Speaker 1: Welcome to Stuff to Blow Your Mind production of iHeartRadio.
Speaker 2: Hey you welcome to Stuff to Blow Your Mind. My
Speaker 2: name is Robert Lamb.
Speaker 3: And I'm Joe McCormack, and we're back with Part three
Speaker 3: of our series on cicadas. Now, if you haven't heard
Speaker 3: the first two parts yet, you probably want to go
Speaker 3: check those out first. This is one where we lay
Speaker 3: a lot of the groundwork in the earlier episodes. This
Speaker 3: series was a little strange because we broke right in
Speaker 3: the middle of it after part one for a break
Speaker 3: that we had for a couple of weeks, came back
Speaker 3: last week with Part two, and here we are with
Speaker 3: Part three.
Speaker 2: Now.
Speaker 3: In Part one, we talked about the basics of cicada biology,
Speaker 3: their branch of the insect family tree, their life cycle, reproduction,
Speaker 3: the sounds they make, their bodies and organs, and the
Speaker 3: evolution of long underground developmental periods and timed emergences in
Speaker 3: the minority of SCA, a species known as periodical cicadas,
Speaker 3: which we have here in North America. We just had
Speaker 3: a very interesting and rare kind of coinciding emergence of
Speaker 3: two relevant broods of thirteen and seventeen year cicadas this
Speaker 3: year in twenty twenty four. The last time this coinciding
Speaker 3: emergence happened was like two hundred and twenty one years ago,
Speaker 3: so that's pretty cool. In part two of the series,
Speaker 3: we talked about the history of people being concerned with
Speaker 3: the question of whether periodical cicadas will bite them or
Speaker 3: sting them, or stuck out all their blood and leave
Speaker 3: them a thoroughly pumped frame. In the words of one
Speaker 3: New York Times article from the nineteenth century, they won't
Speaker 3: do that. Don't worry, it's not going to happen. And
Speaker 3: then we talked about the work of the American entomologist
Speaker 3: Charles Lester Marlott, who did important research mapping and cataloging
Speaker 3: the different broods of periodical cicadas in eastern North America.
Speaker 3: And today we're back to talk about more cicada stuff
Speaker 3: right now.
Speaker 2: Later on in this episode, we are going to be
Speaker 2: talking about a rather unique and by many standards, gnarly
Speaker 2: parasite of periodical cicadas, one that you may already be
Speaker 2: familiar with, even if it's like just surface level, because
Speaker 2: it's a rather outrageous example that sometimes breaks the surface
Speaker 2: of even late night coverage of science news. But before
Speaker 2: we're going to do that, we have a little cicada mythology,
Speaker 2: a little general cicada history to jump into here, right right.
Speaker 3: So I came across an interesting fact, which is that
Speaker 3: cicadas are featured in one of Plato's dialogues, one that
Speaker 3: I've read before, and I had no memory of this
Speaker 3: being a part of the discussion at all. And this
Speaker 3: dialogue includes a mythological origin story for cicadas. So the
Speaker 3: dialogue in question is Plato's dialogue The Feedress, and it's
Speaker 3: a story told by Socrates. So Fedris is a very
Speaker 3: famous dialogue of Plato. A lot of people read it
Speaker 3: in school. It covers a wide range of topics art, love, madness, reason, rhetoric, etc.
Speaker 3: It's the source of that famous chariot analogy where Socrates
Speaker 3: describes the soul as a chariot pulled by two horses
Speaker 3: with very different temperaments, each representing different forms of passion
Speaker 3: and instinct within human nature. And then the charioteer is
Speaker 3: sort of the reasoning part of the soul that must
Speaker 3: tame the two horses and steer them together on the
Speaker 3: path of truth and righteousness. Even though they want to
Speaker 3: go in different directions on their own. But anyway, the
Speaker 3: story of the cicadas is not part of the Chariot analogy.
Speaker 3: It comes partially due to the setting of the dialogue.
Speaker 3: So in this dialogue, Socrates and this other guy, Feedris
Speaker 3: are outside the city of Athens, and it is said
Speaker 3: that they're sitting on the banks of a stream having
Speaker 3: a good old philosophical conversation, and in the background cicadas
Speaker 3: are singing. They make reference to this a couple of
Speaker 3: times in the dialogue, and then Socrates starts imagining that
Speaker 3: if he and Fedris were not doing what they're doing,
Speaker 3: not having a philosophical conversation, but we're instead just lying
Speaker 3: by the river listening to the cicada song, he says
Speaker 3: that the cicadas would have a right to laugh at
Speaker 3: them for being lazy and unvirtuous. But since the cicadas
Speaker 3: know that Socrates and Fedris are instead discoursing on philosophy,
Speaker 3: trying to get to the truth, and not being just
Speaker 3: lulled to sleep by their song, he says quote, they
Speaker 3: may perhaps, out of respect, give us of the gifts
Speaker 3: which they receive from the gods, that they may impart
Speaker 3: them to men, And then Fedris says, what gifts are
Speaker 3: you talking about? What gifts to cicadas have to give
Speaker 3: two men from the gods? And here I'm going to
Speaker 3: read socrates response. This is the Benjamin Joet translation orig
Speaker 3: generally renders the name of the insect here as grasshoppers.
Speaker 3: But it seems to me generally agreed that this story
Speaker 3: is referring to cicadas. So I've gone through the passage
Speaker 3: and replace the word grasshopper with cicada. Excellent, Socrates says,
Speaker 3: A lover of music like yourself ought surely to have
Speaker 3: heard the story of the cicadas, who are said to
Speaker 3: have been human beings in an age before the muses.
Speaker 3: And when the muses came and song appeared, they were
Speaker 3: ravished with delight and singing, always never thought of eating
Speaker 3: and drinking, until at last, in their forgetfulness, they died.
Speaker 3: And now they live again in the cicadas. And this
Speaker 3: is the return which the Muses make to them. They
Speaker 3: neither hunger nor thirst, but from the hour of their
Speaker 3: birth are always singing and never eating or drinking. And
Speaker 3: when they die, they go and inform the Muses in heaven,
Speaker 3: who honors them on earth. They win the love of
Speaker 3: terpsickery for the dancers by their report of them, of
Speaker 3: Erato by the lovers, and of the other muses, for
Speaker 3: those who do them honor according to the several ways
Speaker 3: of honoring them, of Calliope, the eldest muse, and of Urania,
Speaker 3: who is next to her, for the philosophers, of whose
Speaker 3: music the cicadas make report to them. For these are
Speaker 3: the muses who are chiefly concerned with heaven and thought
Speaker 3: divine as well as human, and they have the sweetest
Speaker 3: utterance for many reasons. Then we ought always to talk
Speaker 3: and not to sleep at mid day. So cicadas, according
Speaker 3: to this story, were humans before the time the muses
Speaker 3: came into being. And when the muses came to exist,
Speaker 3: they brought with them music. They brought song, and then
Speaker 3: the pre muse humans were so enraptured by the invention
Speaker 3: of music that they entertained themselves to death. They listened
Speaker 3: to music without eating or drinking until they just died.
Speaker 3: And I guess made me to made music. Listen to music,
Speaker 3: it's all song and dance, until they just straight up died.
Speaker 2: This is why you have concessions.
Speaker 3: Yeah, exactly right, Yeah, but then but then the muses
Speaker 3: allow them to live again as cicadas and to sort
Speaker 3: of to be snitches for the muses, you know, to
Speaker 3: be the muse's earthly surveillance team, to kind of like
Speaker 3: hang out down here and spy on people and see
Speaker 3: who's honoring the muses properly and who is not honoring them.
Speaker 3: And I was thinking about this and how it seems
Speaker 3: like it's kind of interesting to me to see how
Speaker 3: norms of moral and intellectual virtue are kind of different
Speaker 3: in our culture versus what Socrates is proposing here, because
Speaker 3: it seems like Socrates is talking like it's just rather
Speaker 3: obvious that sitting silently in nature, maybe falling asleep by
Speaker 3: a river, listening to the insects vocalized, is something akin
Speaker 3: to a vice. At the very least. It's like intellectually
Speaker 3: lazy and not worthy behavior in the view of the
Speaker 3: intellectual muses like Calliope and Urania, who are muses of
Speaker 3: things like philosophy and eloquence and astronomy and stuff, you know,
Speaker 3: the muses of learning. And it's thought that these muses
Speaker 3: would certainly see it as better for people to be
Speaker 3: engaged in philosophical argumentation. And this is to the extent
Speaker 3: that in the comment right before this selection, when Socrates
Speaker 3: is talking about, like, you know, he's first talking about
Speaker 3: the cicadas looking at them and judging what they're doing.
Speaker 3: Socrates says, quote, but if they see us discoursing like Odysseus,
Speaker 3: sailing past them, deaf to their siren voices, they may, perhaps,
Speaker 3: out of respect, give us of the gifts which they
Speaker 3: receive from the gods, that they may impart them to
Speaker 3: men okes. I read the last part of that.
Speaker 2: Yeah, all right, So the cicadas are singing, they're busy,
Speaker 2: enraptured by song, and if we're not living our lives
Speaker 2: to like full creative musical extent that we could, then
Speaker 2: they are going to shame us, and they're going to
Speaker 2: laugh at us. But if we're busy talking, having philosophical discussions,
Speaker 2: then they might just give us a little gift here
Speaker 2: and there.
Speaker 3: Right, they'll go tell the muses that we've been good.
Speaker 2: Yeah, we'll get a boon, Okay, okay.
Speaker 3: But it's interesting that kind of difference in expectations because
Speaker 3: I think among I don't know, probably a lot of
Speaker 3: people sitting listening to this podcast right now, a lot
Speaker 3: of us today, I think probably think that sitting quietly
Speaker 3: in nature and listening to the bugs, sitting by a river,
Speaker 3: maybe dozing off is an activity that would be more
Speaker 3: associated with like virtue and seriousness and discipline and so forth,
Speaker 3: things like that today, And I don't think that would
Speaker 3: be widely seen as like a less intellectually serious type
Speaker 3: of activity than arguing about the nature of reality and
Speaker 3: a philosophical discourse. It seems like, you know, every yahoo
Speaker 3: an out there wants to argue about what's true. You know.
Speaker 2: Yeah, you can imagine like Socrates busting into my new
Speaker 2: yoga class that I go to and saying, why aren't
Speaker 2: you talking about philosophy? What are you doing laying about
Speaker 2: doing stretches, being in the now? Stop it?
Speaker 3: So, I don't know, maybe our norms today extend from
Speaker 3: the idea that like, there are access to easier entertainments
Speaker 3: than like listening to the cicadas or something, and so
Speaker 3: if you're like really intellectually lazy, you're like watching TV
Speaker 3: or something instead of, maybe to the ancient Greek sitting
Speaker 3: and listening to the cicadas and dozing off by the river.
Speaker 3: That's the equivalent of watching TV or something.
Speaker 2: I don't know, Yeah, I mean it also sounds like
Speaker 2: he's kind of shaming folks for being inactive and resting
Speaker 2: a little bit during like the hottest part of the day,
Speaker 2: you know. So I don't know, but I think you're right. Yeah,
Speaker 2: this does kind of turn a lot of our modern
Speaker 2: ideals and aspirations about everything from I mean really everything
Speaker 2: from midday rest and you know the idea of taking
Speaker 2: the siesta to doing like a mid day exercise, mid
Speaker 2: day yoga, meditation, or even just a mid afternoon nap. Yeah.
Speaker 3: But I also like the idea that this mythology of
Speaker 3: cicada origins incorporates a couple of things. I mean, one
Speaker 3: is the interesting, like you know, the entertain themselves to
Speaker 3: death concept. It's not unique like that. There are other
Speaker 3: stories of similar kind of people who get so excited
Speaker 3: by some kind of activity that they forget to live.
Speaker 3: And so there's that aspect. But also I like the
Speaker 3: idea of cicadas as surveillance devices, that they are down
Speaker 3: here spying on us for the gods, because it can
Speaker 3: sort of feel like that, right, like the way that
Speaker 3: you go into their space and you can't see them,
Speaker 3: but you imagine they can see you. It often feels
Speaker 3: this way with various kinds of bugs that make sounds
Speaker 3: in the night, whether it's cicadas or not, because you
Speaker 3: might have that experience of, say, going into the woods
Speaker 3: at night and there bugs making sound, But then the
Speaker 3: bugs get quiet, so you realize they're aware of your
Speaker 3: presence and reacting to it, but you can't see any
Speaker 3: of them. So it does feel like a kind of
Speaker 3: surveillance situation.
Speaker 2: Yeah. Yeah, you're literally bugged right, Oh yeah, yeah, And
Speaker 2: there is like we've been discussing with the cicadas like that,
Speaker 2: just that feel of them in their masses, like the
Speaker 2: rise and fall of their cadence. It it does have
Speaker 2: this very surreal feel to it. It feels like, like
Speaker 2: I say, I often think about it as just being
Speaker 2: like part of the midday heat. You know. It's it's
Speaker 2: something that's difficult for the human mind to sort of
Speaker 2: fathom as what it is, like, all these individual cicadas
Speaker 2: making little sounds. It feels like something much bigger than
Speaker 2: us in many ways.
Speaker 3: Yeah, almost like the gods are in on it. Yeah.
Speaker 3: But if there are some aspects of cicada biology that
Speaker 3: might make them feel like an envoy of the muses
Speaker 3: or some kind of you know, allied with the heavens.
Speaker 3: There are other ways in which you can learn things
Speaker 3: about cicadas that really make them like they were cursed
Speaker 3: by the devils, like if Hades has it out for them, Yeah.
Speaker 2: Yeah, yeah, cursed by the gods or you know, who
Speaker 2: are we to question the strange creations the lonely perfection
Speaker 2: of the gods. I want to talk a bit about
Speaker 2: one very notable parasite of cicadas in general, but there's
Speaker 2: a lot of emphasis on the varieties that target are
Speaker 2: periodical cicadas. So we've already discussed the unique life cycle
Speaker 2: of the periodical cicadas and some of the ideas concerning
Speaker 2: why they spend thirteen or seventeen years underground in this
Speaker 2: low metabolism subterranean larval form and then eventually erupt and
Speaker 2: engage in this noisy litter, producing a feast for predators
Speaker 2: but also very vital reproductive cycle of their lives. And
Speaker 2: one of those one of the ideas behind this is
Speaker 2: that they do this in order to outmaneuver various predators
Speaker 2: and parasites that otherwise might sync up with their life cycle.
Speaker 2: Now We've already admitted though that this may seem to
Speaker 2: work in some cases, but periodical cicadas have not been
Speaker 2: able to outmaneuver everything. And of course we also discussed
Speaker 2: how like, basically the idea of everyone emerging at once
Speaker 2: and reproducing also is to just overwhelm predators. They can't
Speaker 2: possibly eat everything, and any given species are going to
Speaker 2: live in some degree of equilibrium with its parasites, with
Speaker 2: its predators and so forth.
Speaker 3: This actually would be a good place to mention something
Speaker 3: interesting I came across in research since the last episode,
Speaker 3: which is I was looking for more information about the
Speaker 3: actual direct evidence for predator saciation in periodicals, and again,
Speaker 3: satiation is the evolutionary strategy we've been talking about. It's
Speaker 3: one hypothesized reason for these mass periodical emergencies, where the
Speaker 3: idea is, again there are more cicadas than all the
Speaker 3: predators that eat them can possibly eat all at the
Speaker 3: same time, So the eating capacity of the predators and
Speaker 3: also the parasitizing capacity of the parasitoids is overwhelmed. There's
Speaker 3: too much all at once, and thus each individual cicada's
Speaker 3: chances of suffering from predation are much lower. So I
Speaker 3: was like, well, what is the actual evidence for predator saciation,
Speaker 3: and so I found an interesting study. It was won
Speaker 3: by Richard Carbond done in the journal Ecology in nineteen
Speaker 3: eighty two called Increased reproductive success at high densities and
Speaker 3: predator satiation for periodical Cicadas. In the study, the researchers
Speaker 3: combed over selected areas during periodical cicada emergencies and collected
Speaker 3: cicada wings, which was an interesting strategy. Basically, they were
Speaker 3: trying to look at bird predation on cicadas and they
Speaker 3: discovered that wings are often discarded when birds eat cicadas,
Speaker 3: so bird chomps the cicada, the wings fall off, and
Speaker 3: so they collected wings in these areas to allow the
Speaker 3: researchers to form rough estimates of how many cicadas are
Speaker 3: eaten by birds within the area at a given time period.
Speaker 3: And what the author here found was interesting. The number
Speaker 3: of wings increased its sites with more bird density, so
Speaker 3: cram more predators into a region, more cicadas get eaten,
Speaker 3: but the number of wings did not increase at sites
Speaker 3: with more cicada density, so more things to eat doesn't matter.
Speaker 3: Nothing more gets eaten. In other words, if you put
Speaker 3: more cicadas in the area, and the bird population remains
Speaker 3: the same. No additional cicadas get eaten by birds, because
Speaker 3: the birds are already eating their fill. There's already more
Speaker 3: than they possibly can get to, and thus each end
Speaker 3: of jual cicada's chance of being eaten goes down. That's
Speaker 3: the predator satiation scenario. The predators are full. But of
Speaker 3: course the real danger in the bird predation scenario would
Speaker 3: be if the birds caught on to this in some
Speaker 3: way and increased their numbers to take advantage of this
Speaker 3: massive amount of leftovers. Maybe if they had more offspring
Speaker 3: and increase their population density at the time when cicadas
Speaker 3: were available, or if more birds migrated to the area
Speaker 3: at the time when cicadas were available, or something like that.
Speaker 3: So if the number of predators goes up, the safety
Speaker 3: advantage for cicadas goes down. And this is another reason
Speaker 3: that it's hypothesized that the thirteen or seventeen year period
Speaker 3: is helpful. The ideas this makes it harder to track with,
Speaker 3: like the predators can't sync up their migration or reproductive
Speaker 3: or whatever cycles to be in the right place at
Speaker 3: the right time to take advantage of all the cicada biomass.
Speaker 3: So sorry for the digression, but I had discarded cicada
Speaker 3: wings on the brain, So that'll bring us back to
Speaker 3: you were saying that the cicadas are not able to
Speaker 3: outmaneuver everything, and there's one organism in particular that is
Speaker 3: a parasite that has adapted to periodical cicadas.
Speaker 2: That's right. This organism is Masospora cicadia. And this is
Speaker 2: a fungal pathogen that was discovered by American mycologist and
Speaker 2: botanist Charles Horton Peck back in eighteen seventy nine, who
Speaker 2: is a pretty important figure in North American mycology around
Speaker 2: the turn of the twentieth century. I think like thousands
Speaker 2: of different species of fungus were described by him, North
Speaker 2: American fungo, fung gui and he was also the New
Speaker 2: York State Botanist from eighteen sixty seven through nineteen fifteen.
Speaker 2: So I went back and I was reading Peck's original
Speaker 2: report on the fungus in question, back in eighteen seventy
Speaker 2: nine's thirty first Annual report on the New York State
Speaker 2: Museum of Natural History by the Regions of the University
Speaker 2: of the state of New York.
Speaker 3: What state was that in?
Speaker 2: Well, New York, of course. But the paper is quite readable,
Speaker 2: and it describes most of the key features of the
Speaker 2: parasitic infection of periodical cicadas, and does so redis succinctly.
Speaker 2: So I'm going to read a passage from it here.
Speaker 2: But basically he starts off by mentioning that fungal parasites
Speaker 2: of insects are known and are quite common. So this was,
Speaker 2: in and of itself nothing new. And certainly, if you
Speaker 2: pay any attention to science news, you have run across
Speaker 2: various examples of those various fungal parasites that depend on insects,
Speaker 2: and in many cases, like you don't seem to alter
Speaker 2: their biology and or behavior. You know, puppet masters if
Speaker 2: you will.
Speaker 3: Yeah, we've done episodes in the past about Ohiocordyceps fungus
Speaker 3: specifically praying on insects, and I don't know if this
Speaker 3: has overlapped with that or not, but.
Speaker 2: There are some I think it it lines up in
Speaker 2: places though there are some mysteries that remain, and I
Speaker 2: think there's still you know, there's still certain mysteries that
Speaker 2: remain with with other examples of fungal parasites. We're still
Speaker 2: learning a lot. There's still some things that are more
Speaker 2: in the realm of hypothesis that sometimes maybe get picked
Speaker 2: up and carried into the mainstream press a little more
Speaker 2: settled than they actually are. We're still learning a lot.
Speaker 2: At the time of this writing, though, this was a
Speaker 2: new one and it was based on some specimens that
Speaker 2: had been sent to Peck from New Jersey. So in
Speaker 2: this text he writes, the fungus develops itself in the
Speaker 2: abdomen of the insect and consists almost wholly of a
Speaker 2: mass of pale, yellowish or clay colored spores, which to
Speaker 2: the naked eye has the appearance of a lump of
Speaker 2: whitish clay. The insects attacked by it becomes sluggish and
Speaker 2: averse to flight, so that they can easily be taken
Speaker 2: by hand. After a time, some of the posterior rings
Speaker 2: of the abdomen fall away, revealing the fungus within. Strange
Speaker 2: as it may seem, the insect may and sometimes does
Speaker 2: live for a time even in this condition. So that's
Speaker 2: some of like the basic observable aspects of this. And
Speaker 2: I don't believe I've ever looked at a cicada specimen
Speaker 2: with this scenario. I mean, I've you know, in the
Speaker 2: course of my life, I've I've nudged quite a few
Speaker 2: with my feet, you know, or or accidentally stepped on one.
Speaker 2: But I don't know if I've noticed this before. But basically,
Speaker 2: if you look at the pictures and footage and so forth,
Speaker 2: you will find adult cicada specimens, so winged specimens that
Speaker 2: have they have a situation where their abdomen has seemingly
Speaker 2: like turned to like chalky clay. You know, It's almost
Speaker 2: like their abdomen has internally petrified and then begins to crumble,
Speaker 2: with the outer ridges falling away from it.
Speaker 3: And yet the insect is at this point still alive,
Speaker 3: which is gross and weird to think about, right.
Speaker 2: Yeah, yeah, And as as Pack pointed out, you know,
Speaker 2: there are many observ do say that they seem to
Speaker 2: be more sluggish. I'll get into a little bit about
Speaker 2: that in a bit. But then on the other hand,
Speaker 2: they can also seem very energetic. So there's a lot
Speaker 2: going on here. And again there seems to be a
Speaker 2: lot of investigation still ongoing in various hypotheses regarding exactly
Speaker 2: what's going on, and then there's certain things that are
Speaker 2: just unknowable. You know, we cannot know the mind of
Speaker 2: the cicada.
Speaker 3: Yeah, it's just hard to imagine, like a mammal equivalent,
Speaker 3: Like if a human, like the low from your belly
Speaker 3: button down, that like is just gone, that fell off,
Speaker 3: and there's just like a big lump of white clay
Speaker 3: chalk kind of gunk sticking out of the bottom of
Speaker 3: your torso and you're still alive and moving around, but
Speaker 3: maybe sluggish.
Speaker 2: Yeah, yeah, leaving a trail of spores behind you and
Speaker 2: occasionally rubbing spores against other humans and infecting them. So
Speaker 2: I looked to a couple of different recent sources about
Speaker 2: the organism in question. Rachel treisman Over at MPR covered
Speaker 2: M Cicadina earlier this month, providing a nice overview of
Speaker 2: the organism. Essentially, it's still quite active and one of
Speaker 2: the reasons, of course, you know, we have these emergencies,
Speaker 2: these these two major broods, and so there are a
Speaker 2: lot of periodical cilicadas out there, and there's gonna be
Speaker 2: a certain amount of infected periodical circados to check out.
Speaker 2: So I'm gonna have to keep an eye open for
Speaker 2: these now. And certainly listeners write in if you find one.
Speaker 2: But it's interesting that the chalky abdomen that we've been
Speaker 2: describing it does kind of match up with the name
Speaker 2: of the organism. So massospora essentially means spore grinder, alluding
Speaker 2: to the fact that it would almost seem that the
Speaker 2: hind parts of the cicada have been again petrified and
Speaker 2: then pulverized or like grated, you know, like parmesan cheese
Speaker 2: or something.
Speaker 3: Oh not the not the shreds, but the dust. Yeah,
Speaker 3: using that side of the greater box. Yeah, you want
Speaker 3: the dusting, right, Yeah. So it's try some points out here. M.
Speaker 3: Cicadina employees is active host transmission, So the cicada again
Speaker 3: remains alive and active, though its behavior may be altered
Speaker 3: by the fungus, or i mean, the behavior seems to
Speaker 3: be altered by the fungus. Exactly how it's being altered,
Speaker 3: you know, if we're talking physically, chemically, so forth. There's
Speaker 3: a lot of back and forth over that. But all
Speaker 3: of this does seem to serve to optimize the distribution
Speaker 3: of the spores. So let's break down the live cycle.
Speaker 3: And I'm also drawing on a specialized fungal parasite hijacks
Speaker 3: the Sexual Signals of periodical Cicadas by koli at All,
Speaker 3: published in scientific reports back in twenty eighteen. Okay, so
Speaker 3: remember the life cycle of the periodical cicada. So it
Speaker 3: begins here with the emergence of those periodical cicadas. They're
Speaker 3: coming up through the ground and as this occurs, some
Speaker 3: of the individuals become infected with this this fungal parasite. Now,
Speaker 3: the exact number, estimates are maybe five percent of the
Speaker 3: population total according to Treisman, but the number can reach
Speaker 3: twenty to thirty percent in different areas. So you know,
Speaker 3: you might have a like a major hub, a major
Speaker 3: area where they're the higher.
Speaker 2: Rate of infection. But overall it's thought that maybe this
Speaker 2: is like five percent of the periodical cicada population. Okay,
Speaker 2: so these are already these ones that are emerging and
Speaker 2: become infected as they emerge. More than that at a second.
Speaker 2: In a second, these are stage one infected cicadas, and
Speaker 2: they produce haploid condiospores that can infect other active adult cicadas.
Speaker 2: Later on in the emergence, the cicadas infected by these
Speaker 2: spores becomes stage two cicadas and stage two infected cicadas,
Speaker 2: and they produce diploid resting spores. These spores fall to
Speaker 2: the ground where they can actually seemingly lay dormant in
Speaker 2: or on the soil for thirteen to seventeen years, though
Speaker 2: they can activate pretty much right away, but they're there
Speaker 2: on or in the soil, and they infect emerging nymphs.
Speaker 3: Ah okay, So spores that can just lie in wait
Speaker 3: for thirteen or seventeen years get around the periodical adaptation
Speaker 3: in a way that the population of predatory animals could not.
Speaker 3: You can't have a big enough population of birds to
Speaker 3: eat all of the cicadas just waiting around for thirteen
Speaker 3: years for them to come back. They'd starve in the meantime.
Speaker 3: But if you're a spore, you can just sit there
Speaker 3: and wait.
Speaker 2: That's right, like a little landmine, ready to go off
Speaker 2: and infect one of those nymphs when it begins emerging
Speaker 2: for the final period of the life cycle. So that's
Speaker 2: the basic cycle. But then there are the details of
Speaker 2: what the infection does. The major thing, of course, is
Speaker 2: what we've already talked about. This is the distension and
Speaker 2: loss of these abdominal segments, which includes the genitalia in
Speaker 2: both sexes, So, in other words, turns the entire inside
Speaker 2: of the abdomen into one big mass of spores, it
Speaker 2: loses any of its reproductive organs, and then all of
Speaker 2: this becomes exposed as the outer abdomen eventually ruptures and
Speaker 2: begins to fall away, and they turn into crawling, flying
Speaker 2: spore crop dusters.
Speaker 3: So they're just crawling around great in the spiky side
Speaker 3: of the box grade or just dusting everything.
Speaker 2: That's right, that's right. And this is where the topic
Speaker 2: of behavioral adaptation comes into play. To what degree is
Speaker 2: the parasite also manipulating behavior of the infected cicada. So yeah,
Speaker 2: a lot of coverage points to this, but when you
Speaker 2: get into some of the papers, such as the one
Speaker 2: I just cited, there seems to be a lot more
Speaker 2: uncertainty because, on one hands, cooly I all point out
Speaker 2: some of the apparent changes in behavior may be brought
Speaker 2: on as much by physical changes due to the infection.
Speaker 2: For instance, they cite that infected cicadas often remain more stationary,
Speaker 2: make shorter flights, and drag their abdomens when they want
Speaker 2: trailing spores. Of course, and these changes could in large
Speaker 2: part be brought on by the damage they've sustained via
Speaker 2: the infection. Again, they've they've they've sustained a lot of
Speaker 2: damage here. They're they're abdomen has been transformed into just
Speaker 2: a sport a crumbling spor sack with the flesh, you know,
Speaker 2: crumbling off around it. And they also point out that
Speaker 2: stage ones tend to walk and trail more, while Stage
Speaker 2: twos tend to fly and spread. So, you know, I
Speaker 2: guess the idea here is Stage ones are trailing and
Speaker 2: around in you know, on branches and areas where other
Speaker 2: cicadas are going to gather, while the stage twos they're
Speaker 2: flying around because their spores are you know, mint if
Speaker 2: we we dare use that word to to to fall
Speaker 2: to the ground where they will be useful later on
Speaker 2: when nymphs emerge. But they stressed that this could be
Speaker 2: behavioral manipulation as well. Uh So, here's where it gets
Speaker 2: even more interesting. This, according to Coolie at All quote,
Speaker 2: stage one massive spora infection, which produce spores that are
Speaker 2: spread directly to other adult cicadas, cause males to wingflick
Speaker 2: in response to the calls of other males with the
Speaker 2: same species specific timing used by sexually receptive magicicada females.
Speaker 2: These novel wing flick responses are attractive to normal, uninfected
Speaker 2: males who repeatedly attempt to copulate with the disease males.
Speaker 2: So these copulations are going to be unfruitful, be it
Speaker 2: male female or male male matches, because remember the genitals
Speaker 2: are all destroyed anyway. But it results in a mimicry
Speaker 2: of receptive mates, and so they end up, you know,
Speaker 2: rubbing their abdomens together. At least, you know, you're getting
Speaker 2: those spores moved around, the scores spread, and that, at
Speaker 2: least to the fungus is what matters. And in this
Speaker 2: the fungal pathogen acts as a sexually transmitted pathogen.
Speaker 3: Okay, so this is an example of how it may
Speaker 3: be the fungus, as we've seen in other examples of
Speaker 3: a fungi that infect insects. Because remember, like the other
Speaker 3: example I mentioned the Ohio Cordyceps fungus which infects ants.
Speaker 3: I think that's the one that causes them to you know,
Speaker 3: it makes them like climb up to the top of
Speaker 3: a you know, some overhanging thing, and they like glatch
Speaker 3: onto it, and then they grow these bodies out of
Speaker 3: like a spike out of their head or somewhere out
Speaker 3: of their bodies and rain down spores on the other
Speaker 3: ants below. That's an example of what is thought to
Speaker 3: be a kind of behavior manipulation, and this looks more
Speaker 3: like a direct behavior manipulation, and not just the insects
Speaker 3: responding to changes in their body right.
Speaker 2: But with one potential caveat when we get to the
Speaker 2: chemical aspect of what may or may not be going on. Okay, okay,
Speaker 2: so okay, So we have these stage ones, We have
Speaker 2: these males on their branches, twitching their wings like their females,
Speaker 2: attracting other males. Stage two infections, though, do not cause
Speaker 2: this behavior. And again the stress seems to be on
Speaker 2: these these stage two infected cicadas spreading these spores to
Speaker 2: the ground where they will in time infect emergent nymphs.
Speaker 2: So this is where we get to the chemical aspect
Speaker 2: of it, and the idea that there's chemical manipulation going
Speaker 2: on as well by the parasite. So as pointed out
Speaker 2: in Triisman's article, the fungus has also been found to
Speaker 2: produce a stimulant called cathinone a plant associated amphetamine in
Speaker 2: four infected cicada populations, and then elsewhere we have infected
Speaker 2: populations of annual cicadas which were found to contain the
Speaker 2: hallucinogen psilocybin, according to a study published in Fungal Ecology
Speaker 2: back in twenty nineteen.
Speaker 3: Wait a minute, so it's this fungus is getting its
Speaker 3: hosts sort of caffeinated and on mushrooms.
Speaker 2: Essentially, Yeah, there is. So one of the big caveats
Speaker 2: here is that, again, we can't know the mind of
Speaker 2: a cicada. Right, A lot of headlines that you know,
Speaker 2: you know, at least jokingly have some fun with the
Speaker 2: idea that the cicadas are high out of their minds.
Speaker 2: We don't really know if they're high, but we can't help.
Speaker 2: But but but look at these chemicals in these cicadas
Speaker 2: and wonder, like, what the purpose is here? What is
Speaker 2: it doing? And to what degree is it affecting behavior?
Speaker 2: And there seems to be a strong case for.
Speaker 3: That, right, I apologize for over anthropomorphizing by implication.
Speaker 2: No no, no, no, But you're you're also onto the
Speaker 2: right track too. So I couldn't find as much about
Speaker 2: the psilossignment aspect and again, those are going to be
Speaker 2: annual cicadas and not periodicals. But there has been more
Speaker 2: hypothesized about the stimulants in the periodical cicadas, so some
Speaker 2: have speculated that these do in fact enhance cicada libidah
Speaker 2: or to some degree make this caya not particularly care
Speaker 2: about the physical changes they're undergoing. But the other main
Speaker 2: interpretation is that that that cathinone the stimulant is what
Speaker 2: causes that rapid wing movement, So like, oh, like, why
Speaker 2: are they moving their wings rapidly and mimic and ultimately
Speaker 2: mimicking receptive females. It could be because they're just jacked
Speaker 2: up on this uh, this this particular stimulant in their
Speaker 2: bodies and it's causing the wing flapping, which then causes
Speaker 2: this additional behavioral change.
Speaker 3: So it's possible the stimulant causes just sort of a
Speaker 3: nervous behavior, like a flexing kind of behavior, which happens
Speaker 3: to resemble mating signals, which attracts other males who hopefully
Speaker 3: will get infected by this fungus from the fungus's perspective.
Speaker 2: That's right. Again, there's a lot there's a lot more
Speaker 2: to consider there, and there seems to be a lot
Speaker 2: of work still going on, and you know, ultimately this
Speaker 2: gate is getting high. We just don't know, But you
Speaker 2: might wonder about humans getting high, because, of course, both
Speaker 2: of these substances we mentioned, including psilocybin, of course, are
Speaker 2: known for their effects in human beings. So you might wonder, well,
Speaker 2: could not a human just come along and eat a
Speaker 2: bunch of cathanone or psilocybin infected cicadas and then experience
Speaker 2: that the intended high. And we have to remember that
Speaker 2: cicadas themselves have long been on the menu for humans,
Speaker 2: so there's nothing out of bounds about eating cicadas, But
Speaker 2: what about these infected ones? Could you get high?
Speaker 3: Okay?
Speaker 2: Well, fortunately, there have been some papers that have already
Speaker 2: analyzed this question. We've had some experts weigh in on it.
Speaker 2: So one individual, there's a doctor David Shelter aka bug
Speaker 2: Doctor Dave or bug Doc Dave from Ohio State University,
Speaker 2: and he's already taken to the news cycle to get
Speaker 2: ahead of this informing everyone that, okay, first of all,
Speaker 2: one hundred to one hundred and fifty pound human being
Speaker 2: would have to eat about one hundred infected cicadas to
Speaker 2: feel anything off of that cathinone in their systems. And
Speaker 2: if you weigh more than that, if you weigh more
Speaker 2: than one fifty, you're going to have to eat even
Speaker 2: more infected cicadas.
Speaker 3: You know, far be it from me to demonize into myphaji.
Speaker 3: Nothing wrong with eating insects, But I don't know if
Speaker 3: you ate that many infected cicadas, I feel like you
Speaker 3: might just barf before you got to got to the same.
Speaker 3: I don't know, well, I don't even know what the
Speaker 3: exact effects of cathinone are supposed to be in a human.
Speaker 3: Would it be similar to other common stimulants like caffeine
Speaker 3: or something.
Speaker 2: I was reading a little bit about other uses of it,
Speaker 2: and there are other ways that humans have long acquired it.
Speaker 2: It would be like a stimulant high. So that's another
Speaker 2: thing worth keeping in mind. It's like there are other
Speaker 2: ways out there to get this other than eating cicadas.
Speaker 2: And I also have seen it advise that when humans
Speaker 2: do eat cicadas, we tend to eat the ones that
Speaker 2: have just emerged from their shells, like these are the tastiest.
Speaker 2: These are the juiciest. I've heard them described as buttery.
Speaker 2: The ones we're talking about the ones that are full
Speaker 2: of pathoogenic fungal spores. These look like they would even
Speaker 2: if you're not talking about eating a big lump of
Speaker 2: fungal spores, they're going to be like maybe crustier and
Speaker 2: crunchier and like just not as good.
Speaker 3: Yeah. So so the ones that have just emerged, they're
Speaker 3: like the soft shell crabs of the insect world.
Speaker 2: Yeah, I think that's that's that's probably an accurate comparison. Like,
Speaker 2: you want the soft shell It's okay this, you don't
Speaker 2: want the drier ones, the older ones, And that's not
Speaker 2: even counting in this big old lump of spores. And
Speaker 2: I also found some additional info in this. Matt Cassen,
Speaker 2: an associate professor of forest pathology and mycology at West
Speaker 2: Virginia University, points out in a Carol Murphy Marcos article
Speaker 2: for The Guardian that, Okay, we do have people out
Speaker 2: there already trying this, trying to eat a bunch of
Speaker 2: cicadas to get that stimulant hit. But he cautions again
Speaker 2: he says, quote, there's always a risk in eating cicadas
Speaker 2: pump filled with amphetamines. That was just one of a
Speaker 2: thousand compounds we found in the cicadas, and we don't
Speaker 2: know what those other compounds are capable of doing to humans.
Speaker 2: So I think all that sounds like a good reason
Speaker 2: to maybe pass on this particular high if you ask me,
Speaker 2: I mean, it's not going to make your butt crumble
Speaker 2: or anything. I mean, nobody's arguing that like these are.
Speaker 2: You know, like others have pointed out in some of
Speaker 2: these articles, you can pick up one of these infected
Speaker 2: cicadas and look at it. You might want to wash
Speaker 2: your hands afterwards, but it's not like, oh, I might
Speaker 2: catch these spores like these are these spores are not
Speaker 2: for you. But on the other hand, I don't eat
Speaker 2: a hundred of them because I just aren't exactly sure
Speaker 2: what else is in there. Yeah, So in general, there's
Speaker 2: a better use of your time. There are better ways
Speaker 2: to enjoy the cicadas, you know, listen to them, enjoy
Speaker 2: the ambiance, or in decide that this is essentially the
Speaker 2: muse is telling you you need to get deep and
Speaker 2: talk about philosophy. I guess the other challenge worth pointing
Speaker 2: out here is, of course, again in general, we're talking
Speaker 2: something like five percent of the cicada population, So you're
Speaker 2: gonna have, you would have to do a fair amount
Speaker 2: of foraging to get anywhere anything like enough dead cicadas
Speaker 2: to eat for this particular ill advised experiment, I'd say
Speaker 2: have an espresso instead.
Speaker 3: Did you find it? I wonder what do the natural
Speaker 3: predators think about the infected ones, so they have any
Speaker 3: preference for against do they care?
Speaker 2: You know, I didn't see that address in any of
Speaker 2: the articles I was looking at. Yeah, you are predators
Speaker 2: avoiding the infected cicadas that maybe something will have to
Speaker 2: come back to if there's anything out there dealing with it.
Speaker 3: Well, I asked, because I'm again not recommending people eat
Speaker 3: these things for the aforementioned reasons, But you know, I
Speaker 3: think about there are cases of certain certain things with
Speaker 3: fungal infections being considered especially good or a delicacy, at
Speaker 3: least by humans, and in some cases maybe preferred by
Speaker 3: some predatory animals. I think about like you know, wheedlcoche
Speaker 3: in maize and stuff like that.
Speaker 2: Yeah, yeah, or certainly you could. This is not a
Speaker 2: one to one here, but you could talk about the
Speaker 2: fermented fruit being attractive to various mammal species. You know,
Speaker 2: It's like when food when prey undergo certain changes, it
Speaker 2: may be more desirable. So yeah, I'll have to look
Speaker 2: around a bit more and see if anyone's talking about this,
Speaker 2: but I did not, and at least initially come across
Speaker 2: a study that tackled it well.
Speaker 3: Before we wrap up, there's one more thing I wanted
Speaker 3: to bring up today because I mentioned it in the
Speaker 3: last episode. Was and it was the idea of other
Speaker 3: possible explanations for why periodical cicadas would have these long
Speaker 3: thirteen and seventeen year periods between synchronized emergencies, like what
Speaker 3: are the evolutionary pressures driving that, apart from the hype
Speaker 3: athesis that it that it's part of a kind of
Speaker 3: beefing up of the satiation strategy, the anti predator strategy,
Speaker 3: which does seem to be a dominant way of thinking
Speaker 3: about it. But there are questions about that kind of strategy.
Speaker 3: And one is, for example, only a few species of
Speaker 3: the many many species of cicadas on Earth are periodical
Speaker 3: like this, And if it is, and you know, all
Speaker 3: these other annual cicadas from around the world are also
Speaker 3: preyed on by you know, lots of predators eat them,
Speaker 3: and so if this is such a a such a
Speaker 3: fruitful strategy, why don't more species exhibit it.
Speaker 2: Yeah, that's a great point. And it also it didn't
Speaker 2: run across any speculation on this in the in the past,
Speaker 2: but we talked about how the mergence of periodical cicadas
Speaker 2: in North America is relatively speaking, a recent occurrence, a
Speaker 2: recent development. It does make one wonder have there been
Speaker 2: other cases in the history of insects on Earth where
Speaker 2: some sort of insects species or another adapted to some
Speaker 2: sort of periodical lifestyle life cycle and it has just
Speaker 2: fallen away over time either those species went extinct, you know,
Speaker 2: or they evolved into stages they had to essentially become
Speaker 2: annual again, or something to that effect.
Speaker 3: Yeah, yeah, I don't know. But I was looking into
Speaker 3: this question of like, Okay, well, what would other explanations
Speaker 3: be if it's not just this anti predator strategy or
Speaker 3: way to avoid parasitoids or predators adapting to your emergen cycle.
Speaker 3: And there seemed to be a few ideas floating around
Speaker 3: out there. One general class of explanations is that it
Speaker 3: is somehow just sort of a remnant of an adaptation
Speaker 3: that was formed during the Pleistocene epoch. During there was
Speaker 3: a lot more glaciation in North America, and that these
Speaker 3: periods of cold unstable weather would move further and further south,
Speaker 3: and this pressure, the pressure of unpredictable cold weather, caused
Speaker 3: some cicadas to extend their underground periods and it provided
Speaker 3: an evolutionary incentive. It rewarded them from coming out less often,
Speaker 3: developing these longer and longer periods underground, and then from
Speaker 3: that point on it was of course useful for these
Speaker 3: species to synchronize their emergencies to all come out at
Speaker 3: the same time. There was an incentive in favor of that.
Speaker 3: Another hypothesis I've seen for specifically the thirteen and seventeen
Speaker 3: year timing of the emergencies is that once there were
Speaker 3: ancestral periodical populations in place, there would have been a
Speaker 3: biological incentive to avoid breeding with other populations that had
Speaker 3: a differently timed cycle, because this could lead to hybridization,
Speaker 3: which would interfere with the periodicity adaptation. So like, in
Speaker 3: order to be effective as a periodically emerging species, you
Speaker 3: really want to be fully synchronized, like have all your
Speaker 3: population come out at once within the same place, so
Speaker 3: that you can take best advantage of predator satiation and
Speaker 3: so forth, and so it's possible there's a disincentive for
Speaker 3: thirteen and seventeen year populations to interbreed because that might
Speaker 3: unsynchronize them. But I've also seen arguments sort of coming
Speaker 3: back against that, so it seems like to some extent,
Speaker 3: I think we alluded to this in the first episode.
Speaker 3: It still somewhat remains mysterious exactly why these thirteen and
Speaker 3: seventeen year time scales have been selected by evolution, but
Speaker 3: still leading hypotheses have something to do often with predator satiation.
Speaker 3: Either it's too as we've said, to avoid predator and
Speaker 3: parasitoid adaptations matching the times of the emergence, or to
Speaker 3: avoid interbreeding or to h or maybe it is related
Speaker 3: to patterns that emerge during the ice age and have
Speaker 3: stuck around ever since.
Speaker 2: Fascinating though anyway you look at it, and it's just
Speaker 2: one of the I think the great things about cicada
Speaker 2: is there's just so many interesting layers to them, from
Speaker 2: their their their basic anatomy and basic physiology, to these cycles,
Speaker 2: to then human interpretations of these cycles. Uh yeah, so
Speaker 2: much fun. And I guess we might be pressing on
Speaker 2: with another episode. I don't know, it's kind of TBD
Speaker 2: at this point. Will there be a Cicada Part four
Speaker 2: in this series? We're gonna have to to go back
Speaker 2: to the notes and take a look. But I guess
Speaker 2: you know you'll find out in a couple of days.
Speaker 3: Here see what emerges on Thursday.
Speaker 2: That's right, all right, We're gonna goe and close out
Speaker 2: this episode, but hey, you have Cicada thoughts, Cicada observations
Speaker 2: right in. We would love to hear from you. Now
Speaker 2: that I think about it, I think we had a
Speaker 2: listener right in out the Bearside angle and nudged us
Speaker 2: forward on that, So you know, I don't recall who
Speaker 2: wrote in with that, but certainly that helped nudge us
Speaker 2: in this direction. But yeah, right in, we'd love to
Speaker 2: hear from you. And just a reminder that Stuff to
Speaker 2: Blow your Mind is primarily a science and culture podcast,
Speaker 2: with core episodes on Tuesdays and Thursdays. On Mondays we
Speaker 2: do listener mail. Wednesdays, there's generally a short form episode,
Speaker 2: and then on Fridays we set aside most serious concerns
Speaker 2: to just talk about a weird film on Weird House Cinema.
Speaker 3: Huge thanks as always to our excellent audio producer JJ Posway.
Speaker 3: If you'd like to get in touch with us with
Speaker 3: feedback on this episode or any other, to suggest a
Speaker 3: topic for the future, or just to say hello, you
Speaker 3: can email us at contact at stuff to Blow your
Speaker 3: Mind dot com.
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