Tag Archives: cicada

Episode 226: Brood X Cicadas

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It’s the 2021 brood of 17-year cicadas! Thanks to Enzo (and several others) who suggested it!

Further listening:

Varmints! Podcast – “Cicadas”

Our local Brood X cicada (photo by me!):

The holes that cicadas emerged from (photo also by me):

Discarded cicada shells. My work keys and Homestar Runner keychain for scale:

Show transcript:

Welcome to Strange Animals Podcast. I’m your host, Kate Shaw.

This week we’re going to talk about cicadas, specifically the 17-year cicadas that you may have heard about in the news or in your own back yard, depending on where you live. Thanks to the several people who suggested the topic on Twitter, with special thanks to Enzo who emailed me about it.

I actually wasn’t going to do a cicadas episode because we already talked about cicadas way back in episode 28. We didn’t go into too much detail in that one, but Varmints! podcast did a great in-depth show about cicadas recently so I’ve been referring people to them, and check the show notes for a link if you don’t already listen to Varmints. Besides, I hadn’t heard any of the cicadas myself so I didn’t see what the big deal was.

Then I returned to work after taking some time off to take care of my cat Poe, who by the way is doing really well now and thanks for all the well wishes! The second I got out of my car, I heard them. The cicadas. Now, we get cicadas every year where I live in East Tennessee, so the sound is familiar to me and I actually like it. I find it soothing and the quintessential sound of summer. But this was something else. At only 8am the trees along the edge of campus were filled with what I can only describe as a high-pitched roar.

I went out at lunch and the sound was even louder. I got some audio, so here’s what a whole bunch of cicadas sound like when they’re calling at once.

[cicada sounds]

I also got pictures, which you can see in the show notes.

The cicadas emerging in such numbers this year are 17-year cicadas. They spend almost all of those 17 years as nymphs underground, where they eat sap from the roots of trees and other plants. At the end of the 17 years, when the soil is warm enough, they emerge from the ground and molt into their final form, the full-grown adult cicada!

The adult cicadas have wings but aren’t very good fliers. I can definitely attest to that because when I was taking pictures of them, I kept having to dodge as cicadas flew from bush to tree and either didn’t see me standing there or thought I was a weird tree or maybe just couldn’t maneuver well enough to avoid me. They’re pretty big insects, up to two inches long, or five cm, with gray or black bodies and orangey-red legs and eyes. The wings have pale orange veins.

The first cicadas to emerge are mostly males, in such numbers that predators get too full to care when the females emerge a few days later. That way more females survive to lay eggs. At first the cicadas that emerge still look like nymphs, but within about an hour they molt their exoskeleton and emerge as full adults with wings. They’re pale in color until the new exoskeleton hardens and the wings expand to full size, which takes a few days.

This, of course, leaves behind a cicada shell, which is the shed exoskeleton. When I was very small, I was terrified of cicada shells even though they’re just empty and perfectly harmless. They look scary because of those big pointy legs and big round eyes. You can frequently find cicada shells still stuck to tree bark, and it’s okay to pick them up and collect them if you like. The cicada doesn’t need it anymore. You can see the slit along the back of the shell where the cicada climbed out.

The emerged cicadas climb or fly into trees where the males start singing. Males produce their loud songs with a structure called a tymbal organ in their abdomen. The abdomen is mostly hollow, which helps amplify the rapid clicking of a pair of circular membranes. The clicking is so fast, up to 480 times a second, that humans hear it as a continuous buzzing noise and not individual clicks. Some cicada songs are louder than 120 decibels, which is the same decibel level as a chainsaw.

A reminder: this is what they sound like:

[more cicada sounds]

A female finds a male by listening to his song. After a pair mates, the female makes little cuts in twigs at the end of a tree branch, usually new-growth twigs because they’re softer. She lays her eggs in the cuts, then soon dies and falls to the ground.

Within a few weeks, all the adult cicadas have died. But around eight weeks later, the eggs hatch. The new nymphs are teensy, only a few millimeters long. They drop to the ground and burrow into the soil up to a foot deep, or 30 cm. There they stay for the next 17 years, growing larger very slowly until it’s time to emerge.

The current big group of cicadas consists of three species that look very similar. It’s called brood ten although I agree with Varmints who think it should be brood X because the Roman numeral ten is an X and every time I see it, I read it as Brood X. There are plenty of other cicadas, though, including some that emerge every 13 years instead of 17 years, and some that emerge every year or every few years.

Cicadas have been around for some 4 million years and most species live in tropical areas. Brood X is only found in the middle to northern areas of the eastern United States. It used to be even more widespread, but habitat loss has reduced its range considerably. Every time a forest is bulldozed to build a lot of houses, the nymphs underground either die outright or emerge later to find no trees to protect them and their eggs. Brood eleven went extinct in the 1950s, so even though there are millions of cicadas now, there may come a summer when no Brood X nymphs survive to emerge 17 years later.

The sudden emergence of thousands upon thousands of big loud insects in a short amount of time can be alarming, but cicadas are completely harmless to people, pets and other animals, and plants. They don’t eat as adults and they only make noise for a few weeks. They also don’t live everywhere. Even on the college campus where I work, the cicadas are only present in certain places. On the edge of the parking lot they’re everywhere. If I walk down to the far end of the duck pond, nothing. So if you happen to have Brood X cicadas in your yard or on your street, just remind yourself that that makes your home special and they’ll all shut up soon.

Of course, depending on where you live, in three years the enormous brood 19, called the great southern brood, will emerge throughout the southeastern United States, along with the smaller but just as loud brood 8, called the Northern Illinois Brood. But that gives you three years to buy a good pair of earplugs.

You can find Strange Animals Podcast at strangeanimalspodcast.blubrry.net. That’s blueberry without any E’s. If you have questions, comments, or suggestions for future episodes, email us at strangeanimalspodcast@gmail.com. If you like the podcast and want to help us out, leave us a rating and review on Apple Podcasts or Podchaser, or just tell a friend. We also have a Patreon at patreon.com/strangeanimalspodcast if you’d like to support us that way.

Thanks for listening!

Episode 028: Crawdads and Cicadas

Hello from Finland! While I’m far from home, I’m thinking of animals of my native land. So join me to learn about crawdads (aka crayfish aka crawfish aka freshwater lobsters aka everything) and cicadas!

A lovely blue crayfish from Indonesia:

Fite me

The giant Tasmanian crayfish:

A periodical cicada:

A cicada killer about to do horrible things to a cicada. Nature is disgusting.

Show transcript:

Welcome to Strange Animals Podcast. I’m your host, Kate Shaw.

For this week’s episode, which I’m putting together right before I leave for Finland on a madcap two-week adventure—okay, two weeks staying in the city of Helsinki while attending a conference and eating a lot of pastries—I’m going to look at two invertebrates that live close to home. The first is the crawdad. I’ve always wondered if those muddy holes near creeks and streams that we call crawdad holes around here are actually crawdad holes. Sometimes they’re nowhere near water. So I looked it up.

Yes, they are actually holes dug by crawdads. So that’s one mystery solved. The crawdad has a lot of different names depending on where you live: crayfish, crawfish, mountain lobsters, freshwater lobsters, mudbugs, and many other names. In Australia they may be called yabbies. There are a lot of species throughout the world, most of them in North America. Some also live in South America, Australia, New Zealand, Madagascar, Japan, and Europe. In fact, they live everywhere except Africa and Antarctica.

Crawdads are freshwater crustaceans and eat just about anything. Some species prefer running water, others like still water, but they all need clean water. If you find crawdads in the creek behind your house, you can be happy to know the creek has clean water—but don’t drink it, seriously. That’s a gross story for another time, but trust me, don’t drink untreated water.

Crawdads look like little lobsters and are closely related to them, and people do eat them. Some species are kept as pets in freshwater aquariums, although if you add them to your aquarium definitely make sure you’re not just providing your fish with a crunchy new snack, since a lot of fish eat crustaceans. Also keep in mind that many species of crawdad like to climb and dig so can make a mess of your nicely arranged tank.

One especially sought-after aquarium crawdad is a blue crayfish. Like blue lobsters, crawdads of normally drab colored species are occasionally found that are bright blue. It’s rare but not ridiculously rare. But there aren’t very many species that are always blue. This particular crawdad is beautiful, purplish pink on its body with blue and white claws and legs. But when they started showing up in the pet trade in the early 2000s, scientists didn’t have any idea what species they were. And the pet sellers weren’t telling where they were found.

After some digging, German researcher Christian Lukhaup traced the crawdads to a creek in Indonesia. It’s a new species, announced in 2015. We don’t know how widespread it is. Researchers worry it may be rare and threatened, and unfortunately most of the ones sold as pets have been gathered from the wild.

Many species of crawdads dig burrows. The bottom of the burrow ends in water, whether it’s a creek or the water table or just wet mud. Crawdads breathe through gills, but their gills are in their abdomen under their shell. As long as the gills are wet, the crawdad doesn’t have to actually be in the water to breathe. Crawdads are nocturnal animals and stay in their burrows during the day, then come out at night. The top of the burrow is usually surrounded by mud that the crawdad has pushed out of its hole. Other crawdad species live under rocks.

One of the smallest crawdad species is found in eastern Australia. It’s less than an inch long—usually only 12 to 18 millimeters in length, not counting its antennae—and is called a lake yabby or eastern swamp crayfish. It was only discovered a few years ago. It’s bluish-black and spends a lot of its time in its burrow, which usually reaches down to the water table so the yabby can survive during the dry season, when the shallow lakes and swamps where it lives may dry up completely.

New species of crawdad are found all the time. In 2009 a possible new species was reported in Tennessee. Two biologists, one from the University of Illinois and the other from Eastern Kentucky University, took a research trip to Shoal Creek, near the Tennessee-Alabama border. The very first crawdad they found, after only two hours of searching, turned out to be a new species—and it’s not exactly small. It’s some five inches long, which is roughly the length between the tip of my pinky finger and the base of my palm. I just measured out of curiosity. Most crawdads in the area are about half that length. DNA testing confirmed that it’s a new species and it was formally described in 2010. It’s related to another big crawdad found in Kentucky and Tennessee, which can grow up to 9 inches long. Both species appear to be rare and live under rocks in the deepest parts of a few streams and small rivers.

The biggest species of crawdad living is the Tasmanian giant freshwater lobster. It lives a long time, up to 60 years, if nothing eats it, and can weigh as much as 13 pounds and grow over two and a half feet long.

There are mysteries associated with the crawdad. For instance, most of Asia doesn’t have crawdads at all, but the ones that are found in Asia are more closely related to the crawdads of the southeastern United States than the crawdads of the southeastern United States are related to the crawdads of the northwestern United States. The northwestern U.S. crawdads appear more closely related to those found in Europe. But the big mystery is why there aren’t any crawdads in Africa.

Crawdads evolved from their marine ancestors around 200 million years ago. Around the same time, a big chunk of the earth’s land was smushed together in a big continent called Gondwana. The continents move around all the time—very, very slowly from a human perspective—due to plate tectonics. That’s why some of the animals found in, for instance, South America are closely related to animals found in Africa, because those two continents were once joined together. If you look on a map or globe you can even see that they fit together like puzzle pieces.

So crawdads evolved when Gondwana was just starting to break up into smaller continents. That explains why there are so many crawdads in different parts of the world—crawdads had time to spread out across much of Gondwana before it broke apart. But what would later be called Africa was right in the middle of Gondwana, and we know it had plenty of freshwater that crawdads could have lived in. Why didn’t crawdads populate that area?

It’s possible they did, but that as Africa moved farther toward the equator over millions of years, the crawdads died out. Crawdads prefer temperate climates—not too hot and not too cold. But there are two problems with that hypothesis. First, we haven’t found any crawdad fossils anywhere in Africa. By itself that’s not too unusual, since arthropods don’t fossilize well. They don’t have bones and their shells decompose relatively quickly. Plus, everything eats them so they don’t typically lie around undisturbed in the mud. But the other problem is more, well, problematic. Africa is a huge continent and most of it has never been that close to the equator. Parts of it have always been rainy and temperate, the perfect crawdad environment. And the island of Madagascar, which separated from Africa some 135 million years ago, does have crawdads. Plus, there are crawdads in parts of Australia that are much warmer than most of Africa. Plus, crawdads from the United States have been introduced into parts of Africa and have done so well they’re now an invasive species. What gives?

Africa does have a lot of freshwater crabs, which occupy the same ecological niche that crawdads do. It’s possible crawdads might have been outcompeted by the crabs. But freshwater crabs prefer tropical climates, not temperate. And in the parts of Africa where crawdads have been introduced, they’re actually thriving so well they’re endangering the native freshwater crabs.

So at the moment, we don’t know why Africa doesn’t have any native crawdads. The reason is probably more complicated than any one thing. For instance, if crawdads in one area were already dealing with freshwater crabs horning in on their food sources and territories, and the temperature was steadily increasing over the centuries, any little setback might have caused the crawdads to go extinct.

There are rumors of gigantic crawdads yet to be discovered. The remote Japanese Lake Mashu, formed some 11,000 years ago in the crater of a dormant volcano, is supposedly home to giant crayfish. There are rumors that trout poachers in 1978 and 1985 captured huge crawdads in the lake, although no pictures exist and no one is sure how big huge is supposed to be in this case. There is one report of a crawdad some two feet long found in the lake. A fisherman also reported seeing one that was three feet long, although he didn’t capture or measure it. As far as we know, the only crawdad living in the lake is a North America species introduced into the lake in the 1930s. It typically grows around 6 inches long, but a 1992 study of the lake’s crawdads didn’t find any larger than two and a half inches long.

During World War II, Australian marines patrolling swampland in Borneo found a crawdad that measured more than four feet long and weighed 49 pounds. It was caught in fresh water although it resembled a marine lobster. The marines nicknamed it Bagaton. The corpse was kept but so far it hasn’t been studied, but take this whole story with a grain of salt because I can only find two sources online that mention it at all.

While I was finishing up my crawdad research, I was on Twitter complaining that I didn’t quite have enough information for a full episode and I wasn’t sure what animal to pair it with. One of the hosts of Rumor Flies, an awesome podcast about rumors and myths, suggested cicadas. That made perfect sense to me, since cicadas are THE sound of summer in the southeastern United States.

I happen to love the sound of cicadas. Yes, they’re loud, but I find their chiming restful. Cicadas call during the day when it’s hottest, not at night—the insects you hear at night are usually katydids and tree crickets. This is what cicadas sound like.

[cicada sound—really you are not missing much, it’s just a rhythmic drone that I find soothing]

On the other hand, cicadas are creepy-looking although they’re harmless. When I was very small I was afraid of cicada shells, which are what’s left behind when a cicada hatches from its nymph form into its adult form. The adult cicada has wings and the male has a really, really loud song—so loud that he disengages his own hearing while he sings so he won’t deafen himself. Cicadas don’t have ears like mammals, they have a membraneous structure called tympana that detects sound. Males produce their loud songs with a structure called a tymbal in their abdomen. The abdomen is mostly hollow, which helps amplify the rapid clicking of the tembals. Some cicada songs are louder than 120 decibels, which is the same decibel level as a chainsaw.

There are a lot of cicada species around the world, but most live in the tropics. Seven species are known as periodical cicadas, which live most of their lives underground as nymphs, eating sap from the roots of certain trees, but emerge from underground as adults all at once. They sing, mate, lay eggs, and die in a matter of weeks, and the babies that hatch from their eggs don’t emerge from underground for another 13 or 17 years, depending on the species. Other cicada species have similar life cycles, but they don’t all emerge from underground at the same time—some emerge every summer while others remains as nymphs.

Cicadas are eaten by birds, bats, spiders, and even squirrels. There’s even a wasp called a cicada killer that preys specifically on cicadas—it captures a cicada, takes it back to its underground nest, and lays eggs in it. The eggs hatch and eat the cicada’s insides. BUT THE CICADA IS STILL ALIVE. I try not to think about insects too often. Cicada killers have black and yellow stripes like yellow jackets, but are much larger, up to two inches long. They will sting but only if provoked. They have to be big because cicadas are big insects, also about two inches long in most species.

Cicadas are edible, and are considered delicacies in many cultures. The females are meatier since the males have that hollow abdomen. In case you were wondering what to look for when you go shopping.

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