What do ants do when it rains?

SDStaff Doug replies:

Ordinary soil is very porous, with lots of air spaces. In addition, the surface tension of water is such that it tends to pool on the surface and percolate into the ground slowly, unless the soil is very sandy. The bottom line is that there is so much air trapped in the soil itself, as well as in the ants’ tunnels, that they can breathe freely for weeks even if the area is totally submerged, since they require so little oxygen. There may even be some gas exchange between the trapped air and the water, further prolonging the process, similar to the system used by diving beetles, known as a “physical gill,” or plastron. Rain is really meaningless to anything that small — only larger things like earthworms may have trouble, and even then the rain has to be quite heavy, and the worms need to be close to the surface where the soil saturation is greater.

SDStaff Doug, Straight Dope Science Advisory Board

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