You should try my game sometime, of identifying the trees in a forest by looking down instead of up. You may be surprised to find that it’s easy to identify trees that way; all the evidence you need is within reach. The forest floor is a through-the-looking-glass reflection of the trees above. Live above, dead below. The dead matter consists of old leaves, needles, flowers, seedpods, and branches shed by the trees. This debris may seem like useless waste until you comprehend the circle of life and realize that without this decaying waste there would be no living forest. The live trees shed their dead parts; these are decomposed by the many living things in the humus: fungi, bacteria, worms, insects; and the nutrients released in that process are available to the trees again. Ever notice that forest trees grow beautifully without anyone fertilizing them? They fertilize themselves with their own rain of debris. It’s that phoenix again: life rising out of the ashes.
Squat down and touch the debris on the forest floor. Feel, in Thoreau’s words, “the solid earth! the actual world! the common sense! Contact! Contact!”1 Look at what this ground layer is composed of; it will probably be different where you are, but in this spot there are a lot of pine needles. Pick up the needles and see that they are about six inches long and in bundles of three needles each— they are from loblolly pines. Look around; you will see some pinecones scattered on the forest floor. The cones will take much longer than the needles to decompose, but they too will eventually be broken down and return their nutrients to the living trees. There will be other things on the forest floor too. What are those small tan, dry, lightweight, comma-shaped things? You may already know that they are the pollen-producing cones from the pine: the “male” cones. They shed their yellow pollen in the early spring and then drop to the ground where they, too, will decompose. In this forest, scattered in among the pine parts, are leaves that were shed in the fall by the forest’s deciduous trees: maple, oak, beech, hickory, gum.
After you have touched and identified the things in the top layer, gently move that layer aside. Beneath the layer of recognizable parts is a darker, damper layer. You can still see pine needles, but they are not in bundles anymore, they are in little bits and pieces. You can recognize pieces as once part of a leaf, but the type of leaf can no longer be identified. You will probably see white strands of fungus living on the energy still contained in the bits of plant parts, and you will see little “roly-poly” bugs and worms and ants and snails; and you should know that there are many, many organisms in this layer too tiny to see with the naked eye. It is in this decomposing layer, so often overlooked, where the majority of the species in a forest live. The forest’s real biodiversity lies here, but because these organisms are so small and “unsexy,” they are less studied and thus are not as well understood as the larger organisms like the trees, the birds, and the mammals.
But a true naturalist will eventually try to learn about them. Rilke says in his poem from A Book for the Hours of Prayer:
I live my life in growing orbits
which move out over the things of the world.
Perhaps I can never achieve the last,
but that will be my attempt.
I am circling around God, around the ancient tower,
and I have been circling for a thousand years,
and I still don’t know if I am a falcon, or a storm,
or a great song.2
Or, he might have added, a snail. Among the many forest organisms that need further study are the little land snails. There may be dozens of species of them in a single location, some smaller than a freckle and others larger than a quarter, but all with the characteristic whorled shell we associate with snails. The slugs and snails you find in gardens near houses are usually species that have been introduced from other continents; here in North America, removed from their native predators, they often become pests. But the snails you will find in the forest are native, and many of the species have very small ranges. It is quite possible that the tiny snail you are looking at today lives only in one corner of your state and nowhere else on the planet.
The soft body of a snail consists of a head connected to a large, fleshy foot. In the snail’s mouth is a tongue that resembles the blade of a chain saw. With this hard, raspy tongue, or radula, snails eat just about anything they can find on the forest floor: fungi, soil microorganisms, insect eggs, and plants, both living and dead. Particular snail species probably have different food preferences, but we have that much information for only a few snails.
Eat and be eaten is the first law of nature. The forest snail populations are kept in check by the frogs, salamanders, turtles, small rodents, and birds that eat them. Although often overlooked, the snails are an important part of the forest food chain.
Examine a snail closely and you will see that it has two pairs of tentacles: the shorter pair, toward the front of the head, is used to explore the world by touch and smell; the larger pair is topped by the eyes. The eyes can be retracted down inside the tentacles if the snail is threatened—by something such as the light touch of a human fingertip. So the little snail goes crawling through the moist forest litter touching, smelling, looking, eating. A specialized structure at the edge of the shell opening secretes calcium carbonate, adding to the shell, increasing the size of the whorl and therefore the size of the snail. “I live my life in growing orbits …”
When conditions are dry, the snail pulls its head and foot into the shell and closes the opening with a flat piece of shell that has grown onto the foot for this specific purpose. Some snails have been known to stay in this “dry hibernation” for years.
I have already mentioned that many—most—plants have flowers with both male and female structures, but did you know that some animals also have both male and female parts? Snails are neither male nor female—they are both: simultaneous hermaphrodites. When conditions are right, a solitary snail can mate with any other snail it encounters. We are used to thinking of sexual organs as being at the opposite end of an organism from the head, but the snail’s genital opening is located in its cheek. If snails can be said to have cheeks. When two snails mate, both give and receive sperm through this opening. Each fertilized snail will then head its separate way to find a moist spot to lay his/her eggs. The eggs are laid in clusters that look like tiny pearls. The baby snail within each egg absorbs the calcium in the outer layer of the egg and uses it to build its shell. When the baby snails hatch, the pattern of their whorls is already established; the number of whorls will never increase, just the size of each individual whorl.
NOW LOOK DEEPER. There is another layer, another organism whose genes have miraculously survived nature’s unpredictable dice game. Another organism threatened by the destruction of its habitat. A small, shiny, reddish-brown fly (Oidematops ferrugineus) lives in the forest. It is late May, the weather at last is dependably warm, and the fly, a female, has just hatched. She will fly through the forest for a few days before she finds a mate. If she is lucky and finds a suitable mate, the pair will copulate for up to an hour. The day after they part ways she will begin to lay her eggs. She will lay ten to thirty eggs a day, depositing them singly on tufts of moss on the damp forest floor. She may live for up to three weeks, a long time as insect lives are counted, and she will continue laying eggs until she dies, leaving behind hundreds of eggs whose fate she will never know.3
If conditions in the forest are right, the eggs will hatch about a week after they are laid. The tiny wormlike larvae immediately begin to crawl across the forest floor. Each larva will crawl and crawl until it either dies, is eaten, or encounters a snail of the species Stenotrema hirsutum. Only that snail species will do, but fortunately it is one of the more common ones.
The little larva crawls into the snail’s shell and positions itself between the shell and the fleshy body, with the tip of its tail end protruding so it can “breathe” through the hollow tube evolved for that purpose. Many, many things can go wrong, but if all goes right the larva will begin feeding— on the snail. For the first six days the snail doesn’t seem to be affected by the little larva tearing off and consuming bits of its flesh. But during this time the larva is getting bigger and bigger and removing more flesh with each bite. After a week the dying snail will retract into its shell; a few days later, trembling, it will die.
After its host’s death the now plump larva has a last large meal before casting the smelly leftovers out of the shell, which has now become the exclusive home of the fly larva. The shell offers the larva plenty of room to construct a pupal case in preparation for its transformation into a fly. The pupa will stay in the snail shell throughout the long winter. When May’s warmth reaches the forest floor the fly will emerge from the pupal case and the cycle will continue. Although the fly’s method of making a living may seem cruel, only a minuscule percentage of larvae are able to complete their life cycle successfully.
IF YOU USE YOUR HANDS to dig deeper through this decomposing layer of the forest floor you will appreciate how thick it is, and how toward the bottom there is no longer anything recognizable; the plant parts that make up the rich humus of this bottom layer fell from trees years ago. After digging down six inches or more you will reach the mineral soil layer. In a healthy forest this soil layer will almost always be cool and damp. That is just the way tree roots like it. A healthy forest isn’t possible without the thick decomposition layer to insulate and feed the roots and seedlings (and the fungi they associate with).
WHAT BECOMES of the snail shell once the fly has emerged from its pupal case? In time, of course, it too will decompose and nourish the trees, but another use may be made of it first. A small organism that looks like a tick with miniature lobster claws has been hiding in the shell. The organism is a pseudoscorpion, and just like a lobster or a crab—its seagoing relatives— it must shed its hard protective layer in order to grow. Unlike a snail that can grow steadily larger, the pseudoscorpion must go through two molts to reach adulthood. During molting it is soft-bodied and vulnerable, and the snail’s empty shell offers a refuge. At least that is the conjecture of the scientists who found the little insects inside snail shells.4 Or perhaps the pseudoscorpions were merely seeking protection from excessive heat, cold, or desiccation.
The pseudoscorpion cannot stay in the snail shell for his entire life; he must leave the shell to eat, reproduce, and travel. When he is outside the shell he is a part of the life on the forest floor. He feeds on other forest floor organisms, mostly on insects smaller than he is, such as mites, which he grabs with his pincers. A duct in the tip of the each pincer releases venom into the unlucky prey.
There are many species of pseudoscorpions, and feeding, nesting, and mating behaviors vary between them. We know very little about the behavioral ecology of most species. The anatomy of an organism— its size, its shape, what it looks like— is almost always the first thing scientists discern; behavior patterns generally come later. The reason we know so much about anatomy is that an organism doesn’t have to be alive for us to determine its structure; in fact, it is easier if the organism is dead. The live ones move around too much. That’s why John James Audubon shot the birds he wanted to study. Even plants can “move” too much for the convenience of botanists, changing, as they do, with the seasons. So “specimens” are “collected” (killed) and pressed between sheets of paper for further study.
An examination of the anatomy of the specimen allows the biologist to determine if it is a new species or not. If it is a new species a Latin name will be given to the dead thing. After the description and the naming, the next easiest thing to determine about an organism is its distribution: where else on the planet it occurs. Living or dead specimens work equally well for this study. But to learn what a thing eats or how it mates or how and when it moves through the landscape, you need to study living creatures. It is hard work; and we have so much left to learn.
We do know about the mating behavior of a few species of pseudoscorpions. We know, for instance, that the males fight one another for the right to mate with females, and usually the male with the largest pincers wins. The winner deposits a packet of sperm on the ground, and either the female smells it and takes it into her body or the male maneuvers her into place over it and assists her in retrieving it.5
The female pseudoscorpion has appendages that can produce silk, much as a spider does. She spins a small, round silken nest, lays her eggs in it, and attaches it to her body. There seems to be no end to the ingenuity of nature. I was amazed to learn that the female pseudoscorpion actually passes a nutritive fluid directly from her body to the developing embryos in the silken sack. An insect that breast feeds!
Pseudoscorpions can live for two or three years, an extraordinary life span for an insect. They have been found on the bark of trees, living in the nests of birds and mice, under stones in the soil, and in empty snail shells, of course; I wouldn’t be at all surprised if we found them in sweet gum balls.
But what if the habitat becomes unsuitable or the food runs out? If that happens, the pseudoscorpion simply boards a flight to a better place. A pseudoscorpion can be transported long distances by grabbing onto a fly or a beetle. If the pseudoscorpion is lucky, in-flight meals will be served in the form of mites that live under the wing covers of beetles. Perhaps the beetle is happy to give a ride in exchange for the elimination of some of its parasites.
The snail, the fly, the pseudoscorpion: if the trees did not drop their organic matter to the forest floor, none of them could live here. When I attempt to understand just a small sample of the life on the forest floor I can relate to the custom of Jain monks, who go barefoot and tread lightly on the earth to prevent the unnecessary killing of living creatures. Their practice may not be practical here, where the holly and the sweet gum grow, but perhaps shoes are an acceptable compromise between the tender touch of a bare foot and the crushing jaws of logging machinery.
… because everything here is so much, and everything
seems to need us in this fleeting world, and
strangely speaks to us. Us, the most fleeting. Once
for everything, only once. Once and no more. And we, too,
only once. Never again. But to have been here,
this once, if only this once:
to have been of the earth seems irrevocable. (11–17)
I am grateful to have been here.