppers.
The Boys In the Band
If you think the cicadas are loud, imagine what it would sound like if the whole population were singing, instead of only half of it. For the most part, what we hear is an all-male ensemble singing its heart out in an effort to attract females. The louder the lure, the more attractive the serenade, so solo acts in the cicada aren’t as big a hit with the ladies as a male chorus.
Love Is Blind, Not Deaf
Cicadas do not attack humans. It’s just that their clumsy flight skills often put them on a collision course with humans, who may appear to be just another landing pad. At other times, the sound of a running lawn mower or other garden machine may be so similar to the species’ mating call that the insect is just looking to make little music together.
If You Can't Beat 'em, Eat 'em
The Biology Home Page for the University of Cincinnati-Clermont College features recipes for Battered & Deep-Fried “Cicada Shrimp,” Cicada Stir-Fry and for dessert: 1902 Cicada Rhubarb Pie.