think or thwim

Deborah Gordon studies how the interactions of ants following simple rules can result in the more sophisticated behaviors of the colony without any executive ant in control.

ants, deborah gordon

This is the best segment of a documentary called Ants! Nature’s Secret Power. From the movie:

The structure covers 538 square feet and travels 26 feet into the earth. In it’s construction, the colony moved 40 tons of soil. Billions of ant loads of soil were brought to the surface. Each load weighed four times as much as the worker ant, and in human terms, was carried over 1/2 mile to the surface. It is the equivalent of building the great wall of china. It is truly a wonder of the world…

So we filled it up with concrete. Sorry ants.

ant nests, ants

BBC News is reporting that researchers at the University of Bristol have discovered Panamanian army ants using their own bodies to plug holes in the route from a food source to the nest.

Dr Scott Powell:

When the ants bump into a hole they cannot cross, they edge their way around it and then spread their legs and wobble back and forth to check their fit. If they are too big, then they carry on and another ant will come along and measure itself in the same way. This carries on until an appropriately sized ant plugs the hole.

He also said the ants stay in the same position for hours until the traffic dies down at the end of the day. Here’s some more examples of ants using themselves to form living bridges:

The guy that took this video says the ant being pulled up at the beginning just finished a 30 minute shift.

:: 3quarksdaily

ants

Ants are fascinating because they are stupid. They seem to totally lack free will and a sense of self. They are simple robots programmed to do a job, and they work like machines. The documentary Ants! Nature’s Secret Power shows grass cutter ants continuing to harvest grass in the middle of a grass fire right up until the instant they die from the heat. The individual ants aren’t programmed to protect themselves by running from the fire. They are programmed to take care of the colony by gathering food. There is no selfishness among the ants.

Bert Hölldobler and E.O. Wilson argue that we should think of the ant colony as an animal rather than the individual ants. The ants are like cells making up the body of the animal. Slime molds are the same way. In fact, at first we thought slime molds were the organism until we discovered that they are actually swarms of smaller individuals.

In an ant colony, the queen is not a ruler. She’s just an egg producer. Complex behaviors like mealy bug herding and fungus farming emerge from interactions between individual ants following simple instruction sets. But even without a designated leader the colony does affect the actions of the individual ants.

In the early 1990s Deborah Gordon at Stanford University conducted some experiments in which she painted foraging ants green and housekeeping ants blue. Then she introduced additional food to the nest. The next day some of the housekeeping ants had switched to help deal with the extra food. Likewise, when she messed up the nest, some of the foraging ants switched to housekeeping duties.

Gordon’s experiments revealed that individual ants get some kind of signal from the colony. At the time the mechanism was still a mystery. Someone’s probably proven it’s pheromone controlled since then, but I haven’t run across that yet. The important point is that there’s a feedback loop between the colony as a whole and the simple rules governing each ant.

Like ant colonies and slime molds, humans consist of a collection of stupid cells. The big difference, and the reason we are so reluctant to classify ant colonies as beings, is that our cells can’t live on their own. However, neither can an ant. An ant separated from it’s colony has a very short life expectancy. The only exception is a queen that has enough fat stored to start a new colony, but if she can’t get some workers raised before her fat store runs out, she’ll die too. With our cells, the demise is just more immediate.

animal behavior, ants, bert holldobler, consciousness, deborah gordon, emergence, eo wilson, insects, swarm behavior

This is how fire ants first arrived in my area. During a flood in the 1980s rafts of fire ants floated to the shore on the flood waters. The rafts are made entirely of fire ants. The individual ants on the bottom die, but the colony survives.

Ants evolved from wasps, and the fire ant still has the sting. If you accidentally step on a fire ant mound, they rush to the surface and attack in mass. First they bite into your flesh to make themselves hard to remove. Then they sting you, injecting a venom that gives a very painful burning sensation. I’m not sure how this fellow managed to get so many stings. Most people totally freak out and manage to limit the damage to less than 10 stings. However, a fire ant attack will occasionally kill small animals like birds, and some people have fatal allergic reactions to the venom. People that live in fire ant country watch where they step.

Fire ants are native to South America where they are kept in check by natural predators. However, they were accidentally introduced to the US around the 1920s when they hitched a ride an a cargo ship. There are no natural predators in the US, and the fire ants push out the native ant species as they spread north and west. RIFA stands for Red Imported Fire Ant.

This figure was from 10 years ago. They have now covered the entire southern portion of the United States. They invaded Australia in 2001 and Taiwan in 2004. They have also spread to China and the Philippines lately.

ants, insects

In 2000 Toshiyuki Nakagaki announced that an amoeba-like slime mold was able to find the shortest distance through a maze, which is nearly the equivalent of saying a bit of Jello was able to jump up and run out of the refrigerator by itself. How did a nearly inanimate object solve such a complex problem?

(food is yellow and slime mold is white in the picture to the right)

First, what is a slime mold? From the introduction to Steven Johnson’s 2001 book, Emergence:

If you’re reading these words during the summer in a suburban or rural part of the world, chances are somewhere near you a slime mold is growing. Walk through a normally cool, damp section of a forest on a dry and sunny day, or sift through the bark mulch that lies on a garden floor, and you may find a grotesque substance coating a few inches of rotting wood. On first inspection, the reddish orange mass suggests that the neighbor’s dog has eaten something disagreeable, but if you observe the slime mold over several days — or, even better, capture it with time-lapse photography — you’ll discover that it moves, ever so slowly, across the soil. If the weather conditions grow wetter and cooler, you may return to the same spot and find the creature has disappeared altogether. Has it wandered off to some other part of the forest? Or somehow vanished into thin air, like a puddle of water evaporating?

Slime molds are really groups of tiny amoeba which are normally sliding around the forest floor individually. Occasionally they will coalesce into a larger blob. There is no central commander telling the individual cells when to come together or disperse. Like ants, they use pheromone trails. The individual cells release pheromones based on their assessment of the conditions. Using a type of chemical democracy, when the pheromone trail gets intense enough the slime mold cells pile together to form a larger being.

When you think of a slime mold like an ant colony it becomes clear how it solves the maze. Scout cells spread out, and pheromone trails eventually build up along the successful paths helping the individual cells find the most efficient route.

Here’s a close up time-lapse video of a slime mold moving.

Slime molds are so close to being both plant and animal that it’s like they can’t make up their minds. And they’re thinking now that maybe this is who’s been running the earth all this time.

- David St. Hubbins, This is Spın̈al Tap

ants, emergence, slime molds, time lapse

Walter Tschinkel at Florida State University has been making plaster casts of harvester ant nests to study ant architecture and behavior.

From Tschinkel’s paper (more pictures at the bottom):

Nests grow by simultaneous deepening, addition of new chambers and/or shafts and enlargement of existing chambers. As a result, the vertical spacing between chambers is similar at all nest sizes, and the relative distribution of chamber area with relative nest depth did not change during colony growth (that is, the size-free nest shape was the same at all colony sizes). Total chamber area increased somewhat more slowly than the population of workers excavating the nest.

I’d like to see what happens inside one of these when it rains. I found this. Does anyone have anything better?

ant nests, ants, architecture, insects

The movie was removed from Google Video, but you might be able to download it using bittorrent. I haven’t tried it myself. Somebody posted my favorite part to YouTube.

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If you’ve never considered ants to be particularly interesting, this should change your mind.

This film is full of incredible stuff. Here are some notable examples:

• Indonesian ants have domesticated mealy bugs and feed on sugar and vitamin rich honey dew excreted by the mealy bugs. The ants are nomadic, periodically moving their mealy bug herds to new plants for fresh grazing.
• When a colony is disturbed, scout ants spread out looking for a new site. The site is selected by a form of democracy. Individual ants vote by leaving pheromone trails to preferred sites. At the end of voting, the site with the strongest pheromone trail is used.
• Grass cutter ants use relay teams to transport food. Each team covers a set distance and hands it over to the next team.
• Wood ants harvest tree resin to use as an antibiotic and fungicide.
• Grass cutter ants cultivate underground fungus gardens. They build gravity ventilation systems to maintain desired temperature, humidity and CO2 levels.

My favorite part is toward the end. They fill a grass cutter ant hill with concrete. After it dries they excavate the site revealing the underground ant architecture:

For more information check out: Bert Hölldobler & E.O. Wilson | The Ants. It won the Pulitzer Prize in 1991. It’s been on my Amazon wishlist for years, but I haven’t been able to justify paying $200. Hölldobler is listed as a scientific consultant in the credits of this film.

ants, bert holldobler, documentaries, eo wilson, insects