Ants rank with beavers as some of the best-known architects of the animal world. Ants build the elaborate colony structure by hollowing out the area with their mandibles, grain by grain. Unless the soil dries out dramatically, the chambers will keep their form. But how ants manage to construct such well-planned underground structures remains a mystery, according to ant expert Walter Tschinkel of Florida State University.
"They do this without a blueprint, without a leader and in total darkness," Tschinkel says. To get a glimpse of the elaborate systems of passageways that ants build underground, Tschinkel makes casts of ant colonies, pouring molten metal, paraffin wax, or orthodontic plaster into the hollows and then excavating the result. "You can see that there is a structure in relation to depth," Tschinkel says, observing that the ant colonies have most of their chambers closest to the surface, with smaller, more spaced-out chambers farther away. "To do that, the ants have to know where they are in relation to the surface," he says. How they do it remains unknown, but Tschinkel's hypothesis is that ants can gauge depth by sensing the carbon dioxide content in the soil (he found that the amount of carbon dioxide increases with depth).