44. Ant Spirals of Death

04 Mar

FACT: Ants are wonderfully strong, durable and efficient creatures, unfortunately whilst the colonies are smart, the individual ants are not, meaning that stupid things such as circular milling a.k.a ‘Death Spirals’ can occur. They are often found on pavements or other smooth surfaces in Uruguay, Argentina and other South American countries.

Here is one such spiral:

So why does this happen?

Death Spirals only affect ants especially dependent on scent trails. You see, the blind ants cannot navigate back to their colony on their own, so instead each one follows a scent trail which is a stream of chemicals coming from the ant in front saying to the ant, ‘This way!’

This is a good system, and it works as every ant lays down a stream of these chemicals so no ants lose the scent, unfortunately things can go wrong. One leading ant, no different from any other, makes an error, it turns off the path and keeps going in a circle until it meets its own stream – and as we all know you should never cross streams.

The ant loops around in a circle and is now stuck in a loop, so are the ants following it and furthermore all of the ants following them. a Spiral has begun. Over time thousands upon thousands of ants join and follow the loop, forming a large, shifting, writhing and spinning mass of legs and mandibles. This is the ‘Death Spiral‘. The word ‘Death’ is in there with good reason –  no ants will survive this.

Why? because ants are stupid. Due to their inability to see the world the ants just carry on, running at full pelt along their circles their loops with the false belief that they are approaching their colony. Unfortunately its a road to nowhere and they will not stop. They will eventually die of exhaustion, running in their loops until they collapse. There re never survivors. Fortunately for the colony there are always more ants


Posted by on March 4, 2011 in Articles, Trivia


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2 responses to “44. Ant Spirals of Death

  1. John Aird

    March 4, 2011 at 11:45

    An extraordinary phenomenon, thanks for that video. If anyone’s interested in a bit more reading around pheromonal organisation in ant colonies, here’s an interesting paper published in Proceedings of The Royal Society in 2002 (

    Also, according to Wikipedia, the man who first described the behaviour observed an ant mill 365m in circumference.

    John ( – Science ‘n’ That)


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