IRA FLATOW: This is Science Friday. I’m Ira Flatow. We’re in Iowa this week. This spring, you may hear a familiar sound.

[CICADAS BUZZING]

Cicadas, yes, they can be pretty loud. And in fact, in parts of the Midwest and the American south, two broods of cicadas are emerging. Brood 19, the great Southern brood, and brood 13, the Northern Illinois brood. The dual emergence of these two particular broods is a rare event. The last time they appeared together was in 1803. Both broods can be seen in Illinois and Eastern Iowa. And joining me now to talk about these broods is Dr. Laura Isles, entomologist at Iowa State University in Ames, Iowa. Welcome to Science Friday.

LAURA ISLES: Thank you so much. It’s a pleasure to be here.

IRA FLATOW: It’s nice to have you. Oh my. This double brood emergence sounds pretty exciting. Are you excited by it?

LAURA ISLES: As an entomologist, I am definitely excited. I’m excited to have any brood. You know, living in one place. You don’t– they don’t happen all that often. And so I was lucky in 2014 when we had a brood right here in Central Iowa. But I’m definitely going to travel to Eastern Iowa and see at least the brood 13 emerging there. So very excited about it.

IRA FLATOW: Well, tell me why you would travel to see the brood. What is so special about what’s going on?

LAURA ISLES: Well, so these are the periodical cicadas. And so we’ve got the 13 year or 17 year broods. And so there’s just thousands of them, upon thousands, at the same time, and in the same location.

IRA FLATOW: Well, what do you see? Are they flying? Are they– what are they doing that’s so amazing?

LAURA ISLES: Yeah, so they’re kind of doing a lot of things. So, you know, the singing is what always, you know, catches people. So the males will gather together in a chorus and they’ll sing together. And the sound is kind of deafening. But I mean, to me, it’s kind of beautiful. Maybe because I get to travel and go see it, don’t have to put up with it all day long. But yeah. Cicadas, there’s a term, the cicada specialists use, they say they’re predator foolhardy, which essentially means they really don’t even try to run away. So you can really look at them, and you’ll be able to see females laying eggs. You’ll be able to see them just sitting on the undergrowth, hear them singing in the trees. So you really can go and just immerse yourself in cicadas, if that’s what something you would enjoy.

IRA FLATOW: Well, speaking of enjoying it, let me ask you about the singing. I never heard it described as singing, but it is, right? I mean, are they singing to communicate with each other? Or are they singing to keep predators away? I mean, because they’re pretty loud, right.

LAURA ISLES: Right, they’re very loud. And they’re singing to communicate. So it’s just the males that can sing, and they’re communicating with the females, come here. They have a pretty short life span, a few weeks as adults. And they’re really– their job is to mate and lay eggs. And so the males gather together so they can be even louder and attract females to the area for those mating opportunities. OK, I know we’re not supposed to anthropomorphize with insects, but think about them kind of underground around for 13 or 17 years. I don’t know. I kind think, it’s kind of cold. I don’t know if they even, like, see each other under there, or come across other cicadas. So they’re probably kind of alone. And then this is their chance to emerge and be in the sunlight and fly and, you know, meet other cicadas.

IRA FLATOW: Yeah, wow. And can you tell different broods apart by the songs they sing? I mean, could you hear one and say, oh, it’s that one, that’s where they are. And look, there’s another one.

LAURA ISLES: Yeah, so you can tell the different species of cicadas apart, and a brood is just a term for the cicadas that will emerge in a certain geographical area in a certain year, and each brood will have several species in it.

IRA FLATOW: Yeah so there is some evolutionary advantage then of this life cycle style.

LAURA ISLES: Yeah, so this very long life cycle style, the belief and probably likelihood is that it keeps any predators from, you know, getting that same life cycle. So it’s not unusual to have plants to only produce seeds every few years, or in this, you know, so it’s like they just escape from predators that way, because there’s really no predator that could go without, you know, feeding for 13 or 17 years. And then they just come out in such huge numbers that no predators could eat all of them. So they’re very vulnerable to birds and snakes and lots of other things. But there’s just so many of them that they can’t possibly eat all of them.

IRA FLATOW: Well, you kind of answered the question. If I was another– if I was a predator and I saw a gazillion of these cicadas coming out, I’d say it’s party time, right? I mean, what feeds on them?

LAURA ISLES: Yeah, so many species of birds do. You know, certainly raccoons. Basically, anything will eat them. They’re not like wasps. They can’t sting. They don’t contain any chemicals. I mean, they are really just– like they say, predator foolhardy. They don’t even, you know, fly away really. So they just don’t have a big, strong response when something’s coming to eat them. Because, again, they’re just– like it’s such huge numbers that that’s how they’ve evolved to do it. Is just to be present in such huge numbers.

IRA FLATOW: Yeah. So where do they lay their eggs? I mean, and can you see them actually doing it?

LAURA ISLES: Yeah, definitely. So it’s the female, and she has a structure called an ovipositor. Ova is just a name for egg. So she has this structure that she can kind of cut into the tree branch. So she’ll be on the underside of a twig usually, and she’ll just be poking this ovipositor into it. So she’ll make a little slice in the twig, lay about 20 eggs in there, and then she’ll just move a little bit further down the twig, make another slice, lay some eggs in it. And so you’ll see just like a little series of little, almost v-shaped slices in a twig where the female has laid eggs. So you can definitely watch this happening if you go into an area after cicadas have been there, you can see it. Sometimes you’ll get some twig dieback from the damage called flagging. So it’s definitely something pretty noticeable in areas where there’s been a brood emerge.

IRA FLATOW: So where do they get to the ground stage of this?

LAURA ISLES: So the eggs will be in that twig about 6 to 10 weeks, and then they hatch. And then this tiny little nymph just almost clear, whitish colored, tiny nymph hatches out of it and falls to the ground, and then burrows under the ground and seeks out a root to start feeding. And they’re not terribly picky at first. They’ll feed on pretty much any plant root that they run across. And then as they get, you know, larger, they seek out tree roots, and set up feeding sites and feed on those.

IRA FLATOW: Wow, you know, maybe it’s because the eclipse was so recent, but this special cicada event makes me think we might see some cicada tourism in Illinois, and possibly Eastern Iowa. Or is that a real thing? Oh, for sure. I’ve definitely been on lots of message boards where people are talking about planning trips. I know a lot of us here in Central Iowa, since we won’t have any, we’ll drive out to Eastern Iowa. I think this will, I mean, I was one who traveled eight hours for the eclipse, and it took, you know what, like 12 hours to get home with all the traffic. So.

IRA FLATOW: I know. Yeah, I’ve been there.

LAURA ISLES: Yep, yep, yep. And the eclipse is like a really kind of intense moment, you know. Two to four minutes and then everyone hits the road at the same time. Like, the nice thing about touristing for cicadas is, you can go there all day, you can go there for a few hours. Like there isn’t quite that like, you know, once you find a nice area, you’re not worried about cloud cover, and all the other things that went into eclipse chasing. Yeah, this is low stress.

IRA FLATOW: Good point. Now it is spring and people are tending their gardens. Should local gardeners adjust their plans while the cicadas are doing their thing?

LAURA ISLES: Yeah, and again, they tend to be patchy where they’re emerging. So, you know, if your neighborhood is a place where you’ve known in the past, you know, that, you know, 13 years ago or 17 years ago, they emerged here, then you very likely they’re going to emerge again this year. And our recommendation is this might not be the best spring to plant a new tree, because a little bit of that twig damage can be harder on new trees. You know, maybe a fall planting is just as good for trees.

And if you have, I spend my money on my landscape, so I have some Japanese maple looking trees that, you know, I spent, you know, $250 for. And I love them, and prune them delicately each spring. So that would be the tree that you’d, you know, just go online, buy like tool fabric, garden netting, row covers, you know, purchase some of that and cover them up for the few weeks to prevent that egg laying. But again, it would have to be something pretty high value and small. A large tree, well, first of all, you couldn’t cover it very well. And second of all, the tree’s just fine. That little bit of just minor damage.

IRA FLATOW: OK, that’s good advice. OK now, since you’ve whetted everybody’s appetite for going out to see the cicadas, I’m really, I’m excited. For people who want to see them, maybe do some cicada tourism, how can they best go about this without hurting the cicadas?

LAURA ISLES: So the key is to finding a place to go. And I’ve got an app called Cicada Safari right now. There’s, you know, websites, Cicada Mania is great. Like find out what parks in your area. You know, State Park, City Parks have had cicadas in the past. Many of them are kind of advertising it. And I know in Illinois, where those two broods were really overlapped, there’s, you know, some County Parks and things, planting kind of festivals and fun activities for kids around it. So just kind of pick your location. Here in Iowa. It’s really along, you know, river areas. Between Iowa City, Cedar Rapids is a very likely place. That’s probably where I’m going to head. So you pick your location. You know, they’re already emerging in the South. We expect them kind of late May.

IRA FLATOW: Well, I was going to ask? Is there an ideal time? Is there a peak date?

LAURA ISLES: Unfortunately, it’s the soil temperature being about 64 at 8 inches. But that’s hard information to get for your area. Yeah, the Southern US are just starting to emerge. The Missouri Southern probably early May, and we won’t be here up in the upper Midwest until, you know, May or June. But yeah, set those dates, and then, you know, just be kind of prepared to travel and plan to spend, you know, an afternoon or two here in Iowa. And I know this isn’t like everywhere. Here in Iowa. It tends to be pretty patchy even within a park. So, you know, talk to someone, you know, a Ranger or somebody about, you know, what path to hike on, and the best places to go see them.

IRA FLATOW: You know, I was going to ask you how you convince people that these are worth going to see, but I just have to listen to your enthusiasm. And I think you’ve convinced a lot of people not to be afraid of them. Go out and go see some cicadas.

LAURA ISLES: I hope so. The sound, and you can hear it from a distance. And as you just hear that sound and then walk into an area where the males are chorusing, it’s pretty cool. I encourage it.

IRA FLATOW: I’ve never heard the word chorusing applied to a cicada before, so thank you very much for that, Dr. Isles. Dr. Laura Isles, entomologist at Iowa State University in Ames. Thank you for joining us.

LAURA ISLES: Thank you so much.

IRA FLATOW: And we have a story on our website all about this special double brood emergence. Go to sciencefriday.com/cicadas. Notice I put the S on that sciencefriday.com/cicadas with an S.

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