Just Out From Under A Rock

On that May morning the fragrance of wild honeysuckle floated up out of the swamp. I had walked a wooded slope where birds swarmed in the oaks and maples, and insects and spiders, dazzling in their numbers, were in every green bush. Suddenly I tripped on a stone and knelt down to turn it over. One of my college professors had taught me a long time ago that some of the most fascinating things often lay hidden beneath a rock.

As I lifted the stone, I saw a sudden seething and boiling of tiny black ants. I had uncovered their nest and, as the light fell upon them, each seized a tiny white object in its jaws—a pupa, or unborn ant—and rushed wildly about with it. I had unroofed their fortress, and now they seemed not to care for their own safety, only for that of their unborn young.

These were Tapinoma (Tapinoma sessile) ants. I once found a colony of them nesting in the bottom of a bird's nest in a swamp—they are not at all particular about their nesting places. The Tapinoma may have from 2,000 to 5,000 individuals in each of its colonies (some species have only a few hundred). It nests from sea level to the highest mountain-tops, in the soil, under bark, in places with or without a covering object, and up to 200 females (an unusually large number in an ant colony) may be in the nest.

Tapinoma ants are gentle and inoffensive, and sometimes nest peaceably with other ants, yet they can defend themselves well. I touched one of them and a strong odor, of rancid butter or of overripe coconuts, arose from the nest. Some of the ants had discharged butyric acid from their bodies, a secretion they use when they are attacked. The sticky fluid, squirted on other ants, is usually fatal to the attackers.

It may take months or even years for a rock to settle and accumulate enough moisture to provide a home for the many tiny creatures of the earth. But wherever the rock is—in woods, field or garden—the animals of darkness will find a haven under it.

My garden, like all gardens, is a lovely place. I remember at one time that the flagstone walk there had been merely something to tread upon. Now each stone plays a part in a new game—a kind of animal treasure hunt of mine. Of all the strange animals that live beneath stones, none fascinates me more than our remarkable sow bugs, or pillbugs. They are slate-gray, about half an inch long, with sharply scalloped edges. Some people call them wood lice, but they are more of the sea than the forest, being related to crabs and lobsters. They resemble armadillos, are clad in a jointed armor of chitin (pronounced kightin) and also live under boards and logs where they eat decaying plants and wood. Because of their gill-breathing organs, which must be kept moist, they live mostly in damp places.

Under my flagstones I sometimes find them in the hot dryness of summer, drawn together in groups. In their desperate need, they have learned that closely huddled together like honeybees and earthworms they can conserve their precious moisture. Bunched, either in winter or summer, their respiration rate is lowered—which helps lessen the harsh effects of temperature changes. When they can touch each other they keep quiet and thus economize their bodily energy.

Like the kangaroo of Australia and our own American opossum, the young of sow bugs develop in a brood pouch, or marsupium, on the underside of the female's body. When they emerge they look exactly like their parents. And, like opossums, they feign death by curling up in a tight ball.

About 35 years ago a naturalist in Chicago discovered that in autumn some sow bugs travel deep into the earth in tunnels of mound-building ants and hibernate with them in their nests.

One of our neighbors, who had no sheltering stones or pieces of wood lying in his garden, became fascinated by the story of our sow bugs and how they live. I told him of the 52 kinds that had been described by scientists in North America. Of these, nine species had never been seen again after their original capture and description many years ago. Then I showed him how to capture sow bugs by digging a circular hole or tunnel in a raw potato. He buried it in the dead leaves under his dogwood tree and next morning had caught 36.