Cicadas 101

As Brood II emerges, Professor John Lill discusses the insects and what to expect this season.

May 28, 2013

Cicadas

They’re back.

After 17 years maturing underground, Brood II cicadas have surfaced for a few short weeks. With their distinctive red eyes, unearthly mating calls—not to mention the plague-like quantities they emerge incicadas are not your average insect.

John Lillassociate professor of biology, talked to George Washington Today about the insects, whether they pose a risk to humans or plants, and the mystery of their 17-year cycle.

Q: What can we expect in terms of when they'll arrive, and which areas of the region they will impact?

A: They are already here! Large numbers have emerged in specific places south and west of D.C. (and farther north, too, I think). Southern Maryland, including Calvert and St. Mary’s counties, has them, and a good chunk of Virginia around Bull Run and west of there are reporting large emergences. They don’t really migrate, so where they were 17 years ago is a good predictor of where they are now.   

Q: If there aren’t cicadas in your area yet, are you in the clear?

A: Yes, the cicada emergence is happening now and will be waning toward the end of the month, I believe. If you have not seen any yet in your area, odds are you won't! Unless you are quite a bit north of here where things will be behind like New England.

Q: Are cicadas harmful to people or the environment? 

A: They are absolutely not harmful to people, but some people seem to have insect phobias and should avoid them. They do some minor damage to canopy trees when females oviposit (lay eggs) in the ends of small branches. But the trees survive it just fine typically.

Q: Are cicadas related to other insects? 

A: All living things are related. Cicadas are most closely related to leafhoppers, treehoppers and froghoppers, all of which are “sucking insects” that feed on plant phloem or xylem. 

Q: How long do cicadas live? What do they eat? 

A: They live for 17 years, feeding as nymphs underground on the roots of canopy trees (sucking fluids from the roots). Once the adults emerge, they just mate and die, only living a few weeks.

Q: What does the 17-year cycle entail, and why is it 17 years?  

A: The insects are slow growing and probably feeding on a relatively nutrient poor source of food, so require a long period of development. No one knows why 17 years, although scientists have speculated about the prime number periodicity of cicadas (13 and 17 year varieties) as being an adaptation to avoid being “tracked” by important predators.

Q: What’s up with cicadas’ red eyes?

A: I don't know if anyone knows why they have red eyes! They sure are striking though. Many bright colors are used in animals for mate attraction as sexually selected traits, but in cicadas the “mating call” of the males (tymbal organs on the abdomen that make the loud clicking sound) probably reigns supreme as the most important aphrodisiac. 

Q: Is there a way to control or eliminate cicadas? 

A: Not really—just enjoy them while they are here! You can just move them outside if they get in your house or car. They don't harm people and are easily handled by grasping their thorax behind their head. They might call (if they’re male), which causes them to vibrate, but they won't hurt you in any way.