Tuesday, November 14, 2006

Ant Death Spiral

This is one of my favorite things about ants -- the ant death spiral. Actually, it's a circular mill, first described in army ants by Schneirla (1944). A circle of army ants, each one following the ant in front, becomes locked into a circular mill. They will continue to circle each other until they all die. How crazy is that? Sometimes they escape, though. Beebe (1921) described a circular mill he witnessed in Guyana. It measured 1200 feet in circumference and had a 2.5 hour circuit time per ant. The mill persisted for two days, "with ever increasing numbers of dead bodies littering the route as exhaustion took its toll, but eventually a few workers straggled from the trail thus breaking the cycle, and the raid marched off into the forest."

Folks interested in things like self-organization, emergant properties, complex systems, etc. etc. like to point to this as a cautionary tale. I even found a reference to a group programming robots to interact like ants that accidentally produced this behavior in their robots. Apparently you can also reproduce this behavior in the lab by placing a glass jar into the surface. The ants will eventually circle the jar and continue to do so even after the jar has been removed. I assume just army ants. Wow, I wish we had an army ant colony in the lab.

Anyway, in tribute to this fabulously bizarre phenomenon, I made some Ant Death Spiral
T-shirts. Check them out!

Other references:




35 comments:

  1. This is a perfect illustration of our banking system. Now watch them die and a few strong ones will survive to continue the raid off into the forest.

    ReplyDelete
  2. in ants society theres no strong ones... :)
    so watch them die

    ReplyDelete
  3. Ants are around for over 100 million years. So in my opinion this behavior either must be very infrequent or probably has some positive effect, otherwise evolution would have rooted that behavior out. Perhaps the conditions to make a death spiral occur are kinda unnatural, e.g. man-made roads as shown in the video from Panthanal.

    ReplyDelete
  4. this could be a metaphor for christianity or any other religion

    ReplyDelete
  5. Some additional videos and explanation to the phenomenon: http://www.buzzhunt.co.uk/2009/07/15/ants-spiral-of-death/

    ReplyDelete
  6. @Demesos

    This is an incorrect assumption often confused outside of the scientific theory of evolution and how it works. While it is likely infrequent, it does not have to have a positive effect, it simply needs to carry on for multiple generations. For example arthritis is rather detrimental, but it's existence does not mean it is a positive attribute, it is a trade off for the ability to flex joints. Many cases exist where a condition has been adopted through evolution and either harms or has no effect on the organism. What this really is a great example of is an infinite loop, such as in programming. The ant is likely supposed to follow the one in front, and nearly always works efficiently, until the "front" ant (which is really any of them) begins to follow the back, and thus the infinite loop is created. While it is possible for human interaction to cause this, it is much more likely an anomaly that happens because of an inherited trait (not because ants are completely boggled by roads, but because they follow the ant in front of them).

    ReplyDelete
  7. Demesos: If you were correct, we wouldn't suffer from allergies or auto-immune disease. It would probably help to remember that we're not at the end of the evolutionary cycle. If you went to only 50 million years into the evolution of ants, would you say "well, that's a really long time, surely all their bad traits have been bred out?" Probably not, and there's no reason to think 100 million is enough either.

    Also, if a trait is detrimental but generally doesn't completely prevent reproduction (such as male pattern baldness) the trait can stick with the species.

    BUT, more to the point about the article, I think the closest analog in the business world is rule by committee. Rather than making decisions, middle managers tend to pass the ball around, hold meetings, create reports, discuss holding more meetings, "touch base," identify positive action steps, blah blah blah. No one is willing to make a decision and issue orders.

    ReplyDelete
  8. And if you see something like that in your garden is there a chance of stopping it? Perhaps putting something in the way?

    ReplyDelete
    Replies
    1. Very simple:
      Put a physical barrier in the middle of the garden, make sure it is slippery and the ants will be utterly confused, most likely deciding to stop their circling.

      Delete
  9. Sounds like a good way to get rid of a lot of ants at one time without poison to me.

    ReplyDelete
  10. you are all a bunch of idiots

    ReplyDelete
  11. Goodness, what an awesomely cool phenomena. Says so much about evolution and systems. Cool shirts, too, they are now at the top of my "to buy" list. :D

    ReplyDelete
  12. This reminds me of glitches in old video games where your character gets stuck because of a flaw in the level design or a non-playable character blocking you.

    Such a bizarre behavior, I had no idea ants did this.

    ReplyDelete
  13. My dog follows it tail...

    ReplyDelete
  14. I'm sure that you're probably aware of the NetLogo simulation program (massively parallel, intelligent agents)at Northwestern (http://ccl.northwestern.edu/netlogo/) They have a pre-designed model of ant behavior searching for, finding food, and carrying it back to the nest. If the model is correct, such behavior could be created by a flaw in pheromone production, like continuously signaling food when none is available.

    ReplyDelete
  15. It's a bug in the code.

    ReplyDelete
  16. Thanks ants. Thants.

    ReplyDelete
  17. @ Anonymous: I don't disagree. As I said: _either_ being infrequent (which means infrequent enough to not impair reproduction of the organism) or, if not the first then coming with some other effect that compensates for this weakness.
    @ BL1Y: "allergy" is definitive a negative trait, but it comes with a powerful immune system which has a positive effect. So, existence of allergies fits my example, not contradict it.

    ReplyDelete
  18. Fascinating! Has anyone looked to see if there are unique characteristics at the center of these spirals? Either chemical, other physical or social?

    ReplyDelete
  19. it reminds me of the debian logo! (I'm a great fan of debian by the way)

    ReplyDelete
  20. Thanks a ton for keeping this online. beautiful and evocative post
    HP LaserJet 1018 driver

    ReplyDelete
  21. Interesting post. I am always fascinated about how ants that are tiny by themselves all work together in perfect unison, even though it may be self destructive.

    ReplyDelete
  22. This is truly fascinating, how nature works in such smart and beautiful ways...

    ReplyDelete
  23. Truly remarkable! Are these formed for all types of ants or do some produce other shapes? I wonder if you can discern between the shape and the type of ants that made them...

    ReplyDelete
  24. Why would these army ants be killing themselves in a spiral? Doesn't seem very logical to me. IF they would just march forward they wouldn't be exhausted and die.

    Knotts Berry Farm Coupons

    ReplyDelete
  25. Amazing! There must be some sort of mathematical formula to predict and find a relationship between the radius of the circle to the amount of ants or the time until exhaustion of the circle.

    ReplyDelete
  26. The spirals are amazing...the whole phenomenon is just crazy, especially the part of it happening with ant robots!

    NJ SEO Services

    ReplyDelete
  27. Sounds like a good way to get rid of a lot of ants at one time without poison to me.

    ReplyDelete