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June 25, 2024 46 mins

In this episode of Stuff to Blow Your Mind, Rob and Joe explore the world of the periodical cicada, from their curious lifecycle to their mythological and culinary roles in human cultures. 

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Speaker 1 (00:03):
Welcome to Stuff to Blow Your Mind production of iHeartRadio.

Speaker 2 (00:12):
Hey you welcome to Stuff to Blow Your Mind. My
name is Robert Lamb.

Speaker 3 (00:16):
And I'm Joe McCormack, and we're back with Part three
of our series on cicadas. Now, if you haven't heard
the first two parts yet, you probably want to go
check those out first. This is one where we lay
a lot of the groundwork in the earlier episodes. This
series was a little strange because we broke right in
the middle of it after part one for a break
that we had for a couple of weeks, came back

(00:37):
last week with Part two, and here we are with
Part three.

Speaker 2 (00:40):
Now.

Speaker 3 (00:40):
In Part one, we talked about the basics of cicada biology,
their branch of the insect family tree, their life cycle, reproduction,
the sounds they make, their bodies and organs, and the
evolution of long underground developmental periods and timed emergences in
the minority of SCA, a species known as periodical cicadas,

(01:02):
which we have here in North America. We just had
a very interesting and rare kind of coinciding emergence of
two relevant broods of thirteen and seventeen year cicadas this
year in twenty twenty four. The last time this coinciding
emergence happened was like two hundred and twenty one years ago,
so that's pretty cool. In part two of the series,

(01:26):
we talked about the history of people being concerned with
the question of whether periodical cicadas will bite them or
sting them, or stuck out all their blood and leave
them a thoroughly pumped frame. In the words of one
New York Times article from the nineteenth century, they won't
do that. Don't worry, it's not going to happen. And
then we talked about the work of the American entomologist

(01:47):
Charles Lester Marlott, who did important research mapping and cataloging
the different broods of periodical cicadas in eastern North America.
And today we're back to talk about more cicada stuff
right now.

Speaker 2 (02:01):
Later on in this episode, we are going to be
talking about a rather unique and by many standards, gnarly
parasite of periodical cicadas, one that you may already be
familiar with, even if it's like just surface level, because
it's a rather outrageous example that sometimes breaks the surface
of even late night coverage of science news. But before

(02:24):
we're going to do that, we have a little cicada mythology,
a little general cicada history to jump into here, right right.

Speaker 3 (02:31):
So I came across an interesting fact, which is that
cicadas are featured in one of Plato's dialogues, one that
I've read before, and I had no memory of this
being a part of the discussion at all. And this
dialogue includes a mythological origin story for cicadas. So the

(02:51):
dialogue in question is Plato's dialogue The Feedress, and it's
a story told by Socrates. So Fedris is a very
famous dialogue of Plato. A lot of people read it
in school. It covers a wide range of topics art, love, madness, reason, rhetoric, etc.

(03:11):
It's the source of that famous chariot analogy where Socrates
describes the soul as a chariot pulled by two horses
with very different temperaments, each representing different forms of passion
and instinct within human nature. And then the charioteer is
sort of the reasoning part of the soul that must
tame the two horses and steer them together on the

(03:33):
path of truth and righteousness. Even though they want to
go in different directions on their own. But anyway, the
story of the cicadas is not part of the Chariot analogy.
It comes partially due to the setting of the dialogue.
So in this dialogue, Socrates and this other guy, Feedris
are outside the city of Athens, and it is said

(03:54):
that they're sitting on the banks of a stream having
a good old philosophical conversation, and in the background cicadas
are singing. They make reference to this a couple of
times in the dialogue, and then Socrates starts imagining that
if he and Fedris were not doing what they're doing,
not having a philosophical conversation, but we're instead just lying

(04:16):
by the river listening to the cicada song, he says
that the cicadas would have a right to laugh at
them for being lazy and unvirtuous. But since the cicadas
know that Socrates and Fedris are instead discoursing on philosophy,
trying to get to the truth, and not being just
lulled to sleep by their song, he says quote, they

(04:39):
may perhaps, out of respect, give us of the gifts
which they receive from the gods, that they may impart
them to men, And then Fedris says, what gifts are
you talking about? What gifts to cicadas have to give
two men from the gods? And here I'm going to
read socrates response. This is the Benjamin Joet translation orig

(05:00):
generally renders the name of the insect here as grasshoppers.
But it seems to me generally agreed that this story
is referring to cicadas. So I've gone through the passage
and replace the word grasshopper with cicada. Excellent, Socrates says,
A lover of music like yourself ought surely to have
heard the story of the cicadas, who are said to

(05:20):
have been human beings in an age before the muses.
And when the muses came and song appeared, they were
ravished with delight and singing, always never thought of eating
and drinking, until at last, in their forgetfulness, they died.
And now they live again in the cicadas. And this

(05:42):
is the return which the Muses make to them. They
neither hunger nor thirst, but from the hour of their
birth are always singing and never eating or drinking. And
when they die, they go and inform the Muses in heaven,
who honors them on earth. They win the love of
terpsickery for the dancers by their report of them, of

(06:02):
Erato by the lovers, and of the other muses, for
those who do them honor according to the several ways
of honoring them, of Calliope, the eldest muse, and of Urania,
who is next to her, for the philosophers, of whose
music the cicadas make report to them. For these are
the muses who are chiefly concerned with heaven and thought

(06:23):
divine as well as human, and they have the sweetest
utterance for many reasons. Then we ought always to talk
and not to sleep at mid day. So cicadas, according
to this story, were humans before the time the muses
came into being. And when the muses came to exist,
they brought with them music. They brought song, and then

(06:45):
the pre muse humans were so enraptured by the invention
of music that they entertained themselves to death. They listened
to music without eating or drinking until they just died.
And I guess made me to made music. Listen to music,
it's all song and dance, until they just straight up died.

Speaker 2 (07:04):
This is why you have concessions.

Speaker 3 (07:05):
Yeah, exactly right, Yeah, but then but then the muses
allow them to live again as cicadas and to sort
of to be snitches for the muses, you know, to
be the muse's earthly surveillance team, to kind of like
hang out down here and spy on people and see
who's honoring the muses properly and who is not honoring them.

(07:27):
And I was thinking about this and how it seems
like it's kind of interesting to me to see how
norms of moral and intellectual virtue are kind of different
in our culture versus what Socrates is proposing here, because
it seems like Socrates is talking like it's just rather
obvious that sitting silently in nature, maybe falling asleep by

(07:49):
a river, listening to the insects vocalized, is something akin
to a vice. At the very least. It's like intellectually
lazy and not worthy behavior in the view of the
intellectual muses like Calliope and Urania, who are muses of
things like philosophy and eloquence and astronomy and stuff, you know,
the muses of learning. And it's thought that these muses

(08:14):
would certainly see it as better for people to be
engaged in philosophical argumentation. And this is to the extent
that in the comment right before this selection, when Socrates
is talking about, like, you know, he's first talking about
the cicadas looking at them and judging what they're doing.
Socrates says, quote, but if they see us discoursing like Odysseus,

(08:35):
sailing past them, deaf to their siren voices, they may, perhaps,
out of respect, give us of the gifts which they
receive from the gods, that they may impart them to
men okes. I read the last part of that.

Speaker 2 (08:49):
Yeah, all right, So the cicadas are singing, they're busy,
enraptured by song, and if we're not living our lives
to like full creative musical extent that we could, then
they are going to shame us, and they're going to
laugh at us. But if we're busy talking, having philosophical discussions,

(09:12):
then they might just give us a little gift here
and there.

Speaker 3 (09:15):
Right, they'll go tell the muses that we've been good.

Speaker 2 (09:17):
Yeah, we'll get a boon, Okay, okay.

Speaker 3 (09:20):
But it's interesting that kind of difference in expectations because
I think among I don't know, probably a lot of
people sitting listening to this podcast right now, a lot
of us today, I think probably think that sitting quietly
in nature and listening to the bugs, sitting by a river,
maybe dozing off is an activity that would be more
associated with like virtue and seriousness and discipline and so forth,

(09:43):
things like that today, And I don't think that would
be widely seen as like a less intellectually serious type
of activity than arguing about the nature of reality and
a philosophical discourse. It seems like, you know, every yahoo
an out there wants to argue about what's true. You know.

Speaker 2 (10:00):
Yeah, you can imagine like Socrates busting into my new
yoga class that I go to and saying, why aren't
you talking about philosophy? What are you doing laying about
doing stretches, being in the now? Stop it?

Speaker 3 (10:13):
So, I don't know, maybe our norms today extend from
the idea that like, there are access to easier entertainments
than like listening to the cicadas or something, and so
if you're like really intellectually lazy, you're like watching TV
or something instead of, maybe to the ancient Greek sitting
and listening to the cicadas and dozing off by the river.
That's the equivalent of watching TV or something.

Speaker 2 (10:35):
I don't know, Yeah, I mean it also sounds like
he's kind of shaming folks for being inactive and resting
a little bit during like the hottest part of the day,
you know. So I don't know, but I think you're right. Yeah,
this does kind of turn a lot of our modern
ideals and aspirations about everything from I mean really everything

(10:56):
from midday rest and you know the idea of taking
the siesta to doing like a mid day exercise, mid
day yoga, meditation, or even just a mid afternoon nap. Yeah.

Speaker 3 (11:07):
But I also like the idea that this mythology of
cicada origins incorporates a couple of things. I mean, one
is the interesting, like you know, the entertain themselves to
death concept. It's not unique like that. There are other
stories of similar kind of people who get so excited
by some kind of activity that they forget to live.
And so there's that aspect. But also I like the

(11:27):
idea of cicadas as surveillance devices, that they are down
here spying on us for the gods, because it can
sort of feel like that, right, like the way that
you go into their space and you can't see them,
but you imagine they can see you. It often feels
this way with various kinds of bugs that make sounds

(11:49):
in the night, whether it's cicadas or not, because you
might have that experience of, say, going into the woods
at night and there bugs making sound, But then the
bugs get quiet, so you realize they're aware of your
presence and reacting to it, but you can't see any
of them. So it does feel like a kind of
surveillance situation.

Speaker 2 (12:08):
Yeah. Yeah, you're literally bugged right, Oh yeah, yeah, And
there is like we've been discussing with the cicadas like that,
just that feel of them in their masses, like the
rise and fall of their cadence. It it does have
this very surreal feel to it. It feels like, like
I say, I often think about it as just being

(12:29):
like part of the midday heat. You know. It's it's
something that's difficult for the human mind to sort of
fathom as what it is, like, all these individual cicadas
making little sounds. It feels like something much bigger than
us in many ways.

Speaker 3 (12:44):
Yeah, almost like the gods are in on it. Yeah.
But if there are some aspects of cicada biology that
might make them feel like an envoy of the muses
or some kind of you know, allied with the heavens.
There are other ways in which you can learn things
about cicadas that really make them like they were cursed
by the devils, like if Hades has it out for them, Yeah.

Speaker 2 (13:05):
Yeah, yeah, cursed by the gods or you know, who
are we to question the strange creations the lonely perfection
of the gods. I want to talk a bit about

(13:25):
one very notable parasite of cicadas in general, but there's
a lot of emphasis on the varieties that target are
periodical cicadas. So we've already discussed the unique life cycle
of the periodical cicadas and some of the ideas concerning
why they spend thirteen or seventeen years underground in this

(13:49):
low metabolism subterranean larval form and then eventually erupt and
engage in this noisy litter, producing a feast for predators
but also very vital reproductive cycle of their lives. And
one of those one of the ideas behind this is

(14:10):
that they do this in order to outmaneuver various predators
and parasites that otherwise might sync up with their life cycle.
Now We've already admitted though that this may seem to
work in some cases, but periodical cicadas have not been
able to outmaneuver everything. And of course we also discussed

(14:30):
how like, basically the idea of everyone emerging at once
and reproducing also is to just overwhelm predators. They can't
possibly eat everything, and any given species are going to
live in some degree of equilibrium with its parasites, with
its predators and so forth.

Speaker 3 (14:46):
This actually would be a good place to mention something
interesting I came across in research since the last episode,
which is I was looking for more information about the
actual direct evidence for predator saciation in periodicals, and again,
satiation is the evolutionary strategy we've been talking about. It's
one hypothesized reason for these mass periodical emergencies, where the

(15:10):
idea is, again there are more cicadas than all the
predators that eat them can possibly eat all at the
same time, So the eating capacity of the predators and
also the parasitizing capacity of the parasitoids is overwhelmed. There's
too much all at once, and thus each individual cicada's
chances of suffering from predation are much lower. So I

(15:33):
was like, well, what is the actual evidence for predator saciation,
and so I found an interesting study. It was won
by Richard Carbond done in the journal Ecology in nineteen
eighty two called Increased reproductive success at high densities and
predator satiation for periodical Cicadas. In the study, the researchers
combed over selected areas during periodical cicada emergencies and collected

(15:57):
cicada wings, which was an interesting strategy. Basically, they were
trying to look at bird predation on cicadas and they
discovered that wings are often discarded when birds eat cicadas,
so bird chomps the cicada, the wings fall off, and
so they collected wings in these areas to allow the

(16:17):
researchers to form rough estimates of how many cicadas are
eaten by birds within the area at a given time period.
And what the author here found was interesting. The number
of wings increased its sites with more bird density, so
cram more predators into a region, more cicadas get eaten,
but the number of wings did not increase at sites

(16:39):
with more cicada density, so more things to eat doesn't matter.
Nothing more gets eaten. In other words, if you put
more cicadas in the area, and the bird population remains
the same. No additional cicadas get eaten by birds, because
the birds are already eating their fill. There's already more
than they possibly can get to, and thus each end

(16:59):
of jual cicada's chance of being eaten goes down. That's
the predator satiation scenario. The predators are full. But of
course the real danger in the bird predation scenario would
be if the birds caught on to this in some
way and increased their numbers to take advantage of this
massive amount of leftovers. Maybe if they had more offspring

(17:21):
and increase their population density at the time when cicadas
were available, or if more birds migrated to the area
at the time when cicadas were available, or something like that.
So if the number of predators goes up, the safety
advantage for cicadas goes down. And this is another reason
that it's hypothesized that the thirteen or seventeen year period

(17:44):
is helpful. The ideas this makes it harder to track with,
like the predators can't sync up their migration or reproductive
or whatever cycles to be in the right place at
the right time to take advantage of all the cicada biomass.
So sorry for the digression, but I had discarded cicada
wings on the brain, So that'll bring us back to

(18:05):
you were saying that the cicadas are not able to
outmaneuver everything, and there's one organism in particular that is
a parasite that has adapted to periodical cicadas.

Speaker 2 (18:16):
That's right. This organism is Masospora cicadia. And this is
a fungal pathogen that was discovered by American mycologist and
botanist Charles Horton Peck back in eighteen seventy nine, who
is a pretty important figure in North American mycology around
the turn of the twentieth century. I think like thousands

(18:36):
of different species of fungus were described by him, North
American fungo, fung gui and he was also the New
York State Botanist from eighteen sixty seven through nineteen fifteen.
So I went back and I was reading Peck's original
report on the fungus in question, back in eighteen seventy
nine's thirty first Annual report on the New York State

(18:58):
Museum of Natural History by the Regions of the University
of the state of New York.

Speaker 3 (19:03):
What state was that in?

Speaker 2 (19:05):
Well, New York, of course. But the paper is quite readable,
and it describes most of the key features of the
parasitic infection of periodical cicadas, and does so redis succinctly.
So I'm going to read a passage from it here.
But basically he starts off by mentioning that fungal parasites
of insects are known and are quite common. So this was,

(19:29):
in and of itself nothing new. And certainly, if you
pay any attention to science news, you have run across
various examples of those various fungal parasites that depend on insects,
and in many cases, like you don't seem to alter
their biology and or behavior. You know, puppet masters if
you will.

Speaker 3 (19:49):
Yeah, we've done episodes in the past about Ohiocordyceps fungus
specifically praying on insects, and I don't know if this
has overlapped with that or not, but.

Speaker 2 (19:58):
There are some I think it it lines up in
places though there are some mysteries that remain, and I
think there's still you know, there's still certain mysteries that
remain with with other examples of fungal parasites. We're still
learning a lot. There's still some things that are more
in the realm of hypothesis that sometimes maybe get picked
up and carried into the mainstream press a little more

(20:19):
settled than they actually are. We're still learning a lot.
At the time of this writing, though, this was a
new one and it was based on some specimens that
had been sent to Peck from New Jersey. So in
this text he writes, the fungus develops itself in the
abdomen of the insect and consists almost wholly of a
mass of pale, yellowish or clay colored spores, which to

(20:42):
the naked eye has the appearance of a lump of
whitish clay. The insects attacked by it becomes sluggish and
averse to flight, so that they can easily be taken
by hand. After a time, some of the posterior rings
of the abdomen fall away, revealing the fungus within. Strange
as it may seem, the insect may and sometimes does

(21:03):
live for a time even in this condition. So that's
some of like the basic observable aspects of this. And
I don't believe I've ever looked at a cicada specimen
with this scenario. I mean, I've you know, in the
course of my life, I've I've nudged quite a few
with my feet, you know, or or accidentally stepped on one.
But I don't know if I've noticed this before. But basically,

(21:24):
if you look at the pictures and footage and so forth,
you will find adult cicada specimens, so winged specimens that
have they have a situation where their abdomen has seemingly
like turned to like chalky clay. You know, It's almost
like their abdomen has internally petrified and then begins to crumble,

(21:46):
with the outer ridges falling away from it.

Speaker 3 (21:48):
And yet the insect is at this point still alive,
which is gross and weird to think about, right.

Speaker 2 (21:55):
Yeah, yeah, And as as Pack pointed out, you know,
there are many observ do say that they seem to
be more sluggish. I'll get into a little bit about
that in a bit. But then on the other hand,
they can also seem very energetic. So there's a lot
going on here. And again there seems to be a
lot of investigation still ongoing in various hypotheses regarding exactly

(22:16):
what's going on, and then there's certain things that are
just unknowable. You know, we cannot know the mind of
the cicada.

Speaker 3 (22:22):
Yeah, it's just hard to imagine, like a mammal equivalent,
Like if a human, like the low from your belly
button down, that like is just gone, that fell off,
and there's just like a big lump of white clay
chalk kind of gunk sticking out of the bottom of
your torso and you're still alive and moving around, but
maybe sluggish.

Speaker 2 (22:39):
Yeah, yeah, leaving a trail of spores behind you and
occasionally rubbing spores against other humans and infecting them. So
I looked to a couple of different recent sources about
the organism in question. Rachel treisman Over at MPR covered
M Cicadina earlier this month, providing a nice overview of

(23:00):
the organism. Essentially, it's still quite active and one of
the reasons, of course, you know, we have these emergencies,
these these two major broods, and so there are a
lot of periodical cilicadas out there, and there's gonna be
a certain amount of infected periodical circados to check out.
So I'm gonna have to keep an eye open for

(23:21):
these now. And certainly listeners write in if you find one.
But it's interesting that the chalky abdomen that we've been
describing it does kind of match up with the name
of the organism. So massospora essentially means spore grinder, alluding
to the fact that it would almost seem that the
hind parts of the cicada have been again petrified and

(23:42):
then pulverized or like grated, you know, like parmesan cheese
or something.

Speaker 3 (23:48):
Oh not the not the shreds, but the dust. Yeah,
using that side of the greater box. Yeah, you want
the dusting, right, Yeah. So it's try some points out here. M.
Cicadina employees is active host transmission, So the cicada again
remains alive and active, though its behavior may be altered
by the fungus, or i mean, the behavior seems to

(24:09):
be altered by the fungus. Exactly how it's being altered,
you know, if we're talking physically, chemically, so forth. There's
a lot of back and forth over that. But all
of this does seem to serve to optimize the distribution
of the spores. So let's break down the live cycle.
And I'm also drawing on a specialized fungal parasite hijacks

(24:30):
the Sexual Signals of periodical Cicadas by koli at All,
published in scientific reports back in twenty eighteen. Okay, so
remember the life cycle of the periodical cicada. So it
begins here with the emergence of those periodical cicadas. They're
coming up through the ground and as this occurs, some
of the individuals become infected with this this fungal parasite. Now,

(24:56):
the exact number, estimates are maybe five percent of the
population total according to Treisman, but the number can reach
twenty to thirty percent in different areas. So you know,
you might have a like a major hub, a major
area where they're the higher.

Speaker 2 (25:11):
Rate of infection. But overall it's thought that maybe this
is like five percent of the periodical cicada population. Okay,
so these are already these ones that are emerging and
become infected as they emerge. More than that at a second.
In a second, these are stage one infected cicadas, and
they produce haploid condiospores that can infect other active adult cicadas.

(25:37):
Later on in the emergence, the cicadas infected by these
spores becomes stage two cicadas and stage two infected cicadas,
and they produce diploid resting spores. These spores fall to
the ground where they can actually seemingly lay dormant in
or on the soil for thirteen to seventeen years, though

(25:57):
they can activate pretty much right away, but they're there
on or in the soil, and they infect emerging nymphs.

Speaker 3 (26:06):
Ah okay, So spores that can just lie in wait
for thirteen or seventeen years get around the periodical adaptation
in a way that the population of predatory animals could not.
You can't have a big enough population of birds to
eat all of the cicadas just waiting around for thirteen
years for them to come back. They'd starve in the meantime.
But if you're a spore, you can just sit there

(26:27):
and wait.

Speaker 2 (26:28):
That's right, like a little landmine, ready to go off
and infect one of those nymphs when it begins emerging
for the final period of the life cycle. So that's
the basic cycle. But then there are the details of
what the infection does. The major thing, of course, is
what we've already talked about. This is the distension and

(26:51):
loss of these abdominal segments, which includes the genitalia in
both sexes, So, in other words, turns the entire inside
of the abdomen into one big mass of spores, it
loses any of its reproductive organs, and then all of
this becomes exposed as the outer abdomen eventually ruptures and

(27:12):
begins to fall away, and they turn into crawling, flying
spore crop dusters.

Speaker 3 (27:18):
So they're just crawling around great in the spiky side
of the box grade or just dusting everything.

Speaker 2 (27:24):
That's right, that's right. And this is where the topic
of behavioral adaptation comes into play. To what degree is
the parasite also manipulating behavior of the infected cicada. So yeah,
a lot of coverage points to this, but when you
get into some of the papers, such as the one
I just cited, there seems to be a lot more
uncertainty because, on one hands, cooly I all point out

(27:45):
some of the apparent changes in behavior may be brought
on as much by physical changes due to the infection.
For instance, they cite that infected cicadas often remain more stationary,
make shorter flights, and drag their abdomens when they want
trailing spores. Of course, and these changes could in large
part be brought on by the damage they've sustained via

(28:06):
the infection. Again, they've they've they've sustained a lot of
damage here. They're they're abdomen has been transformed into just
a sport a crumbling spor sack with the flesh, you know,
crumbling off around it. And they also point out that
stage ones tend to walk and trail more, while Stage
twos tend to fly and spread. So, you know, I

(28:26):
guess the idea here is Stage ones are trailing and
around in you know, on branches and areas where other
cicadas are going to gather, while the stage twos they're
flying around because their spores are you know, mint if
we we dare use that word to to to fall
to the ground where they will be useful later on
when nymphs emerge. But they stressed that this could be

(28:49):
behavioral manipulation as well. Uh So, here's where it gets
even more interesting. This, according to Coolie at All quote,
stage one massive spora infection, which produce spores that are
spread directly to other adult cicadas, cause males to wingflick
in response to the calls of other males with the
same species specific timing used by sexually receptive magicicada females.

(29:15):
These novel wing flick responses are attractive to normal, uninfected
males who repeatedly attempt to copulate with the disease males.
So these copulations are going to be unfruitful, be it
male female or male male matches, because remember the genitals
are all destroyed anyway. But it results in a mimicry

(29:37):
of receptive mates, and so they end up, you know,
rubbing their abdomens together. At least, you know, you're getting
those spores moved around, the scores spread, and that, at
least to the fungus is what matters. And in this
the fungal pathogen acts as a sexually transmitted pathogen.

Speaker 3 (29:55):
Okay, so this is an example of how it may
be the fungus, as we've seen in other examples of
a fungi that infect insects. Because remember, like the other
example I mentioned the Ohio Cordyceps fungus which infects ants.
I think that's the one that causes them to you know,
it makes them like climb up to the top of
a you know, some overhanging thing, and they like glatch

(30:18):
onto it, and then they grow these bodies out of
like a spike out of their head or somewhere out
of their bodies and rain down spores on the other
ants below. That's an example of what is thought to
be a kind of behavior manipulation, and this looks more
like a direct behavior manipulation, and not just the insects
responding to changes in their body right.

Speaker 2 (30:38):
But with one potential caveat when we get to the
chemical aspect of what may or may not be going on. Okay, okay,
so okay, So we have these stage ones, We have
these males on their branches, twitching their wings like their females,
attracting other males. Stage two infections, though, do not cause
this behavior. And again the stress seems to be on

(30:59):
these these stage two infected cicadas spreading these spores to
the ground where they will in time infect emergent nymphs.
So this is where we get to the chemical aspect
of it, and the idea that there's chemical manipulation going

(31:22):
on as well by the parasite. So as pointed out
in Triisman's article, the fungus has also been found to
produce a stimulant called cathinone a plant associated amphetamine in
four infected cicada populations, and then elsewhere we have infected
populations of annual cicadas which were found to contain the

(31:44):
hallucinogen psilocybin, according to a study published in Fungal Ecology
back in twenty nineteen.

Speaker 3 (31:50):
Wait a minute, so it's this fungus is getting its
hosts sort of caffeinated and on mushrooms.

Speaker 2 (31:59):
Essentially, Yeah, there is. So one of the big caveats
here is that, again, we can't know the mind of
a cicada. Right, A lot of headlines that you know,
you know, at least jokingly have some fun with the
idea that the cicadas are high out of their minds.
We don't really know if they're high, but we can't help.
But but but look at these chemicals in these cicadas

(32:22):
and wonder, like, what the purpose is here? What is
it doing? And to what degree is it affecting behavior?
And there seems to be a strong case for.

Speaker 3 (32:31):
That, right, I apologize for over anthropomorphizing by implication.

Speaker 2 (32:35):
No no, no, no, But you're you're also onto the
right track too. So I couldn't find as much about
the psilossignment aspect and again, those are going to be
annual cicadas and not periodicals. But there has been more
hypothesized about the stimulants in the periodical cicadas, so some
have speculated that these do in fact enhance cicada libidah

(33:00):
or to some degree make this caya not particularly care
about the physical changes they're undergoing. But the other main
interpretation is that that that cathinone the stimulant is what
causes that rapid wing movement, So like, oh, like, why
are they moving their wings rapidly and mimic and ultimately
mimicking receptive females. It could be because they're just jacked

(33:22):
up on this uh, this this particular stimulant in their
bodies and it's causing the wing flapping, which then causes
this additional behavioral change.

Speaker 3 (33:32):
So it's possible the stimulant causes just sort of a
nervous behavior, like a flexing kind of behavior, which happens
to resemble mating signals, which attracts other males who hopefully
will get infected by this fungus from the fungus's perspective.

Speaker 2 (33:47):
That's right. Again, there's a lot there's a lot more
to consider there, and there seems to be a lot
of work still going on, and you know, ultimately this
gate is getting high. We just don't know, But you
might wonder about humans getting high, because, of course, both
of these substances we mentioned, including psilocybin, of course, are

(34:08):
known for their effects in human beings. So you might wonder, well,
could not a human just come along and eat a
bunch of cathanone or psilocybin infected cicadas and then experience
that the intended high. And we have to remember that
cicadas themselves have long been on the menu for humans,
so there's nothing out of bounds about eating cicadas, But

(34:30):
what about these infected ones? Could you get high?

Speaker 3 (34:34):
Okay?

Speaker 2 (34:35):
Well, fortunately, there have been some papers that have already
analyzed this question. We've had some experts weigh in on it.
So one individual, there's a doctor David Shelter aka bug
Doctor Dave or bug Doc Dave from Ohio State University,
and he's already taken to the news cycle to get
ahead of this informing everyone that, okay, first of all,

(34:57):
one hundred to one hundred and fifty pound human being
would have to eat about one hundred infected cicadas to
feel anything off of that cathinone in their systems. And
if you weigh more than that, if you weigh more
than one fifty, you're going to have to eat even
more infected cicadas.

Speaker 3 (35:11):
You know, far be it from me to demonize into myphaji.
Nothing wrong with eating insects, But I don't know if
you ate that many infected cicadas, I feel like you
might just barf before you got to got to the same.
I don't know, well, I don't even know what the
exact effects of cathinone are supposed to be in a human.
Would it be similar to other common stimulants like caffeine

(35:31):
or something.

Speaker 2 (35:32):
I was reading a little bit about other uses of it,
and there are other ways that humans have long acquired it.
It would be like a stimulant high. So that's another
thing worth keeping in mind. It's like there are other
ways out there to get this other than eating cicadas.
And I also have seen it advise that when humans

(35:52):
do eat cicadas, we tend to eat the ones that
have just emerged from their shells, like these are the tastiest.
These are the juiciest. I've heard them described as buttery.
The ones we're talking about the ones that are full
of pathoogenic fungal spores. These look like they would even
if you're not talking about eating a big lump of

(36:13):
fungal spores, they're going to be like maybe crustier and
crunchier and like just not as good.

Speaker 3 (36:18):
Yeah. So so the ones that have just emerged, they're
like the soft shell crabs of the insect world.

Speaker 2 (36:23):
Yeah, I think that's that's that's probably an accurate comparison. Like,
you want the soft shell It's okay this, you don't
want the drier ones, the older ones, And that's not
even counting in this big old lump of spores. And
I also found some additional info in this. Matt Cassen,
an associate professor of forest pathology and mycology at West

(36:46):
Virginia University, points out in a Carol Murphy Marcos article
for The Guardian that, Okay, we do have people out
there already trying this, trying to eat a bunch of
cicadas to get that stimulant hit. But he cautions again
he says, quote, there's always a risk in eating cicadas
pump filled with amphetamines. That was just one of a

(37:07):
thousand compounds we found in the cicadas, and we don't
know what those other compounds are capable of doing to humans.
So I think all that sounds like a good reason
to maybe pass on this particular high if you ask me,
I mean, it's not going to make your butt crumble
or anything. I mean, nobody's arguing that like these are.

(37:27):
You know, like others have pointed out in some of
these articles, you can pick up one of these infected
cicadas and look at it. You might want to wash
your hands afterwards, but it's not like, oh, I might
catch these spores like these are these spores are not
for you. But on the other hand, I don't eat
a hundred of them because I just aren't exactly sure

(37:48):
what else is in there. Yeah, So in general, there's
a better use of your time. There are better ways
to enjoy the cicadas, you know, listen to them, enjoy
the ambiance, or in decide that this is essentially the
muse is telling you you need to get deep and
talk about philosophy. I guess the other challenge worth pointing

(38:09):
out here is, of course, again in general, we're talking
something like five percent of the cicada population, So you're
gonna have, you would have to do a fair amount
of foraging to get anywhere anything like enough dead cicadas
to eat for this particular ill advised experiment, I'd say
have an espresso instead.

Speaker 3 (38:27):
Did you find it? I wonder what do the natural
predators think about the infected ones, so they have any
preference for against do they care?

Speaker 2 (38:35):
You know, I didn't see that address in any of
the articles I was looking at. Yeah, you are predators
avoiding the infected cicadas that maybe something will have to
come back to if there's anything out there dealing with it.

Speaker 3 (38:48):
Well, I asked, because I'm again not recommending people eat
these things for the aforementioned reasons, But you know, I
think about there are cases of certain certain things with
fungal infections being considered especially good or a delicacy, at
least by humans, and in some cases maybe preferred by
some predatory animals. I think about like you know, wheedlcoche

(39:11):
in maize and stuff like that.

Speaker 2 (39:14):
Yeah, yeah, or certainly you could. This is not a
one to one here, but you could talk about the
fermented fruit being attractive to various mammal species. You know,
It's like when food when prey undergo certain changes, it
may be more desirable. So yeah, I'll have to look
around a bit more and see if anyone's talking about this,
but I did not, and at least initially come across

(39:35):
a study that tackled it well.

Speaker 3 (39:37):
Before we wrap up, there's one more thing I wanted
to bring up today because I mentioned it in the
last episode. Was and it was the idea of other
possible explanations for why periodical cicadas would have these long
thirteen and seventeen year periods between synchronized emergencies, like what
are the evolutionary pressures driving that, apart from the hype

(40:00):
athesis that it that it's part of a kind of
beefing up of the satiation strategy, the anti predator strategy,
which does seem to be a dominant way of thinking
about it. But there are questions about that kind of strategy.
And one is, for example, only a few species of

(40:20):
the many many species of cicadas on Earth are periodical
like this, And if it is, and you know, all
these other annual cicadas from around the world are also
preyed on by you know, lots of predators eat them,
and so if this is such a a such a
fruitful strategy, why don't more species exhibit it.

Speaker 2 (40:40):
Yeah, that's a great point. And it also it didn't
run across any speculation on this in the in the past,
but we talked about how the mergence of periodical cicadas
in North America is relatively speaking, a recent occurrence, a
recent development. It does make one wonder have there been

(41:02):
other cases in the history of insects on Earth where
some sort of insects species or another adapted to some
sort of periodical lifestyle life cycle and it has just
fallen away over time either those species went extinct, you know,
or they evolved into stages they had to essentially become

(41:25):
annual again, or something to that effect.

Speaker 3 (41:28):
Yeah, yeah, I don't know. But I was looking into
this question of like, Okay, well, what would other explanations
be if it's not just this anti predator strategy or
way to avoid parasitoids or predators adapting to your emergen cycle.
And there seemed to be a few ideas floating around
out there. One general class of explanations is that it

(41:51):
is somehow just sort of a remnant of an adaptation
that was formed during the Pleistocene epoch. During there was
a lot more glaciation in North America, and that these
periods of cold unstable weather would move further and further south,
and this pressure, the pressure of unpredictable cold weather, caused

(42:15):
some cicadas to extend their underground periods and it provided
an evolutionary incentive. It rewarded them from coming out less often,
developing these longer and longer periods underground, and then from
that point on it was of course useful for these
species to synchronize their emergencies to all come out at

(42:35):
the same time. There was an incentive in favor of that.
Another hypothesis I've seen for specifically the thirteen and seventeen
year timing of the emergencies is that once there were
ancestral periodical populations in place, there would have been a
biological incentive to avoid breeding with other populations that had

(42:55):
a differently timed cycle, because this could lead to hybridization,
which would interfere with the periodicity adaptation. So like, in
order to be effective as a periodically emerging species, you
really want to be fully synchronized, like have all your
population come out at once within the same place, so
that you can take best advantage of predator satiation and

(43:18):
so forth, and so it's possible there's a disincentive for
thirteen and seventeen year populations to interbreed because that might
unsynchronize them. But I've also seen arguments sort of coming
back against that, so it seems like to some extent,
I think we alluded to this in the first episode.
It still somewhat remains mysterious exactly why these thirteen and

(43:42):
seventeen year time scales have been selected by evolution, but
still leading hypotheses have something to do often with predator satiation.
Either it's too as we've said, to avoid predator and
parasitoid adaptations matching the times of the emergence, or to
avoid interbreeding or to h or maybe it is related

(44:04):
to patterns that emerge during the ice age and have
stuck around ever since.

Speaker 2 (44:09):
Fascinating though anyway you look at it, and it's just
one of the I think the great things about cicada
is there's just so many interesting layers to them, from
their their their basic anatomy and basic physiology, to these cycles,
to then human interpretations of these cycles. Uh yeah, so
much fun. And I guess we might be pressing on

(44:31):
with another episode. I don't know, it's kind of TBD
at this point. Will there be a Cicada Part four
in this series? We're gonna have to to go back
to the notes and take a look. But I guess
you know you'll find out in a couple of days.

Speaker 3 (44:43):
Here see what emerges on Thursday.

Speaker 2 (44:46):
That's right, all right, We're gonna goe and close out
this episode, but hey, you have Cicada thoughts, Cicada observations
right in. We would love to hear from you. Now
that I think about it, I think we had a
listener right in out the Bearside angle and nudged us
forward on that, So you know, I don't recall who

(45:06):
wrote in with that, but certainly that helped nudge us
in this direction. But yeah, right in, we'd love to
hear from you. And just a reminder that Stuff to
Blow your Mind is primarily a science and culture podcast,
with core episodes on Tuesdays and Thursdays. On Mondays we
do listener mail. Wednesdays, there's generally a short form episode,
and then on Fridays we set aside most serious concerns

(45:27):
to just talk about a weird film on Weird House Cinema.

Speaker 3 (45:30):
Huge thanks as always to our excellent audio producer JJ Posway.
If you'd like to get in touch with us with
feedback on this episode or any other, to suggest a
topic for the future, or just to say hello, you
can email us at contact at stuff to Blow your
Mind dot com.

Speaker 1 (45:51):
Stuff to Blow Your Mind is production of iHeartRadio. For
more podcasts from my Heart Radio, visit the iHeartRadio app,
Apple Podcasts, or wherever you listen to your favorite shows.

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