A week ago we provided a sneak preview of periodical cicadas as they prepared to make their debut in Columbia, MD. After receiving many reports last week of cicadas emerging in Northern Virginia, Rockville, College Park, Columbia, DC, Annapolis, and Bowie, I ventured out Sunday night and was greeted by hundreds of periodical cicadas scaling my neighbor’s massive pin oak tree in Columbia, MD. This same tree hosted hordes of Brood X cicadas back in the spring of 2004. Exactly which broods of periodical cicadas are emerging in the DMV this spring is somewhat a mystery. An early chronicler of periodical cicadas, Charles Lester Marlatt, noted an emergence of periodical cicadas called Brood VI in far flung regions of the United States. The greatest concentrations are known to occur in parts of South Carolina, North Carolina, Georgia, Wisconsin, and Ohio. However, Marlatt’s 1923 compilation of cicada sightings also included Delaware, Illinois, Indiana, Kentucky, Maryland, Michigan, New Jersey, New York, Oklahoma, Pennsylvania, Tennessee, Virginia, and West Virginia.
After almost seventeen years underground, it’s time to get up and out of the ground. A mad dash to the relative safety of a tree includes crossing a dangerous sidewalk before joining brood mates as they climb and prepare to molt.
In addition to Brood VI, cicada experts believe that some of the periodical cicadas we are witnessing belong to the Big Brood, Brood X, last seen in 2004 and slated for a return appearance in 2021. An early visit by Brood X comes courtesy of a curious developmental phenomenon of periodical cicadas known as acceleration. Accelerations occur when a portion of a cicada brood emerges years in advance of the billions of cicadas comprising the bulk of their ginormous synchronous brood. Cicadas that don’t emerge on schedule are called “stragglers” and if they emerge in advance of their brood mates they are called “precursors.” Historically, four year precursors in advance of a main brood have been observed in Washington DC, Chicago, Cincinnati, and other parts of the Midwest. These “shadow broods” may be self-perpetuating or they may be replenished by stragglers from other broods occurring in the same region.
The cloak of darkness signals the time to molt to adulthood for hundreds of cicada nymphs nurtured by this large pin oak tree. Molting is a treacherous time and a bump from a brood mate can send one tumbling to earth. Some will perish but many will again scale the tree, expand their wings, and prepare to find a mate.
For more than a decade, Brood VI and Brood X nymphs have been marking time underground since hatching from eggs in 2000 and 2004, respectively, perhaps by counting annual fluxes of plant hormones or amino acids in xylem sap, or by some yet unknown internal clock. Nymphs have been waiting for soil temperatures to hit the magic middle 60’s, signaling the world is warm enough for cicadas to molt, eat, fly, and mate. Chilly temperatures over the last couple of weeks may have held cicadas back a bit, but with temperatures expected to hit the 80’s and perhaps the 90’s later this week, the entire DMV region should be rocking with these teenagers by next weekend. So, grab a flashlight and look for a cicada jail break at night, and by day watch the antics of these amazing creatures as the big boy band cranks up in the treetops. And if you witness cicada events, please take time to participate in an important citizen science project detailed below.
CALL TO CITIZEN SCIENTISTS: we need your help! If you see periodical cicada nymphs, shed skins, adults on vegetation or on trees, please report your sightings to magicicada.org. Cicada experts are attempting to map the distribution of these magnificent and magical insects. Thank you for your help.
To learn more about all things cicada, please visit the following website: http://www.cicadamania.com/where.html
We thank Chris Simon for providing the inspiration for this episode. Two wonderful articles “Evolution of 13- and 17-year periodical cicadas (Homoptera: Cicadidae: Magicicada)” by C. Simon and “The ecology, behavior, and evolution of periodical cicadas” byK. S. Williams and C. Simon, and information contained at the “Periodical Cicada” web site (magicicada.org) by John Cooley, David Marshall, andChris Simon were used to prepare this episode.