By RICK BORCHELT
Credit: Courtesy of Blake Layton/Mississippi State University Extension Service
Cicadas were all over the media this spring: Every newscast ran a story on the mass emergence of billions of periodical cicadas in the Midwest, recounting the cacophony of the double-brood overlap of 13- and 17-year periodical cicadas.
Although I did travel to the Midwest to see and hear the cacophony, all you need to do to observe cicadas in our area is walk any shaded street in the afternoon during the dog days of August.
Cicadas come in two flavors: annual and periodical. Periodical cicadas — red and black with scarlet eyes — don’t appear every year, but rather on a regular schedule with a decade or more between emergences. And when they do appear, they show up in deafening swarms of millions or billions; those swarms no doubt give rise to their often-used but erroneous alternate name of locusts (that name technically refers only to certain kinds of migratory grasshoppers).
Photo credit: Courtesy of Rutgers University Extension Service
Annual cicadas, by contrast, are with us every summer and represent the greatest diversity of cicada species in Maryland (and worldwide). In the suburbs around D.C., we can easily tick off 10 or more kinds of these brownish or greenish cicadas with light eyes on a good day in August.
Few of us see adult cicadas, though. Our species live high in trees, having spent a year or more underground sucking sap from shrub and tree roots. What we see more often are the dried brown husks left behind when immature cicadas (called nymphs) dig out of their underground nurseries and find a local tree (or brick wall, even) to climb before they rip their way out of their nymphal skin and emerge butterfly-like as diaphanous, green-winged creatures. After an hour or so their color darkens, and their wings expand and harden; the adults then fly up into the trees to sing (if they are male) and mate, leaving behind the cast-off shell. You can see a cool time-lapse video of the process at tinyurl.com/5dvetsp9.
While we did not have the astonishing periodical cicada emergence in the Midwest, here in our Streetcar Suburbs, any decent patch of trees will have cicadas singing this month. They might sound like salt shakers rising and falling in volume (that would be Linne’s cicada, Neotibicen linnei), or like someone rasping a file against a piece of metal (Robinson’s cicada, Neotibien robinsoniana), or like the pulsating of a police siren (scissor-grinder cicada, Neotibicen pruinosus). You can listen to all these, along with other likely cicada singer suspects, at the Songs of Insects website, which also includes crickets, katydids and other six-legged songsters.
Our most common annual cicada is the swamp cicada (Neotibicen tibicen), the very name of which reminds us that much of our area used to be wet forest and swamp. All cicadas sing louder and more energetically as the temperature rises; their song is a sure sign the dog days of summer have well and truly arrived.
Both nymph and adult cicadas find a place on the menu for songbirds, squirrels, chipmunks, snakes and even a large wasp, the Eastern cicada killer (Sphecius speciosus), which specializes in hunting cicadas.
Photo credit: Courtesy of Judy Gallagher
Male cicadas are especially prone to predation because they sing, and their song attracts predators and parasites alike. Only the males have a sound-producing organ, called a tymbal, on the abdomen, just behind the wings. Females lack tymbals and so can’t produce the high-decibel whines and buzzes of male cicadas, but both sexes have sophisticated acoustic sensors, tympani, to pick up the sounds of other cicadas.
While they don’t sing, females produce a variety of clicks and other sounds to alert males that they are receptive to mating. Males and females engage in a complicated auditory Marco-Polo courtship in the tree canopy and, if all goes according to plan, the male finds the female and they mate. The female uses a saw-like appendage at the tip of her abdomen (often sheathed, so it isn’t always apparent) to make slits in thin branchlets high in the trees into which she deposits her eggs.
After a few weeks, the rice-grain-sized nymphs hatch and fall to the ground — at least that’s the hope. If they land on a sidewalk or road, or in a spider web, or in a bird bath, it’s game over. But if they land on moist soil, they dig down until they hit a tree root, insert their straw-like mouthparts into it, and begin to drink sap.
We call this group annual cicadas because we see the adults every summer. In fact, though, their underground stage could last two to five years, depending on the species and the weather conditions. Unlike periodical cicadas, though, their emergence is not synchronized as a massive brood.
Then one summer, the nymph obeys some environmental command and begins its crawl upward. It will wait just below the surface, sometimes for a week or more, until a rain softens the soil. Then it fully emerges and begins its long slog up some vertical surface so it can then complete its transformation into a winged adult high in the treetops, where, if it’s a male, he provides our soundtrack for the heat of summer.
Have questions for Rick about the world of nature in and around the Maryland suburbs, or suggestions for future columns? Drop him a note at rborchelt@gmail.com.
