Ants are great tunnelers. That’s how they make their nests underground. But even they run into traffic jams, like this one here. That’s not surprising. But the solution is. Experiments with fire ants showed that the key to avoiding jams and solving ones that do occur is idleness — 30 percent of the ants do 70 percent of the work. And that turns out to be ideal. Add more ants to the working pool, and productivity suffers. It’s not that any particular ants are lazy, or that they know how to avoid jams completely. Ants do pile up. But they’re easily discouraged by a jam and good at backing up and turning around, allowing the remaining workers to continue digging. Some of the ants don’t even go near the tunnel. The researchers tested their ideas about optimal ant behavior using robots and magnetized spheres. With simple instructions to gather the spheres, the robots all rushed to work at the same time. The result: gridlock. But with some idleness programmed in, the robots were more productive. Here you can see the original group versus ones programmed to think more like ants. In the real world, this kind of programming could make robot swarms more effective at searching disaster sites or delivering drugs inside the body. So why don’t ants just make wider tunnels with more room for digging? Well, here’s what happens in a wider tunnel. Sometimes, it’s hard to hang onto the sides. And sometimes, they completely lose their grip. How embarrassing.