By Therese Ciesinski, GardenSMART
Images by Dr. Gene Kritsky, Mount St. Joseph University
Like those college kids on spring break in Miami, the Brood X periodical cicadas are hard-partying visitors with red eyes and a preference for deafening music. After 17 years in the ground, warming temperatures means they are showing up by the trillions over a swath of the Eastern United States, a weeks-long event that culminates in a new batch of babies and lots and lots of dead cicadas.
These are periodical cicadas, not the noisy ones that appear every year in late summer. Periodical cicadas (Magicicada) spend almost all of their life in the soil, feeding on tree roots and waiting for the signal to emerge, mate, and die. Different species of cicadas have different life cycles. Brood X are 17-year cicadas. There are also 13-year periodical cicadas.
Cicadas are in the order Hemiptera, and related to bedbugs, aphids, and stink bugs. Of all the broods, Brood X is the largest, covering parts of 15 states, from New York State to eastern Illinois to northern Georgia, where the cicadas are already emerging. In other years, broods are found from Massachusetts down through every southern state except Florida, and into the Midwest from Nebraska into Texas. (The broods are numbered with Roman numerals, so Brood X is Brood 10, not the letter X.)
Cicadas emerge at night once soil temperatures reach 64 degrees F, crawl onto nearby vegetation, and spend a few days molting into adults, darkening from white to black, and growing about an inch long. Then mating begins. Males call to the females, making an ear-splitting racket. After mating, the females fly into the trees to lay their eggs. A female makes a slice in the bark of a tree’s new growth with her ovipositor and deposits the eggs. Their job done, the adults then die.
After six to ten weeks the eggs hatch and the cicada nymphs feed on the sap inside the branch. This can cause some twigs and branches to die back, but in general this won’t kill a mature tree. They then drop off the tree into the soil, burrow down about eight inches, and start their 17-year wait.
There can be as many as 1.5 million cicadas in an acre. Why do they emerge all at once? The idea is safety in numbers: Show up all at the same time and predators can’t devour them all, not that they won’t try. What eats cicadas? Birds, mammals, fish, reptiles, dogs – who are said to love them – and a few adventurous people. The insects supposedly taste like canned asparagus. Adult cicadas don’t eat solid food once they emerge, though they do take in liquids. This means they excrete, so for a few buzzy weeks, wear a hat.
There’s an app for citizen scientists to track Brood X and help with scientific research. It’s called Cicada Safari (cicadasafari.org). It was created by entomologist Gene Kritsky and his team at Mount St. Joseph University in Cincinnati, Ohio.
Cicadas are harmless; they do not bite, sting, or carry disease. However, the developing nymphs occasionally cause enough damage to small or young trees to disfigure or kill them. If you have prized trees, wrap them in netting (watch for gaps) for the six or so weeks the insects are active. Make sure the holes are ½” or less. Bird netting is too big. Don’t net trees until cicadas emerge, and don’t use spun fabric or any fabric that will impede air circulation around the tree.
Don’t bother trying to protect your trees with pesticides. Whether organic or synthetic, it’s futile. You’ll kill some cicadas, but others will just take their place. There are just too many. Make peace with the fact that you’re outnumbered and take consolation: they won’t be around for long.
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