These Ants Have a Revolutionary Escape Strategy

Trilobites Why reinvent the wheel when you can become it? Ants are bristling with defense weaponry. Different species might sting their enemies, bite them with powerful jaws or shoot them with jets of formic acid. Some even explode.

But Myrmecina graminicola — an ant about the size of a sesame seed — doesn’t want to get into all that. According to research published last week in Scientific Reports, if one of these ants encounters danger while it’s on a slope, it makes a practical choice: It tucks itself into a little ball and rolls away. It is the only ant known to move in this way, and one of few rollers in the animal kingdom over all, said Donato Grasso, the paper’s lead author and an ant ethologist at the University of Parma in Italy. Dr.

Grasso and his colleagues first spotted this unique behavior while scanning the forest floor during a trip to one of their field sites in Fornoli, Italy. (Many entomology discoveries are made this way: “When you are a biologist interested in insects, it is impossible not to look at the ground,” Dr. Grasso said. ) The team found a few colonies of M.

graminicola, which are so small and elusive they often go unnoticed. When the insects were menaced by spiders and other ants, “they curled their bodies and disappeared” into the leaf litter, Dr. Grasso said. “They rolled away.

” The research team decided to take some of the ants back to the lab. It was difficult to find them, and when the researchers picked the ants up, they would sometimes somersault out of their hands. But eventually, they caught some living inside fallen tree galls. In the lab, the researchers used slow motion video to tease out the ants’ choreography.

Roughly: A ready-to-roll ant tucks in its head and pulls its abdomen forward to form a ball. It then lifts its legs up and tips itself forward to rest on its mandibles and antennae, which balance it like arms, Dr. Grasso said.

“A final push with the hind legs, and it’s off.”