Periodical Cicadas (Magicicada spp.) take either 17 or 13 years to complete their development and emerge from the soil en masse as different "broods" in the spring. The only periodical cicada brood that's forecast to emerge this year is Brood VI. In fact, some members of this brood are already showing up within their historical geographical range of western parts of the Carolinas and a small area in northeast Georgia.
However, noted cicada expert, Gene Kritsky (Mount St. Joseph University, Cincinnati) is predicting that we will see an "early emergence" of some members of Brood X this spring even though adults of this brood are not expected to emerge full-force until 2021. Indeed, Gene is already getting reports of the emergence of some of these early-birds. This is one of the largest broods with a geographical range that includes parts or all of DE, GA, IL, IN, KY, MD, MI, NC, NJ, NY, OH, PA, TN, VA, WV, Washington DC.
We Need Your Help!
Neither Gene nor anyone else is predicting that this early-bird emergence will be anything like the Brood X mob that will appear in 2021. Only a very small percentage of the brood will appear this spring and significant twig dieback symptoms are not expected to occur. This means we need your help with documenting this unusual event.
If you see periodical cicadas, you can easily report your observation in two ways:
- You can e-mail a picture or pictures and the location where the images were taken to [cut-and-paste this e-mail address]: firstname.lastname@example.org
- You can fill out an online form maintained on the national "Cicada Mania" website by clicking on this hot link: Periodical Cicada Online Report Form
Periodical Background Information
Cicadas (family Cicadidae) are sucking insects and resemble huge aphids (they related). All cicadas develop through their immature stages (nymphs) deep within the soil where they use their piercing-sucking mouthparts to tap into tree roots. However, this feeding activity has never been shown to cause significant harm to overall tree health.
So-called Annual dog-day cicadas (Tibicen spp.) appear sporadically throughout the "dog days" of summer usually beginning sometime in July. Although it takes 2-3 years for dog-day cicadas to complete their development, some adults emerge every year due to overlapping generations.
The name "periodical" applies to cicadas that belong to the genus Magicicada spp. These cicadas require 13 or 17 years to complete their development. Adults emerge en masse in the spring, usually beginning sometime in May and ending in June. Adults climb the trees beneath which they developed or fly to new trees where males serenade females with cacophonous songs only appreciated by another cicada.
Mated females use their sharp ovipositors (ovi = egg, positor = deposit) to create slits in tree stems into which they insert eggs much like inserting letters into an envelope. Their damage to the vascular system commonly causes the stem beyond the slits to turn brown and die producing the symptom called "flagging" because it now looks like small flags tied to the ends of branches. In short, a full-blown periodical cicada brood emergence is not subtle.
Possible Explanations for an Early Appearance
If we could spin the clock back tens of thousands of years, we would most likely see a single huge emergence of periodical cicadas across the entire geographical range of this unusual eastern North American insect. It would be the stuff of dreams for entomologists … and nightmares for everyone else!
Groups of periodical cicadas gradually evolved over time to emerge during different calendar years producing the distinct broods that we see today. However, there is no reason to believe the environmental inducements that influenced the divergence of periodical cicadas into different broods have ceased to exist.
One explanation for seeing an "early emergence" of Brood X is that these are a diverging group that may eventually become a distinct brood. In 2000, Gene and others observed an emergence of a number of periodical cicadas 4 years before the main Brood X emergence that occurred as expected in 2004. Based on the number of adults that emerged, mated, and laid eggs, as well as the number of eggs that hatched (85%) om 2000, it would be reasonable to assume an early emergence this spring originated with these early-bird stranglers. Whether this splinter group maintains its cohesion to attain new brood status will be up to our descendants to decide.
However, Gene has noted that some of the cicadas that have been seen thus far this spring are not appearing where they were reported in 2000. This may be the result of some cicadas being missed and not reported in 2000, or it could be an indicator of something else much more significant. These stragglers may have experienced accelerated development based on warmer than normal temperatures associated with climate change. No one knows exactly how this new environmental incentive for evolutionary change will affect the biology of many insect species. However, it's certainly a new force to contend with; even if you're a cicada.