girls gone feral

I read that too! I don't see how it explains why they all swarm together, though - wouldn't you rather fly off somewhere that doesn't have tons of other locusts?

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virginia-fell.livejournal.com

Maybe as a group they have a better chance to find non-each-other food? I'm just wondering here, so this is hardly a scientific hypothesis, but maybe their likelihood of finding eatables is higher if they stay with other creatures like themselves (particularly since those other locusts are also evidently tasty), even if the downside is that they're more likely to get eaten themselves.

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You're overthinking it. Locusts have two imperatives in their brain once they go into swarm mode: Eat and Don't Get Eaten.

When they go into swarm mode, they're all in a group of other locusts. First thing they see that they can Eat: the locust in front of them. First thing they hear that's coming to Eat them: the locust behind them.

End result: All locusts swarm wildly in a randomly determined direction, frantically chasing the locust in front of them and avoiding the locust behind them, until they come upon some *other* food that they gobble up. As soon as the food is gone, all the locusts suddenly notice each other again and start chasing each other again, and the swarm moves on. This accounts for the bizarre pseudo-intelligent "ravenous" behavior of a locust swarm apparently zeroing in en masse onto a patch of food and instantly abandoning it once it's consumed for another one like a superintelligent hivemind, when in fact it's almost the *opposite* of a superintelligent hivemind -- it's the result of maybe even one single locust spotting some food somewhere and desperately sprinting toward it with the whole swarm of ravenous locusts following it for no other reason than they want to eat him while avoiding being eaten by the ones just behind them.

It's almost mathematically simple. There is no higher-order thought process going on in the locusts' brains beyond this. For a locust to strike out on its own from the swarm would require that locust to ignore Imperative #1, Eat, wholly in favor of Imperative #2, Don't Get Eaten, and that would be impossible for a hungry locust -- the need to Eat that locust hovering just out of your reach is overpowering even considering the threat of the locust just behind you trying to Eat you. Hunger and fear balance each other out almost completely and keep you locked within a specific place in a surprisingly regimented-seeming social order composed of nothing but your blind hope that you'll catch the locust in front of you before the locust behind you catches up (if you, as a locust, were capable of complex emotions like "hope", which you are not).

A *smart* locust might think "Hey, if I drop out of the swarm and head off on my own, I'd be at no risk of being eaten, and even though I don't see any *immediate* sources of food out *there* as tempting as that luscious locust in the swarm just ahead of me, as a rational long-term planner I must presume there are other food sources there somewhere that if I'm smart about it I won't have to share with the swarm as a whole." But locusts are, almost by definition, not smart, and any locust that stayed still long enough to try to think this concept through would get eaten.

It is, I suppose, sort of a metaphor for capitalist society.

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virginia-fell.livejournal.com

Yeah, that's probably got the right of it.

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This doesn't actually explain things since locusts are only *in* swarm mode once there's a huge number of them. Normally they do not seek out the company of other locusts except to mate, but in swarm mode they actively follow the others. Their entire biology and behavioral programming changes considerably when they reach a certain population density.

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Are you saying why, from the big-picture biological standpoint, swarm mode exists rather than what's going through the individual locust's (lack of a) mind during swarming?

That's obviously a more complicated question. I was talking about what set of instincts motivates the individual locust to stay in the swarm, not why swarming evolved in the first place. Swarming probably settled into place as a behavior because swarms do a good job of clearing the neighborhood of competing species that don't swarm, and because it provides a built-in mechanism for scattering the genetic material of the species widely around the area.

I think larger questions of "why" may be mistaken -- biological effects like swarming, just like social effects like the subprime mortgage market, are things that happen due to emergent self-reinforcing patterns that last because they last. They aren't necessarily "better" than not having them. All you need for some kind of swarming behavior to bootstrap itself into existence is a glitch in an insect's normal serotonin response to social interaction with other insects where it goes into a positive feedback loop -- the bug gets *more and more excited* just by being around other bugs until it goes completely insane. Then evolution just prunes out the *totally* destructive forms of insanity while the ones that aren't quite destructive enough to wipe out the species persist and keep on crufting more and more bits and pieces onto themselves, until we reach the point where the effect has evolved into a full-on physical transformation like we see now.

I wouldn't say that swarming is necessarily a beneficial adaptation -- like with most such things it has upsides and downsides. The massive habitat shifts and swings in population caused by swarming probably make a species more vulnerable to certain forms of habitat loss -- this is basically why the Rocky Mountain locust went extinct en masse with the arrival of agriculture.

Again, all kind of analogous with the subprime mortgage crisis. As with the subprime mortgage crisis, it's kind of important to remember that the individual beings involved aren't thinking anything but Eat Or Be Eaten, and the system as a whole is a product of random chance that is, if anything, dumber than the individual beings. (The anthropomorphic thinking of asking "Why did God make locusts to swarm?", difficult a habit as it is to shake, can lead to some dangerous errors in thinking. It's even more dangerous when people start applying it to things God even more obviously didn't make, like market capitalism and speculative finance.)

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I'm actually critiquing both, but primarily what's going through the locust's circuitry during swarming.

Swarm mode entirely changes their behavior in ways that can be observed even when you isolate them and observe them individually. An animal that would normally avoid or be relatively indifferent to others (except to mate) will, if you stroke their legs enough times over a few hours, go through several molts, change colors, and all of a sudden seek out other locusts.

But locusts clearly have an "eat" instinct and a "don't be eaten" instinct prior to swarm mode. If the behavior were truly a response to the "eat and avoid being eaten" instincts, then you'd expect, for example, locusts who aren't in swarm mode to go into swarm mode immediately when a swarm descends on their location, since they were already trying to eat and not get eaten before that swarm showed up. But they don't.

Maybe the only thing that changes is that they now see other locusts as potential food, but there's clearly a switch that turns on that changes their behavior into something it wasn't before. And if this video is any indication, it's not like even swarming locusts are constantly attempting to eat each other (see, for example, the shots where a bunch of red/orange locusts in swarm mode are just chilling out in a container with no food in it, attempting to eat the one green locust but otherwise appearing pretty peaceful).

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But they spend most of their lives in solitary mode and appear to find food just fine then; the main thing that makes them swarm is population, not scarcity. It's sort of odd.

Maybe you want to follow the group to make sure that you don't keep flying somewhere only to find that the rest of the group has already been there and eaten everything? But this doesn't explain why the others are swarming. I dunno.

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The bugs don't "want" anything. The bugs go completely bonkers insane and lose the capacity to do anything but chase ravenously after their brethren.

The *species* doesn't "want" to swarm either -- the species is locked into a certain pattern as a result of random evolution. There are certain benefits to swarming, sure, but you have to balance that out with the costs -- keep in mind that the vast majority of insect species *don't* swarm, and that therefore on balance swarming can't be that great of a strategy.

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qianian.livejournal.com

Generally in animal behavior, clustering happens in populations where resources are clustered. When resources are evenly scattered around, mating habits and individual territory are spread out. In this model, swarming should be beneficial only when resources are pooled in isolated "oases," we might imagine them.

Is this true?

Food is not the only resource. Mates are also resources. I know that predatory birds eat up locusts and, as documented by Scott Weidensaul, have suffered dramatically in agricultural pesticide use. Ironic, but he reported birdkills where you couldn't see the ground for the bodies.

Just some ideas.

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it is true that locusts most predictably swarm when a wet period (with lots of breeding) is followed by a very dry period, in which locusts all congregate around the food and water that's still around. So I can see the behavior being a response to food clustering.

That said, it does get way out of hand: the last catastrophic locust swarm in 1988 flew over all of northern Africa and the Middle East, making its way all the way up to Iran. I am guessing that there was probably somewhere in that whole region that wasn't suffering extreme drought, and that an optimal solution would have been for the locusts to spread out along that expanse. Obviously they weren't programmed to find that solution; I think that the switch to swarming mode is irreversible and continues for their lifespan. Perhaps just because a gene containing an "off" switch never showed up at the right time, or wasn't sufficiently advantageous given that locust swarms of that size are pretty rare.

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i read a book once where, after the locusts came, the morning dew on their wings made them unable to move on, and the people in the village where the locusts had settled went out and gathered up the locusts and ate them. apparently they were yummy.

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q10.livejournal.com

most locusts are safe to eat and fairly nutritious, and, when they're around, they tend to be the only thing there is to eat (because they've eaten everything else), this means that most societies that have to deal with the occasional locust swarm are also occasionally in the locust-eating business (this may be the reason that locusts are the only kosher insects).

my favorite quote about locust-eating comes from Nigerian locust-harvester Gambo Ibrahim (quoted here):

‘I mean, yes, the locusts are eating up our crops, but we are also eating them up and making money to boot. So, both man and locust are losers, but I think they are worse off because we are eating them.’

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hmm. that bit at the end of the article makes me wonder. locusts were one of the ten plagues, and the Jews were permitted to eat them but God took the locusts away...you'd think He'd leave some for the Jews but take them away from the Egyptians.

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Although the Bible doesn't specify it for this particular plague, in general there are repeated references to the fact that God only sends the plagues against the Egyptians and anywhere where the Israelites live is supernaturally spared (the proverbial "land of Goshen" where most of the Israelite slaves had their residences). The ultimate example of this is obviously the rite to protect the Israelite firstborn for Pesach, but you also see it with the plague of darkness (where only the land of Goshen remained lit), the plague of livestock (only the Israelites' animals survived) and the plague of flies.

Admittedly given that Israelites were supposed to be a slave race at this time a massive crop failure would leave them just as screwed as everyone else. But this was already the eighth plague -- God has pretty much committed to a scorched-earth strategy by now.

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Admittedly given that Israelites were supposed to be a slave race at this time a massive crop failure would leave them just as screwed as everyone else.

Given that the Hebrews weren't going to be staying around much longer, they probably didn't suffer most of the serious ill effects. And also, a locust day is a no-forced-work-in-the-fields day! Just sit back, fry up some bugs, and wait for it to be over. If the locusts eat enough crops and it's long enough after planting time, you may not even have to work that hard in the fields for the rest of the growing season! Win.

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Well, the original quote was about a Talmudic tradition that the Egyptians tried to gather up the locusts to eat them and God, in his vengeance, driving all the locusts away en masse and then causing all the stored locusts to spoil.

If this affected the Israelites too then that would make for pretty hard times all around.

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Ah, okay. That's pretty easy, though, to see how it could only affect the Egyptians.

I just remembered, though, that in any case it doesn't matter that locusts were kosher, since kashrut as it currently exists didn't exist until after the flight from Egypt. Technically, at that point in time, the Hebrews could eat the frogs, too. They just couldn't have eaten them alive.

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Jews can eat locusts, but it's still preferable to not have locusts at all, since they will eat your entire crop for the year. I imagine that locust meat gets boring after a while, and there's no chance that you can capture the same caloric content out of the locusts as you could out of your crops - you're just not going to catch them all, and energy is lost whenever you go up a level in the food chain. Hence the comment that "both man and locust are losers" when locusts swarm.

Also, they're really scary. In order to hunt them, you need several layers of clothes, heavy boots, and you have to do it at night when they're not flying as much. Imagine going outside in this:

but without a car around you. You're really not going to be happily thinking "hey, I can eat those!"

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in the book i read, it sounded like the locusts were gorged and damp and just sitting still.

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But as you said, that was because the dew made them too wet to fly. In the daytime when they're dry, they're freaking scary. And in any case, they were gorged because they'd eaten all the foliage off of the plants in the area.

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okay but...they harvest them when they can't fly. they take them all, and then by the time they're dry, they're dead.

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Right. But that doesn't mean you're happy they came in the first place. And most of the time, they can fly and can't all be harvested when they can't fly. I guess I'm not sure what the point we're arguing over is?

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I don't think anyone said that locust swarms were ever overall good news. At the same time, I think you may be overstating the degree to which harvesting locusts is "scary" to people who've lived in the area a long time and are familiar with the routine for dealing with locust swarms.

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harvesting locusts isn't scary. You do it when they're sluggish. But even then you have to put on loads of layers of clothes (I got this information from a direct interview with a locust harvester). Actually walking through an actively flying locust swarm is most likely pretty scary no matter how used to it you are - they are big enough bugs to hurt when they fly into you, and they're guaranteed to do so. Besides, I imagine that the reason locust harvesters wear work boots and several layers of clothes is because they can bite.

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aryky.livejournal.com

I don't think anyone said that locust swarms were ever overall good news.

Actually, assuming that the book

l0stmyrel1g10n is referring to is Things Fall Apart, Chinua Achebe actually does kind of imply that the locust swarms are really good news. Google Books helpfully has the entire passage online here, but key quotations include "almost immediately a shout of joy broke out in all directions," "'Locusts are descending,' was joyfully chanted everywhere," and "Everyone was now about, talking excitedly and praying that the locusts should camp in Umuofia for the night" (39).

When I read Things Fall Apart, I didn't know very much at all about locusts, so I think I just assumed that this was something Achebe had put into his book as part of his strategy of showing a distinctly African culture as opposed to a European one, since European and European-derived cultures generally fear locusts. Given the points being made about the devastation that locust swarms actually cause in Africa, it's hard for me to see what Achebe is actually getting at in making a locust swarm a cause of joy in his book. . . it's not as though there's no agriculture in Umuofia; in fact, the culture centers around the growth of yams. Could that point be what makes the difference? The part of the yam that people eat lies under the ground; maybe the locusts can't get to it? In the passage I quoted, they're described as eating only the trees and the grasses. . . but I don't know nearly enough about locust swarms to see if this makes sense, so maybe Achebe just got his details wrong in this case?

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I think that it says the locusts came during the harvest season, so yeah, the fact that they ate the foliage of the yam plants wouldn't have been such a bad thing - they can't eat the yams, and it doesn't matter as much if the yam plants lose their leaves since they're about to be dug up anyway. And it was a novelty, so it might have been more exciting for that reason as well.

It's not really European-derived cultures that fear locusts, though, since Europe doesn't even get them. We get our fear of locusts from the Bible, which describes cultures in the Middle East and Egypt.

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aryky.livejournal.com

The sense that I got from my colonial and post-colonial literature seminar is that Things Fall Apart was written to address two main audiences - Igbo people whose culture had been altered by colonialism and wanted to find out about their culture before that had happened and Westerners who weren't aware of pre-colonial Igbo culture at all. In that context, I saw Biblically-inspired fear of locusts v. embrace of locusts as representing a post-colonial/Westernized/Christianized attitude v. a pre-colonial, un-Westernized Igbo attitude. While obviously there are non-European cultures that fear locusts, and obviously the Europeanized attitude towards locusts ultimately derives from one of these sources, cultures that are neither Westernized nor Igbo seemed less relevant to this particular book.

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orawnzva.livejournal.com

Not a locust per se, but there's a variety of grasshopper that's considered a delicacy in Oaxaca (a district of southern Mexico), where they're called chapulines. I had them as a snack when I visited Oaxaca with my parents. Mmmmm!

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polexa.livejournal.com

There's an interesting TED talk (or maybe it was Radio Lab?) about emergent behavior...

I think it was a TED talk because there was video.

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object-holder.livejournal.com

Amazing!

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What if you could insert robotic drones into their midst that emitted pheromones, and STEER them all over the place?

Well, I'm not really an expert, but I think in order to manipulate the pseudo-random behavior of a locust swarm to a reliable degree, a high enough percentage of the locust swarm would have to be under your control -- potentially thousands of drones -- that it wouldn't really be worth it. If you had the resources to do that you could probably just kill the locusts outright.

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