Ants Can Support 5,000 Times Their Body Weight Before Losing Their Heads

The ability of worker ants to carry many times their own body weight is well documented, but new research on heavy-lifting ants reveals that the neck joint of a common American field ant can withstand pressures up to 5,000 times greater than its own body weight.

Writing in the Journal of Biomechanics, entomologist Dan Crosfield and researchers from The Ohio State University said that the ant's strength far exceeded their initial estimates.

"Ants are impressive mechanical systems - astounding, really," said Carlos Castro, a professor of mechanical and aerospace engineering at Ohio State. "Before we started, we made a somewhat conservative estimate that they might withstand 1,000 times their weight, and it turned out to be much more."

While an ant carrying a huge leaf on top of its tiny frame provides sound analytical evidence that the insects can carry weight far in excess of their own, Castro and his colleagues reached their conclusions through a more mechanical approach: They took the ants apart.

"As you would in any engineering system, if you want to understand how something works, you take it apart," Castro said. "That may sound kind of cruel in this case, but we did anesthetize them first."

For the research Castro and his team chose the Allegheny mound ant (Formica exsectoides), a common ant not particularly know for its ability to lift.

From there, the team essentially disassembled the ant, dismantling it into its component parts as if they were reverse-engineering it.

The ant specimens were imaged with an electron microscope and a micro-CT scanner, then they were refrigerated to induce anesthesia before being glued into place on a specially designed centrifuge that measured the force necessary to deform the neck and eventually separate the head from the ant's body.

The concept is similar to a spinning carnival ride where passengers are pinned to the wall of the ride by centrifugal force as the floor drops out from beneath them.

"In the case of the ants, their heads were glued in place on the floor of the centrifuge, so that as it spun, the ants' bodies would be pulled outward until their necks ruptured," the university said in a statement. "The centrifuge spun up to hundreds of rotations per second, each increase in speed exerting more outward force on the ant. At forces corresponding to 350 times the ants' body weight, the neck joint began to stretch and the body lengthened. The ants' necks ruptured at forces of 3,400-5,000 times their average body weight."

The researchers said they hope that their understanding of the mechanics of the ant's anatomy and its ability to withstand force will be of use in future robotics designs.