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Answers to your questions about Brood X cicadas: How long can we expect them and how to track them?

Dr. Jerome Grant, a professor of entomology and plant pathology with the University of Tennessee Institute of Agriculture, shared answers to many Brood X questions.

KNOXVILLE, Tenn. — As Brood X cicadas get ready to make their once in every 17 years appearance, there is quite a buzz.

Whether you want to know what to expect or if these creepy crawlers could be a good snack, the University of Tennessee went to the experts for some insight.

Dr. Jerome Grant, a professor of entomology and plant pathology with the UT Institute of Agriculture, shared answers to many questions related to Brood X.

What is the scope of insects compared to humans?

Insects are fascinating creatures. Seventy-five percent of life on earth is insects. Insects outnumber us about 200-250 million insects per person. There's about 1 million different described species of insects, and scientists estimate there might be as many as 10-20 million more out there. Plus, if you look at it on a weight basis, for every pound of human, there's about 300 pounds of insects.

What is Brood X?

Brood X is a type of periodical cicada. Periodical cicadas are the cicadas that have a long life cycle. So they're every 13, or every 17 years. Brood X happens to be a 17-year cicada, which means the last time it was out of the ground was 2004. The next time it'll come out will be 2038. So this is a unique opportunity to observe one of the best biological phenomenons that occur in East Tennessee and other areas of the eastern US.

When will we see Brood X emerge?

You know, probably in the next couple of weeks, we'll start seeing emergence depending upon the temperatures at night and during the day. So if we have a lot of warm temperatures, there's a chance they might emerge earlier. If we have some colder temperatures, they might be delayed a little bit, but we're expecting the immatures to come out of the ground around Mother's Day. And when they come out of the ground, they'll make these little holes so you might see little round holes in your yard. That's where the cicadas are digging themselves out of the ground. Then they'll find a vertical surface, it might be the trunk of a tree, might be a fence post, it might be the side of your house or another structure. And these little brown objects that look like prehistoric creatures will crawl up. And that's where the adult will emerge from so they'll attach themselves and the adult emerges from that as it molts and it leaves behind the cast skin So you'll probably see a lot of these cast skins. They're harmless, they're not going to do anything, but that's just the remain to the cicada. So the cicada will sit there for a little bit while it hardens and becomes a fully developed adult. And then it'll go do what cicadas do, that's fine another mate and make a lot of sounds.

What has to occur before they emerge?

One of the most important things that has to occur before they emerge out of the soul is the soul has to reach a certain temperature. So when it reaches about 64-67 degrees at four inches beneath the soil surface is when the adults will start coming out.

Where will BroodX emerge?

Well, Brood X is one of our largest broods of cicada, if not the largest brood of cicada we have occurring. And this one will be found across 15 states, from the Atlantic to the Midwest, and from Michigan down to Georgia. And fortunately for us this year, Tennessee is included in that distribution. So we'll be one of the 15 states that are experiencing Brood X this year. Not everyone in Tennessee will experience it, mainly in East Tennessee, but there are some counties in Middle and West Tennessee that will also have some Brood X.

Will everyone in those areas get to enjoy the cicadas?

Just because your state is experiencing Brood X does not mean that you'll necessarily experience it in your area.

What kind of cicadas are there in Tennessee?

We have two different kinds of cicadas in Tennessee. So every year, you'll hear cicadas, and those are Dog Day cicadas, is what we call them. They come out later in the summer but we'll have those every year. They're larger, they're green, the bodies are green, and you'll hear them every year. So they're not to be confused with periodical cicadas, which come out on these 13 or 17-year cycles. And they're much smaller, and they have an orange coloration to them, which is really pretty interesting since, you know, we're Volunteer fans.

How can people enjoy this natural phenomenon?

I encourage people to get out and try to observe as much as they can of this occurrence because it's not going to come again for 17 years. So it's a wonderful family outing-type atmosphere.

How long can we expect them?

They'll emerge for about two weeks. So they live maybe four to five weeks, so you can expect them from mid-May to about the end of June. But by the end of June, they'll be really tapering off. So you're looking at the first part of June, maybe the first two weeks of June as being the peak noise-producing time.

What is a cicada?

Cicadas are often confused with locusts, which is a type of grasshopper, and that's not what they are. They're actually very closely related to scaled insects and aphids, if you're familiar with those are, just the very large version of it, but it is an insect. It has a piercing-sucking mouthpart, which means that it has a needle-like mouthpart that it inserts into the plant and it withdraws liquid, and that's how it gets its nourishment. It does not have chewing mouthparts. So it can't chew plants. It can't bite us. It can't do anything like that. But when it's beneath the ground, it feeds on the roots of trees. When it's above ground, it feeds on the sap of the trees.

What are the benefits of cicadas?

Cicadas are actually very beneficial to us. They're the natural part of our ecosystem. But remember, they're underground, these periodical cicadas, for 17 years. So they're aerating the soil. They're providing tremendous benefit there. Once they emerge, they're a food source for a tremendous number of animals, mainly for birds. Plus, once they start dying, they provide a lot of nitrogen and other nutrients back to the soil for recycling and use by other organisms, and they are a natural tree pruner.

Does the sound cicadas make mean anything?

To cicadas ears, if you will, it's a mating call. So only the male cicada produces the sound, and the male cicada produces the sound to attract females for mating purposes so they can continue the population. The sounds we hear might be annoying to some of us, they may be pleasant for some of us, but for the insect, it's the only way it can find a mate and reproduce and continue the population. 

How loud is the sound?

Well, cicadas actually produced a very loud sound, as most of us know when it runs anywhere from 85 to 100 decibels. And that's pretty much equivalent to a low flying airplane or a lawnmower, in some cases, maybe a jet engine.

What is the life cycle of a periodical cicada?

The life cycle of periodical cicada is fascinating. Whether you're an entomologist or not, it's just fascinating because when you think about it, they've been underground 17 years, they come out, they mate, they reproduce, the female lays her eggs in the slit, and then those eggs will take about two weeks to develop into nymphs. And then those little nymphs, no matter where they are in the tree, they emerge and drop down to the ground, and then they go into the ground and they're not seen again for 17 years if it's a 17-year periodical cicada.

Is there anything else in the Eastern part of the U.S. with this type of life cycle?

There's nothing else that occurs in the eastern US that I'm aware of that has this type of life cycle except for periodical cicadas, and we do have 13-year periodical cicadas and 17-year periodical cicadas. So we have different year cycles and different broods. So in 2024, we're going to have a 13-year brood emerge, and it'll mainly be in Middle Tennessee, and in 2025, we're going to have another 17-year cicada emerge here in East Tennessee.

Are cicadas harmful to people or pets?

Cicadas are not harmful to people or pets. They do not bite. They do not sting. They're not poisonous or toxic to us. They do make a sound, and if pets overeat them, they may get upset stomachs.

Can cicadas do any harm to plants or trees?

In normal plants in your landscape, azaleas, Rhododendron, cicadas are harmless. Remember, they don't have chewing mouthparts. They do have piercing-sucking mouthparts, but they don't feed on ornamental plants, they feed on trees. But if you do have trees in your landscape, especially young trees, cicadas can damage those trees, not by feeding, but by egg-laying. The females have a very special egg-laying structure, and it resembles a knife. So the female will cut a slit into the twig and she lays her eggs in that slit and then beyond that slit, the leaves and foliage will turn brown, and then it dies. So you can sit get natural pruning in the tree, and you wouldn't want that on your younger trees.

What can you do with the shells left behind?

Well, the brown cast skins or shales that are left behind, they cause no issues whatsoever. They will eventually degrade and go back to nutrients that can be used by other organisms. If you'd like to, you can go around and pick them off if they're unsightly to you and throw them in a compost pile or something like that. Or you can use them as an educational tool for your kids or for your neighbors, you know, have fun with them.

Are cicadas edible?

Yes, cicadas are like a lot of other insects. They are edible, and there are several cookbooks available if you're interested in how to cook cicadas. It's a very good dish. People say it tastes like cooked asparagus. Some people say it tastes like shrimp. I think they taste more like almonds because they have a nutty flavor. But they are high in protein. They're very low in fat and low in cholesterol. They're gluten-free, so they have a lot of good qualities about them.

Who shouldn't eat insects?

If you are allergic to shellfish, please do not eat insects, do not eat cicadas because they're very closely related to shrimp, to lobsters, to crabs, but if you enjoy those foods, then you should enjoy insects as well.

Is there anything to keep in mind when collecting cicadas for consumption?

Yes, if you're interested in edible cicadas and in trying to collect some to cook, please be careful of where you collect these from because in landscapes there's a lot of pesticides that are used. You don't want to collect cicadas from areas like that.

Do people really eat insects?

Entomophagy, which is the consumption of insects, it's a very common occurrence throughout the world, but it's not in the US or Canada because we have a phobia or a fear of eating insects. But in other countries, it's a very natural part of their diet. Two and a half billion people consume insects on a regular basis, and there's even more than that, that consume it sometimes throughout the year, either as a delicacy or these things just emerge at one time and they can eat them then.

Why do many people not like the idea of eating insects?

We just have a phobia, we have a fear about eating insects, but if you think about it, when people first started eating lobsters, lobsters were disgusting creatures. People didn't like lobsters, and now lobsters are a delicacy and people love them. So you know insects can be worked into that same category.

Where can people learn more and track cicadas?

If you're interested, there's an app that you can download, either on your iPhone or your Android phone, and it's called Cicada Safari. It's developed by a group of scientists led by Gene Kritsky, who is our leading expert in the United States on periodical cicadas. This Cicada Safari app allows us as individuals to track cicadas in our area. So it's a great opportunity for the general public to get involved in helping us track patterns, helping us find out where cicadas are occurring, and it can help us better understand periodical cicadas.