DO ANTS HAVE A STRAINED RELATIONSHIP WITH WATER?

Ants and water? They go together about as well as camels and winter sports— or so many people would imagine. Ants are very closely associated with a dry background. But when the rain begins to fall, these industrious land insects must cope with the hardships it presents—and they do, with flying colors, even though the tiniest trickle becomes a raging torrent for them.

When caught in a deluge, ants are able to hook their bodies together by the hundreds to form bridges or rafts. If an ant is caught out in the elements on its own, it can make a solo journey across a stretch of water thanks to its hydrophobic exoskeleton and legs that are covered in fine waxy hairs that repel water. The little creature is aided by its low weight (about 5 mg) as well as water’s surface tension, which creates an elastic interface between air, liquid, and ant.

But there’s a catch. The higher the temperature, the lower the surface tension of the water, because heat makes molecular bonds dissolve. This is the ant’s downfall, but even immersion in water does not mean certain death: Instead of lungs, ants have tiny openings on their bodies called spiracles, which connect to tracheal tubes. These tiny respiratory tubes are in some cases smaller than a thousandth of a millimeter. Through these the oxygen from the air reaches the body’s cells directly—rather than requiring blood for a middleman, as is the case in humans. This ingenious system of chambers ensures enough air in an emergency. The length of time an ant can survive underwater depends on how much air is stored in its tracheal system, which in some cases can be shut down: In this way an ant is able to “hold its breath” for several hours at a time. The reason: In the trachea gas exchange occurs at a much slower rate than in a lung. This affords a cushion in the event of a sudden lack of oxygen, but it only works with small bodies. Carpenter ants, which can be even longer than half an inch, will suffocate—or break: That’s because the tracheal system requires a disproportionate amount of space to absorb enough oxygen, and this leads to extensive areas of perforation inside the insects’ bodies. A compact ant will emerge from its submersion somewhat woozy—but after a short recovery period, it will be crawling along as feistily as ever.