Courtesy Bruce Marlin (via Wikipedia Creative Commons)Summer is heading our way and soon the familiar buzzing of cicadas will fill the air. But for some, particularly in the southern and eastern United States, the buzz will become a loud symphony of sound. That's because, this year, the Great Southern Brood will (actually already has in some places) reappear and millions of the insects will soon be crawling out of the ground to overwhelm us with their vast numbers and cacaphonic chorus.
Relax. Last weekend's rapture was a bust (or was it?), and there’s nothing to worry about in the biblical sense. It’s merely the latest appearance of Magicicada neotredecim and M. tredecim, two closely related species of cicada that show up every 13 years in the United States to fill the treetops with their buzzing song.
The most common genus of cicadas in the US is Tibicen and unlike Magicicada, cicadas in the genus Tibicen appear annually, not periodically. After a 2-3 year stint as nymphs, Tibecen cicadas emerge into their adult stage. The full-grown insect measures about 1-2 inches in length with long translucent wings and distinctive green, brown, and black markings on the middle of its body. Generations overlap so they show up every year and can be heard in many areas, including Minnesota, during the hot and steamy Dog Days of summer buzzing to high heaven. It’s that shrill, grating noise that builds in the air and sounds like someone is cutting up cement blocks with a chainsaw. As deafening as it can be, I like the sound, in much the same way I like the smell of rotting leaves in the fall, it triggers memories.
But I’m not sure how I’d feel about Tibicen's cyclical cousins - those belonging to the Magicada genus - that show up all at once in mass periodical emergences and put on huge choruses of buzzing. There are seven species that do this in the US, three in 13-year cycles, and four in 17-year cycles. Periodical cicadas are categorized into broods numbered in Roman numerals from I to XXX. The thirteen-year cycles occupy XVIII–XXX; seventeen-year cycles number I–XVII. Only about 15 broods are still recognized. There are still only seven cyclical species but some species emerge happen at different times in different regions, hence the number of broods. This year it will be a 13-year cycle called Brood XIX , and it is the largest of the 13-year cycles in terms of geography.
The numbers involved in a periodical swarm are huge but, as Vanderbilt biologist Patrick Abbot explains, the vast numbers increase the possibility of available mates and serve as a way to overwhelm the cicadas many predators, which include birds, snakes, turtles, spiders and wasps, and even fungi. It’s interesting that the periodical emergences have evolved into separate prime number cycles. The reason is probably to reduce competition between broods.
“Say you have two populations, one which emerges every five years and one which emerges every 10 years. Then they would emerge simultaneously every 10 years," Abbot said. "Whereas the period between simultaneous emergences between populations with 13- and 17-year cycles is 221 years."
Occasionally, two cyclical broods have been known to emerge simultaneously but usually the overlap is minimal. For example two 13-year broods rising at the same time but in adjacent regions.
During a brood’s synchronized emergence the number of individuals can be daunting. Some emergences have been estimated to contain something like 1.5 million cicadas per acre of land. That amounts to 800 tons (!) of biomass busily buzzing within a square mile of forest. Think of that!
But despite the huge numbers involved in a cyclical emergence, cicadas are pretty harmless, and don’t voraciously eat up crops like locusts do, nor do they sting or bite. The most damage done is by females when they make “v”-shaped slits in the bark of a twig to lay their eggs (I suppose this could feel like a sting if she mistakes your arm for a tree branch). But, come on, even this is nothing compared to a plague of locusts wiping out the summer corn crop.
The word cicada is Latin and means “buzzer” Very apropos, don’t you think? The males of the species spend a lot of time trying to get the attention of female cicadas by vibrating a membrane on their exoskeleton called tymbals. Each time the muscles contract or relax the tymbals they produce a click. Portions of the exoskeleton such as the abdomen or thorax help amplify the sound. The rapid vibration causes a shrill and (possibly annoying) buzzing, and each of the world’s estimated 2500-3000 species has its own distinct sound. The females, by comparison, make a rather boring click with their wings to attract males (I suppose the male cicadas don’t think it boring). You can replicate the female clicking by snapping your fingers in rapid succession a couple times.
When periodical cicada eggs hatch the nymphs drop down and burrow deep into the ground where they spend most of their lives sustaining themselves for several years ingesting fluids from tree roots and developing through five juvenile stages. Scientists suspect soil temperature triggers the emergence. When it reaches 64 degrees F., the nymphs head for the surface. It seems the likely catalyst since emergences in warmer, southern regions take place sooner than those farther north. Whatever the case, when they do emerge, the nymphs crawl up and attach themselves to nearby vegetation where they eventually molt out of their skins. They don’t begin adult activities until after their exoskeletons harden. So for the first 4 to 8 days after molting, they pass through a stage called teneral (meaning soft and tender) before the exoskeleton is complete. The adult stage of a cicada lasts anywhere from a couple weeks to a few months. Very short in comparison to their other life stages.
People eat cicadas in several areas of the world. And the females are meatier and more desired. I suppose the insect is a good source of protein but – there’s no way I’m ever doing that - I’d never eat one. Maybe I shouldn’t say “never”. Some Native American tribes supposedly survived times of famine by eating cicadas.
If you live in or are visiting an area that is or will soon be overrun by an invasion of the Great Southern Brood, rather than cowering in a corner and wailing and gnashing your teeth, head outside, go for a walk, and take in a symphony of cicada songs. While you’re out there enjoying the summer day, you can get even more involved by trying some of these neat cicada experiments. It will take your mind off the fact that you’re surrounded by 800 tons of buzzing biomass.
SOURCES and LINKS
A. When I got this question I thought of “cow hooves” because that is what I was always told, and thought here’s an opportunity to resolve that marshmallows are not made of cow hooves. It turns out, that while it’s not just hooves, hooves are a part of one ingredient of marshmallows: gelatin. According to KraftFoods.com (makers of Jet Puffed Marshmallows), marshmallows contain: corn syrup, sugar, dextrose, food starch - modified (corn), water, gelatin, tetrasodium pyrophosphate artificial and natural flavor, and artificial color (blue 1). There are links to some of the less familiar stuff, but gelatin is the most interesting ingredient as far as I am concerned. Gelatin is produced through the prolonged boiling of animal skin, connective tissue, hooves or bones. But marshmallows are not the only place where you’ll find gelatin – jelly, gummy candies, Jell-o, ice cream, margarine, cream cheese, and many other foods also contain gelatin. So, if eating hooves weirds you out, you can relax, you’ve probably eaten several already and not even known it.
Q: What do cicadas eat?
A: Sap from plants. The cicada's mouth parts are covered by a long thin sheath called a labium. The labium contains four needle-like stylets which are used to pierce the plant and then act as straws that the cicada used to suck the sap from the plant. If you are into cicadas and want to learn more, Cicada Mania is the place for you!
Q: How come there are no Native American artifacts in the Science Museum of Minnesota?
A: There are lots, actually. Like most museums, we display only 1-3% of our permanent collections, which number 1.75 million objects. Our anthropology collections span the globe, but our one of our strengths is in Native American material culture from the Upper Midwest. Currently in the museum, you can see a small exhibit detailing the Prairie Island Dakota community with a bison robe, star quilt and contemporary artwork by Francis Yellow and another on Native American archaeology of the area on level 5 in the Mississippi River Gallery. In addition, the museum is working on an Ethnobotany project with Paul Red Elk (Lakota) in the Big Back Yard where we are germinating indigenously cultivated seeds in a three sisters garden, some which are over 900 years old. The Science Museum has been involved in archaeological field investigations since the 1950s. The majority of these collections have been from sites in Minnesota and include 100,000 documented specimens from over 200 recorded prehistoric archaeological sites. Currently, SMM’s archaeology research initiative focuses on Red Wing Archaeology.