Nature Boost
April 2023 Episode
KRG
[Music playing.]
>> Hey there and welcome back to Nature Boost. I'm Jill Pritchard with the Missouri Department of Conservation. If you've lived in the central or eastern U.S. you know this sound.
[Cicada]
That famous cicada call has been the theme song for most of our summers. I remember marveling as a kid finding their shed skin on the ground or the trunk of a tree. 2024 brings the great cicada emergence with periodicals tunneling to the surface after spending years underground. The lifecycle of these insects is so fascinating and I wanted to learn more about them before they emerge in the coming weeks. I was really thrilled whenever I was able to sit down with MDC Forest Entomologist Robbie Doerhoff to learn more.
[Music playing.]
>> They live underground. Let's do it.
>> Yeah, what is a cicada?
>> Cicada is a general term for a pretty common group of insects that we see in Missouri. They are really neat because part of their life cycle is underground, and part of it is above ground. It is something that we see. They sing. They are really neat to see in the summertime.
>> Are cicadas the same as locusts?
>> Ooh, that is a good question. When I was growing up I always called them locusts, but no, they are not the same. Locust is a term we should reserve for grasshoppers. Some people in different parts of the world even katydids. But in general, locust is not the right term for cicada. Some people even call cicadas jar flies.
[2:00.]
In Latin, "cicada" means "tree cricket."
>> Okay, interesting. I am glad you said that. I have always heard people use "cicada" and "locust" interchangeably. But that is not the case.
>> Yes, no, that is not the case. Although that is something we commonly say that is not the proper scientific term.
>> So cicadas are huge in the news this year because we are going to have the periodical cicadas emerge, correct?
>> Yes, that's correct. Every year we see the annual cicadas which actually most of them have a 2-5 year life cycle. But these periodical cicadas we only see those every 13-17 years, depending on which brood.
>> The brood that we are seeing is the 13-year one?
>> Yes. It is brood 19. It is made up of four 13-year species.
>> When in the year do they start to emerge?
>> That is a great question. Insects' life cycles are dictated by temperature. For cicadas being underground, they are relying on soil temperature to tell them when it is time to come out. For periodical cicadas, it is known that when the soil is at 8 inches deep reaches 65 degrees Fahrenheit, that is about the time they will start to emerge. So for us above ground, that generally equates to when the iris bloom. If you know what iris are, then once they start to open up their blooms, expect you will be seeing periodical cicadas emerge soon.
>> Interesting, iris blooming can be a sign of when they will come out.
>> Yes, we call these phenological indicators. Plants are also dictated by temperature. So when they start blooming, different plants bloom at different times throughout the spring and that is all based on temperature. We know certain things in the insect world happen at certain times when plants are doing their thing, too. We can kind of correlate those because it all relates back to temperature.
[4:05.]
>> Tell us briefly about their life cycle. It is pretty interesting.
>> Yeah, it is interesting but it is also simple. Female cicadas lay eggs, and then those eggs hatch into nymphs. The nymphs are in the ground for whatever amount of time it is that is appropriate for that species. Then they come out of the ground. They usually crawl up onto something high like a tree or shrub. The back of their exoskeleton splits open as they molt, that original nymphal exoskeleton. They emerge as an adult and they pump their wings full of hemolymph to open them up. They dry, and then they go about their adult business of singing, mating, feeding a little bit, and then they die. The shortest part of their life cycle is the adult phase. After they mate and lay eggs, that is the end for them. The cycle starts over.
>> These cicadas are underground and alive the whole time?
>> Yes, exactly. The female cicada actually lays eggs into small-diameter twigs. Twigs about the size of your pinky finger. She will cut little slits in those twigs and lay eggs in there. Then those eggs will hatch into tiny little nymphs that feed a little bit off the xylem of that tree before dropping to the ground. They will burrow into the ground, fairly deeply. I have seen them 2-3 feet deep into the ground before. When they are real tiny they will find grass roots or other fine roots to attach to and feed the xylem material from those roots. Then as they get larger through the years, they will find larger roots, usually tree roots, to feed on.
It all starts as a teeny tiny egg and then nymphs that grow bigger and bigger over time. As many as 98% of those tiny nymphs will die in the first couple of years. What we see emerge 13 or 17 years later is estimated as maybe only 2% of what eggs were originally laid. Most die before they even reach 13 or 17 years in adulthood.
[6:21.]
>> Why do you think they die before they can reemerge again? Is there not enough food source for them down there?
>> There is a variety of reasons this could happen. Some probably become mole food or other soil burrowing animals and insect predators that will eat them. Some of it may be because of temperature or desiccation or drying out. Maybe we have a drought and it is just too dry in the upper layers of soil. Some of it could be from habitat loss or pesticide use in a lawn. If you are using insecticides in your lawn you might be inadvertently killing things like this that are really cool.
Habitat loss as we deforest places around cities to pave over or build houses the cicadas are not going to survive in those areas. They don't move long distances. They won't be able to find a new place. There are lots of reasons why in 13 or 17 years they may die.
>> That is a long time for something to happen. That is a long span of time. In Missouri, we have been experiencing really dry summers and droughts the past several years. Do you anticipate that could have an effect on them?
>> It certainly could. It is probably most critical 1-2 years after egg stage. Or maybe even a shorter amount of time than that. The youngest stage of a nymph or larvae is the most vulnerable to desiccation and drying out. [8:04.]
For example, Japanese beetles. Most of us who are gardeners or have flower beds really hate Japanese beetles. The good news with those is that their larvae are sort of naturally controlled during really dry summers. If we don't get ten inches of rain from July to September, then the Japanese beetle larvae don't do really well in the soil when they are really young.
I am sure there is something similar for periodicals and even our annual cicadas. If their nymphs are entering the soil in a really dry situation and the tree roots are dry what they want to feed on, then that could be problematic for them and reduce their populations I would imagine.
>> Okay, so now you have told us about their life cycle. We are going to be seeing them emerge here shortly. Tell us a little bit about the difference between the annual cicadas we see each summer versus the periodical. Is there a difference in the way they look?
>> Sure. So we have around 25 species of cicada in Missouri. But for most of us the ones most recognizable will be the dog day species, the annual ones; and then of course the periodicals.
The differences as far as appearances go the periodical cicadas are about half the size of most of our annual cicadas. They are black, orange and their wings are orange and they have red eyes. The periodicals are very striking in color.
The annual cicadas, or the dog days we see most often, they tend to be green and black. I have seen some that have really beautiful teal accents on them. They typically have white on their underside. They can be quite large, sometimes up to three times larger than a periodical. Most of the ones I notice around mid-Missouri are about three inches long with a body of about an inch and a half.
[10:10.]
They are really beautiful insects but compared to the periodical cicadas, they do look very different.
>> That is funny that the annual cicadas are bigger than the periodicals. For some reason, I had it in my head that the periodicals would be bigger.
>> Right, well, they live a lot longer so usually we equate living longer with being bigger, especially with trees and animals a lot of times. But in the insect world, that is not necessarily equated. Not necessarily the case at all.
>> So they will be feeding off of trees, correct?
>> For the most part, yes. They will pick something woody. A tree or a shrub. They have a straw-like mouth part that they will pierce into the tree and they will suck sap from the xylem of the tree. That is the water-conducting tissues. Yes, they do feed as adults. When they are nymphs underground, they are also feeding on the xylem of the woody or possibly grassroots when they are really little. Usually they will pick a woody species to feed from.
>> So they have a straw like mouth. Can they bite you?
>> That's a good question. You know, some species with straw-like mouth parts will stab you with their mouth parts. Cicadas are not really like that, though. I have been handling insects since I was about five years old. I love bugs. Of all the ones I have ever handled a cicada never once has bitten me in all this time. There are a few reports out there that if you let one sit on your hand long enough it may get used to you and think, "What is this?" and poke you with its mouth part to see what you are to see if you are indeed a tree or not. But as far as biting goes, no, they don't bite. They don't have the ability to sting at all.
You may see that a female has a needle-like apparatus on her hind end called an ovipositor. That is what she uses to lay her eggs, to pierce tree branches, make slits, and lay eggs. But that is not something she can sting you with.
>> Okay, I'm glad that you cleared that up. Let's clear up a few more cicada myths. Since they are eating from trees, are they bad for trees?
>> That is a really good question.
You know, there are a couple of different ways to look at it. As far as nature goes, these cicadas evolved here and any native tree that has lived here a long time has also evolved with cicadas. So I suspect this relationship has figured it out over time.
[12:46]
You know, what we expect to see during a periodical cicada year. Like I mentioned earlier, the females will be laying eggs in pencil-sized twigs. On a big mature healthy tree, you might see a lot of little brown patches across that canopy where females have laid eggs in those new twigs for the year. That may look terrible, but really it is just kind of like a light pruning every 13 years. It is something those trees are used to. Those small twigs will fall off eventually and really the tree should be fine in the long run so long as it is healthy.
The small trees that we might plant in our yard this spring are starting to become available at the big box stores right now. Those trees could very much be negatively impacted by cicada egg-laying. They have far fewer twigs to lose. A big tree has lots of twigs, and it won't lose them all. A small tree struggling to get established in your yard and put out a better root system needs all its twigs. Yes, cicadas could be damaging to new trees planted this year or in the last couple of years. Keep that in mind if you have a new tree in your yard you may think about netting it. Putting a fine mesh over it. Go to a craft store and get some touling or something like that or put some burlaps over it during the 4-6 weeks that cicadas will be out this year. Or if you are planning on planting a tree this year, consider putting that off until the fall or to next year.
[14:29]
You know a lot of tree species are available in the fall at the box stores. You could delay it until then.
>> It is just strictly tree species and woody shrubs. Any other plant that won't be susceptible?
>> Yes, mostly the woody things. I don't think that we will have to worry about anything else, just woody plants.
>> Another myth I would love to get your expert opinion on is . . . I had recently seen several articles online talking about cicada's urine stream. [Laughing.] It said that cicadas have a very strong stream of urine that can possibly spray you. Is there any truth to that?
>> Yes and no. I think that article that you specifically mentioned there has been some research that has looked into this phenomenon with cicadas. A lot of the information like this is related to species that come from Southeast Asia. When I looked into this for periodical cicadas or our annual cicadas in Missouri what I found was what I suspected to find. In all the years I have been around these insects, I never experienced this issue. I thought, well, have I just not seen this or is it not happening? Largely, this is not probably happening with our annual or periodical insects.
All insects that feed on xylem suck a lot of sap out of plants for not a lot of nutrients. That is the water-conducting tissue so there is not a lot of good nutrition in it. They end up feeding on a lot of sap. They have to get rid of that excess water, basically.
[16:26.]
They do essentially urinate, or pee that excess xylem out. In the case of our periodical and annual cicadas it is more of a drip. It is not an explosion of this honeydew or this sap excrement. It is nothing to be concerned about. When I lived out in the woods among a whole bunch of periodical and annual cicadas 13 years ago, I never noticed this being an issue even though there were thousands of these right outside my door.
What I have read is that if you go into the woods with a lot of periodical cicadas, expect to have a few drips here and there. It's really not urine like we would think of coming from a mammal. It is more like water. It really doesn't have much else in it besides water. It is not as nasty as you might think. Expect a few drips. If you go into southeast Asia, one of the rainforests there with this particular species of cicada native to the area, I read you should take an umbrella. It is far more of a soaking than a drip.
>> Can you imagine?
>> No, I can't. I don't think that will be an issue for us in Missouri, but it is something to keep in mind.
>> Like you said we would remember that. That would be a memory you would not forget.
>> Yeah I think that would be something that especially folks like myself really interested in insects and made these observations throughout my childhood and into adulthood. I have never noticed that. That would be strange for me to never notice that.
>> Something else I would like to have you speak on is that there has been a lot of media coverage regarding the emergence and that it is almost going to be a cicada apocalypse with the different broods and the areas. Speak on that.
[18:17.]
>> This started back in January. I got my first newspaper back in January when it was like -10 outside saying the cicada apocalypse is coming what can you tell us about it? I was like, "wait a second, I don't think that is exactly what is happening." The way a lot of these articles have been written does make it sound like this is a really unique year in that there will be way more cicadas than normal.
In a way, it is a unique year because there are two broods emerging. Brood 19 here in Missouri and about 14 or 15 other more southern and eastern states. Then brood 13, which is largely happening in northern Illinois, Wisconsin, and places upper midwest.
These two broods, yes, they are coming out in the same year but they are geographically separated. There is a ten-mile strip in central Illinois where they occur about ten miles apart but they don't technically overlap. With the new mapping apps and ways that people are tracking them, we may find that there is some overlap somewhere in there. But there is no overlap in Missouri at all. These are separate broods coming out in some separate places. We will just have the normal level of a whole bunch of cicadas in 2024.
>> You heard it here first, folks. Cicadas get a bad rep because they are so loud, right? They can be as loud as a chainsaw, correct?
>> Yes, a chorus of singing males could be as loud as about 100 decibels which yeah, that's a chainsaw, or a gas-powered leaf blower or lawnmower you are standing close to. It is pretty loud.
>> That is strictly their mating call?
>> Yep. That's the males calling trying to attract the females. The females do make some clicking sounds with their wings that signify to the male, "Yes, I like you, I will mate with you." Other than that, yes, it is just the males who are calling.
>> So they can get a bad rep because they are so loud because there are so many of them coming out, too. But, let's talk about why they are good. What are their benefits?
[20:24.]
>> I love to talk about why they are good. Yes, people in general are pretty alarmed by cicadas. They are large and kind of clunky and derpy when they fly. They have lots of endearing qualities. But if you don't like insects I can see why this would be sort of a scary event. I get it.
But from an ecology perspective, they are super cool. They are aerating the soil. They are tunneling down throughout the soil throughout their lifetime. In a lot of especially urban areas, their soils are very compacted and there is not much way that they are becoming aerated unless soil insects and animals are doing that. That is a cool thing about them.
When they die, there are lots of nutrients in their body. When they decompose, they fertilize the soil and that is a good thing. they are also contributing as a food source to all kinds of animals. There are lots of things that are going to do well this year because they will have periodical cicadas to eat. Some bird populations will probably do okay, especially wild turkey brood. They will be eating them this spring. Fish like them. They can be good bait for anglers. You know, fish will be all fat and happy because of cicadas. Lots of things eat these.
They are just really interesting too from an evolutionary standpoint. Gosh, there is hardly a more interesting insect in the world to be honest. They come out every 13 or 17 years depending on the species. How did they do that? How did they know? How did this evolve? Probably due to predator evasion. But man, that is really complex stuff right there. They only occur in the eastern half of the United States. They are nowhere else in the world. Periodical cicadas are unique to the eastern U.S. Which is super cool we have this crazy interesting insect that only occurs in our little part of the world. I think they are just super awesome.
>> We are special in that way, aren't we?
>> Yes!
[22:34.]
You know, all over the world species occur and there are really interesting things that occur in each place. This for us is one of those really cool things.
>> What can we do . . . you kind of touched on it earlier with maybe avoiding pesticides and insecticides in your lawn care. What are some other ways we can help them?
>> Yeah, so, I think there is going to be a big effort during the emergences of broods now and in the near future to map them and try to study them a little bit more and see which species are really occurring where and how are the populations doing. You know, if there is any kind of climate change issues going on in their populations. Because they don't come out very often they are hard to study.
Yeah, I think one of the things you can do as a community scientist to contribute to this effort. There is an app called Cicada Safari that will be widely used. I-Naturalist is another one you can use. But Cicada Safari will allow you to take pictures of the ones you are seeing so the species can be identified and then put a location to that and then it will be a point on the map. I think that would be really helpful for Missourians to do that. Even if you live in a big city and you think lots of people are doing this. It doesn't matter. We don't even know the distribution in St. Louis and how these are distributed around the greater St. Louis area. The more people who download this app and are recording these in their yards, the better information we will have for science. That is really awesome.
Yeah, again, avoid pesticide use in your yard as much as possible. Particularly, the insecticides because it has such a negative impact on the soil organisms in your yard. I think most people use that to try to prevent ticks or chiggers or maybe fleas in their yard. A lot of the insecticides that are used are not really effective on those particular pests and have more detriment to other things that are natively and naturally occurring there. Keep that in mind.
[24:52.]
>> Whenever I was younger, I had a little kiddie pool out in my backyard. I was swimming and I remember thinking to myself, "Man, these cicadas are so loud!" One was right on the back of my head, Robbie and I didn't realize it was a male calling right on the back of my head. I feel like almost everybody has a funny cicada memory or story.
>> There are a lot of people who have very core memories with one cicada experience.
You know, I don't have a specific bad experience for sure. The first time I remember seeing them was probably in the 1998 emergence. I believe we did have a double brood that year in the part of the state I grew up in southwest Missouri. We had both 13 and 17 years coming out then. There were a bunch of them.
I grew up float fishing a little creek called Flat Creek. I remember them just being in the water and being everywhere. It was my first recollection. I would have been in early high school/late middle school at that point. I remember thinking this is just crazy! I think I have some in my collection from that time period. It was the first, oh wow, these are cool. I never thought of these before. The other time they do have emerged I would have been 0 or 1, very young at that time. Yeah, really cool to realize what you are seeing for the first time. It wasn't until 2010 or 2011 emergence that I actually appreciated them. But yeah, I do have that core memory.
[26:35.]
>> Do you have any final thoughts that you would like to end on about cicadas or anything you would like people to know?
>> I think instead of being afraid of them or scared of them in general or annoyed by them. They will be calling for 4-6 weeks once they start emerging. Let's appreciate them this year. You know? Let's try to appreciate all the nature we can possibly appreciate. These especially. They are only out for a short period of time. Let's see it for the really cool thing that it is. Maybe we got to keep our windows shut to get some sleep at night during the early part of the spring or summer. But let's celebrate this. Let's call this cool.
There are some cicada recipes out there that some people are willing to try, others are not. I understand that. You don't need to eat it to appreciate it.
Let's have fun with this. Let's see this for the really neat thing that it is. I bought cicada earrings for all my entomology girlfriends. We will be rocking these gold cicada earrings this year. Us nerdy insect people are really excited about this. I hope that if everybody just has a fraction of that excitement and appreciation we can really celebrate this event in Missouri.
>> There is a lot happening. The solar eclipse and the cicada emergence.
>> Right! There are so many cool things going on. Let's not be annoyed by it. Let's say, "Hey, yeah, this is cool! Let's do this!"
[28:03.]
>> As Robbie mentioned, the U.S. will see two broods emerge this year - brood 19 which is the one we will see in Missouri, and brood 13 which will appear in parts of Iowa, Wisconsin, Illinois, Indiana, and possibly in parts of Michigan. Brood 13 is a brood of 17 year cicadas but will most likely not overlap geographically with brood 19 which is what we will have in Missouri.
One cool fact is that the last time these broods emerged in the same year was in 1803. That was when Thomas Jefferson was president and the same year the Louisiana Purchase was signed.
How do periodical cicada nymphs know its time to emerge after 13 or 17 years? One theory is that the nymphs' bodies may sense seasonal changes in the chemical composition of tree juices they eat from roots typically in the spring when trees leaf out. A sort of molecular clock in the cicadas is triggered by each leaf out period and once it has been triggered 13 or 17 times, the nymph will emerge the next time the soil warms to the trigger temperature.
This theory was corroborated in 2007 in Ohio when many periodical cicadas emerged a year early. The area had experienced warm January temperatures that caused many trees to bud out early but then they got zapped by a hard freeze in February and they had to leaf out again that spring. The two leaf-out periods apparently triggered the cicadas' molecular clocks which counted it as two "years."
Numerous annual cicada species occur in Missouri. Here are a few you may recognize. The first one is the Robinson Cicada which consists of slow pulses.
[Robinson cicada call.]
Another common species you may hear is the scissor-grinder cicada.
[Scissor-Grinder cicada call.]
The buzz saw cicada has a rough high-pitched buzz and will only call in the morning.
[Buzz-Saw cicada call.]
Finally here is the call of a periodical cicada.
[Periodical cicada call.]
Here is what hundreds of them sound like.
[Hundreds of periodical cicadas calling.]
[30:50.]
This was a topic I have been wanting to discuss on the podcast for a while. I am so happy we were able to learn more from Robbie, that we put some of those cicada myths to rest, and hopefully gave everyone a new perspective on these fascinating insects. Learn more on our website at missouriconservation.org.
Thanks again to forest entomologist Robbie Doerhoff, to Nature Boost producer Pat Graph, and to you for listening to another episode of Nature Boost!
I am Jill Pritchard with the Missouri Department of Conservation encouraging you to get your daily dose of the outdoors.
[Music playing.]
[End podcast.]