The daily buzz: Bellarmine Biology professor tells why we should be 'wowed' by Brood X cicadas

College of Arts and Sciences

Unless you’ve been living indoors with cotton balls in your ears, you’re well-aware of the emergence of Brood X, the 17-year periodical cicadas. Some of us may have even grown weary of them by now, as their numbers surge by the millions and their eerie mating songs reach deafening decibels.  

And yet, there’s much to be appreciated in this natural phenomenon we’re all experiencing. Bellarmine’s Dr. Anthony Lentz, professor emeritus of Biology, is here to help us understand how special and interesting these creatures truly are.

Q: As someone with expertise in entomology, what should the rest of us know or appreciate about these cicadas?

In broad terms, curiosity makes us smarter. Learning about or experiencing something new or unfamiliar enlarges our perspective beyond ourselves. This is an excellent opportunity for a person to challenge their preconceptions about insects by looking for and handling cicadas - they're easy to find right now, they don't bite, are slow to move and don't carry diseases. Their pointy feet will not hurt a person any more than butterfly's feet. I find insects fascinating because they are miniature versions of the animal world with all of the requisite parts yet are capable of profound changes in their body - metamorphosis - within a short time. For example, cicadas transition from being larvae with limbs adapted for digging into adults capable of flying in a matter of hours. Wow!  And, the suddenly large population of cicadas does not harm the environment.

Q: Speaking of the environment, what role do cicadas play in our local ecosystem? Do certain animals eat them? Do they serve some other function?

Cicadas enhance their ecosystems as they are excellent and plentiful sources of food to many animals – birds, squirrels, turtles, cats, dogs even fish. For example, the wild turkey population can increase significantly in the year following a large cicada hatch. Also, much like earthworms, they aerate the soil as they move around, promoting the growth of tree roots and trees.

Q: Is Bellarmine’s campus a good spot for cicadas?

The food source for larval cicadas is the root sap from almost any species of tree. They use their piercing-sucking mouthparts to penetrate the outer root layer and siphon the nutrient rich fluid. Bellarmine may harbor some isolated populations where the ground and trees haven't been disturbed since 2004, the last emergence of Brood X. That said, campus underwent significant construction during that period so anyone who is interested should look in the "natural" areas with large trees and underbrush. Cicadas have already appeared in some of the established neighborhoods surrounding Bellarmine so a walk near campus might be fruitful in the late morning or afternoon.

Q: I’ve seen in the media that cicadas are under attack by a nasty, disabling fungus that causes their abdomens to fall off. Has that fungus been detected in our cicada populations locally?

Sorry, I don't know. However, I've observed three different populations in the area and haven't seen any diseased cicadas.

Q: Curiously, I’ve heard folks from different parts of town who say they don’t have any cicadas yet, while others have seen countless numbers in their yards and neighborhoods. What accounts for this difference?

Cicadas appear in pockets for various reasons: they have different emergence days within a brood; a micro-environment that was hospitable to larvae may have become less so over the 17-year life cycle; when cicadas emerge, they don't fly very far from where they hatched 17 years earlier; and who knows?

General Brood X Information by Dr. Lentz

Cicadas are insects that resemble large, very robust house flies – they’re about an inch and a half long with stout bodies.

We commonly see annual or dog day cicadas around Kentuckiana every year, but … the cicadas that are emerging this spring are called periodical cicadas. This particular group, called Brood X, is special because the population is very large and it comes out of the ground just every 17 years to complete its life cycle.

People can identify periodical cicadas by three characteristics: their black bodies, bulging reddish-brown eyes, and clear wings with orange veins.

Life Cycle

They are the longest-lived insects known; most insects live short lives, from a few days or weeks to maybe a year. Cicadas break the mold on lifespan.

Tiny cicada nymphs hatch from eggs laid in a tree, drop to the ground and burrow in the dirt.  They stay underground for 17 years, actively feeding on the sap from tree roots, growing gradually, and burrowing as deep as 2 feet but typically not more than 5 feet away from their starting point – there’s no reason for a cicada to leave a continuous all-you-can-eat buffet.

After 17 years when the ground temperature becomes warm enough in spring, they dig their way to the surface and climb up the nearest vertical object – a tree, or post, a weed, an exterior wall. If people see their lawn dotted with small holes this spring, about the size of your little finger, cicadas are emerging.

They crawl out of their skin one more time (molt), inflate their wings and rest for a few hours until their new skin – their exoskeleton – hardens.

Periodical cicadas emerge from the ground in large numbers, typically late in the day. There can be more than a million adults per acre.

They’ll feed for a few days as adults then fly or crawl into trees and the males start singing to attract females. This sound is often the first thing that humans become aware of because cicadas are loud, even just one. And a mass of males is louder than a mower. People standing near them wouldn’t be able to talk to each other without shouting.

A female that is interested will flick her wings, creating a sound and attracting one or more males. After mating, she’ll lay up to 600 eggs on small twigs and, soon after, the adults die.  When the eggs hatch in about 6 weeks, the life cycle starts over. 

Other facts

Why 17 years? Environmental cues that signal cicadas to emerge are not well understood but may relate to cycles of tree sap availability, insect hormonal cycles and so on.

Males produce sound by vibrating membranes (tymbals) on their abdomens.  Females don’t sing.

Cicadas may land on people mowing their lawn because of the similar, loud sound. 

You can click your fingers if there’s a calling male nearby and it will come toward you because it thinks a female is flicking its wings.

Brood X is made up of three different species in the genus Magicicada.

Cicada Safari is a free crowdsourced mapping app for those interested in citizen science.


Tags: Biology

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