Walter R. Tschinkel with plaster mold of nests and tunnels Photo by Charles F. Badland

As an entomologist interested in how ants live underground, I have long wished I could see into the earth and examine every detail of their nests and tunnels. The next best thing, I decided, would be to use their nests as a mold for casting these complex living spaces in plaster. To begin the process, I pour orthodontic plaster (which is stronger than plaster of paris) down the entrance burrows and let it penetrate into the farthest recesses of a colony's nest. Then follows the long, laborious process of progressive excavation and reassembly of the resulting casts. The finished and assembled model is like a positive print of a photographic negative, a record of the art that ants have practiced for millions of years. Collectively the diminutive insects create a giant structure, one sand grain or bit of earth at a time—the product of evolved behavioral programs within each tiny worker's brain.

Nest size varies enormously from species to species. Eastern woodlands Aphaenogaster ants make twenty-inch-deep nests occupied by a few hundred workers. New World tropical leafcutter ants create colossal underground metropolises, each housing several million workers that tend huge fungus gardens. Every ant species constructs a nest so distinctive that an entomologist can usually tell which one created it.

Florida's coastal plains are ideal for studying the ants' subterranean architecture: the deep, homogeneous sand is a congenial medium both for the ants and for the researcher seeking a permanent record of these ant cities. After practicing on examples of modest size, I decided to tackle the abandoned dwelling of a particularly ambitious nest-building species: the Florida harvester ant. The nest (pictured opposite) contains 135 chambers arranged along four vertical connecting tunnels that total thirty feet in length. Some of the chambers are specialized for food storage; this nest held about a quarter of a million seeds collected by workers for later consumption. The colony that had built and occupied this nest began with a queen that left her home and mated with another colony's male. After digging a narrow, twelve-inch-deep chamber, she sealed herself inside, laid her first few dozen eggs (a single mating provides the queen with a lifetime supply of sperm), and then reared the hatched larvae and pupae with nutrients stored in her body. These pupae emerged as workers, which then reared more workers, and as the colony grew, the ants deepened the nest and added more chambers. A large harvester ant nest may be as deep as ten feet and contain as many as 200 chambers.

Once or twice a year, the colony abandons its home and excavates a new one—a formidable task that in the case of the nest shown here was completed in four or five days by about 5,000 workers. Together they weighed a total of seven-tenths of an ounce and moved forty-four pounds of sand. Within such nests, the living inhabitants arrange themselves more or less according to their stage of life. Larvae and pupae live in the bottom third, where they grow into young adult workers that will care for the brood of eggs and larvae surrounding them. As the workers grow older, they gradually drift upward, changing their occupation from brood care to more general duties, such as transporting seeds and maintaining the food-storage chambers. Later they take up residence near the surface, where they become the colony's defenders and spend the last quarter of their one-to-two-year lives venturing outside to forage for seeds and insects.

In spring the colony breeds some winged males and unmated queens that will, in time, seek mates outside the colony. During their age-related upward migration, the workers become more and more active in excavating chambers to hold the growing population and its food supply, which is why the nest has a top-heavy shape. The ants' social organization helps shape the space in which they live, and the space in turn organizes the colony by providing separate areas and chambers for various activities and functions. Harvester ant colonies thus have four dimensions—the usual three dimensions of space and the vertical dimension of worker age.

Born during World War II in the Sudetenland region of Czechoslovakia, Waiter R. Tschinkel grew up in Texas, Alabama, and Connecticut. After attending Wesleyan University, he earned his doctorate in biochemistry at the University of California, Berkeley, with a thesis on chemical communication in beetles. He enjoys digging holes and can excavate a hundred cubic feet of earth in about an hour—an avocation that suits his passion for casting ants’ nests in plaster. Tschinkel is currently the Menzel Professor of Biological Science at Florida State University, where for thirty years he has conducted research on how ants manage to function as a superorganism. He has published more than sixty scientific papers on the social biology of ants.

Ant Homes Aphaenogaster rudis is a common woodland ant that builds rather shallow nests housing a few hundred of their elegant, elongated workers. Trachymyrmex septentrionalis is a fungus-gardening ant. Inside its egg-shaped nest chambers, it cultivates fungus gardens made from caterpillar droppings and leaf bits, and is nourished by the gardens’ produce. Odontomachus brunneus, the trap-jawed ant, is a primitive ant that maintains small colonies. Workers skulk around in forest litter with their mandibles wide open. When small creatures touch the trigger hairs between them, the mandibles snap shut with enormous speed and force. Prenolepsis imparis can be found all the way from southern Canada to the mountains of central Mexico. In much of this range, workers are active only during the cool season. Young worker ants are fattened up by their older sisters during the winter. The colony then seals the nest and lives off the stored fat. The next generation is reared beginning in August, and only when these are adults do the ants open the nest again to forage. Photographs of Walter R. Tschinkel and his plaster casts of ant nests by Charles F. Badland, Dept. of Biological Science, Florida State University.

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