How Cockroaches Crash Into Walls and Keep Going

Anyone who’s tried to kill a cockroach knows that the ancient pests have some world-class evasive maneuvers. Or at least they appear to.

The agility of cockroaches may owe less to lightning-fast reflexes and fancy footwork than to their tough, shock-absorbent bodies. According to a new study, American cockroaches can run full-speed into walls and other obstacles because their exoskeletons allow them to recover quickly with hardly any loss in momentum.

“Their bodies are doing the computing, not their brains or complex sensors,” said Kaushik Jayaram, a biologist at Harvard University and lead author of the study, which was published in the Journal of the Royal Society Interface.

The findings — which were further validated by a tiny, cockroach-sized robot — could influence the design of the next generation of robots that run, jump and fly.

The escape methods of the American cockroach are legendary among scientists. Studies have shown them to be among the world’s fastest insects, reaching speeds of up to 3.4 mph (or about 50 body lengths per second). They can pivot quickly, scamper across ceilings and disappear into tiny crevices.

But they are also known to frequently collide with obstacles. Jayaram wanted to know whether those collisions counted as missteps or were part of a strategy that favored speed over accuracy. To find out, he and a team of researchers focused on one of the insect’s signature moves: the blink-of-an-eye transition from running along a floor to scaling a vertical wall.

Using high-speed videography, the researchers recorded 18 male American cockroaches repeatedly running across an acrylic track with only one climbable wall (other walls were coated with petroleum jelly). When they viewed the tapes in slow motion, the researchers were surprised to discover that 80 percent of the time, the insects were simply crashing headfirst into the wall at top speed before making the transition. Other times, they were angling their head upward and using their legs to slow down before reaching the wall.

It turns out the cautious approach wasn’t necessary. The roaches that ran headlong into the wall could make the upward shift just as quickly — in about 75 milliseconds — the researchers found. Apparently, the roaches preferred to run full speed knowing their exoskeleton could take the hit.

To be sure the roaches were relying on their bodies and not their wits, the researchers ran similar tests with a tiny, cockroach-inspired robot that had no sensors or feedback mechanisms. The results were similar, appearing to confirm Jayaram’s conclusions.

The findings could prove helpful to engineers as robots become smaller, softer and lighter, Jayaram believes.

“There is an increasing trend to make robots smarter and more capable, so that they can operate effectively indoors or within cluttered natural environments,” he said.

If the current study is right, “small robots can be built with simple, robust, smart bodies to safely bump into obstacles instead of using complex and expensive sensing and control systems,” he said.

His message to engineers? Just follow the cockroach.