General Articles

DIRTY WORKER

A. C. ANDERSON September 1 1947
General Articles

DIRTY WORKER

A. C. ANDERSON September 1 1947

DIRTY WORKER

A. C. ANDERSON

BENEATH the good Canadian soil, that rich earth with its flourishing crops, its vineyards and its market gardens, there toils unseen and unacclaimed a farmer who has never hitched on overalls or ridden a tractor—the earthworm. He doesn’t ask for a share in the glory of the West, nor is the deaf, blind creature aware of his essential part in the scheme of things. All he knows about, or feels instinctively, is that he must burrow and burrow in the earth, eating what decayed organic matter comes his way and when the mood is upon him uniting with other earthworms to propagate his kind. He will probably continue to do it as long as the world remains.

Ask your neighbor who dug his back garden and

the irate reply will be, ”-----1 did.” When a

man has given up his golf, sweated, cursed, and labored; got his bald head sunburned and nearly broken his back at the work, it is understandable he should want full credit for the garden. But nevertheless the earthworm had a hand in it too. That unappreciated, wriggling, squirming, slimy creature, that women find revolting and men consider only as fish bait, is the gardener’s loyal friend and quite an agriculturalist in his own right.

The annual blistering of hands on a garden fork results from the unwelcome knowdedge that turning the soil is necessary for plant growth. The earth is thereby aerated, finely divided, brought to the surface where rain and sun can reach it, and the fertilizing organic material is plowed under for delicate plant roots to draw in as food. But all of this is precisely what the earthworm does.

We work in the garden because our wives insist upon it, but the earthworm lives there and does not limit himself to occasional evenings or a Sunday

afternoon. He labors unceasingly, like a good fairy with a tiny magic shovel, and by his accumulated effort he makes as brave a showing as we do with our fine, store-bought equipment.

Simple and Home Loving

IN SPITE of its important place in nature’s plan the earthworm is one of the simplest of animals. It belongs to an extensive family of segmented worms called the Oligochaeta, and although 1,800 earth-burrowing species are known, the two or three common ones are those that turn up in fields and gardens everywhere. From Labrador and the Maritimes, through Quebec and Ontario, out across the prairies to British Columbia they are known variously as the Dew Worm, Morning Crawler, Earth Wriggler, Fishworm or almost any other name that might suggest itself. But always we have in mind that long-bodied, gooey pinkish-brown fellow' that we’ve dug for and fished with since we were kids.

Although blind, the earthworm can distinguish between strong light and no light at all. In the protecting darkness of the night it forages for decayed leaves and other such matter but it locates

them by touch and rarely leaves its burrow entirely, always keeping a portion of its body within the hole. It knows instinctively that a blind worm’s place is in the home, especially when the outside world deals just as harshly with earthworms as it does with humans. When dawn appears the busy nightworker senses the light even although it cannot see the grey of the sky, and retires to the security of its cavern and the solitary life that knows few enemies. Sometimes it will ignore the voice of caution and lie close to the surface, usually in the gathering dusk of twilight, but if a hungry bird is about it pays for the indiscretion with its life. Such is the law of nature.

Continued on page 48

Continued from page 21

Among the earthworms there is no such thing as a family group. If it did exist it would pose the question of who was the poppa and who the momma, because these earth dwellers are completely bisexual. Each worm possesses a functional set of male and female organs, and though self-fertilization is impossible a pair can fertilize each other at the same time. The act of pairing takes place at night, on the surface. If uninterrupted each worm allows most of its body to project from its own burrow, still keeping a portion of its length w'ithin the hole, and they press their belly surfaces together in an amorous embrace that resembles a pair of gremlins popping up from adjacent holes to shake hands.

About once a week the breeding worms will deposit whitish, small cocoons at or near the surface, and these will hatch a fortnight later. Each cocoon may contain from one to 10 embryo worms and since breeding continues through the warmer months without interruption, the resulting progeny is quite sufficient to meet the demands of fishermen, moles, birds, chickens, and small boys who dig them up just for fun. These cocoons are secreted from the swollen, prominent

section of the worm’s body near the head end. This section is known as the clitellum and is a sign of sexual maturity.

People who have left a mark on the world, from Archimedes to Thomas Edison, attribute much of their success to persistence, and this is also the earthworm formula. In the beginning he got off to a bad start by choosing an absurd way to cultivate the land— he burrows by eating the soil—but he offsets his inefficiency by working longer hours. His mouth, if we can use that term for a cavity that is toothless, boneless and soft as meringue, takes in soil granules by a sucking action. In his little gizzard they are ground to powder and are finally voided in the form of small pellets known as castings. These are deposited partly in the burrow but the bulk are carried to the surface, and in this way the subsurface soil is being constantly brought to the top. It provides a fresh facing of the rich mold so highly prized by gardeners and in this miracle of replenishing the soil every finely divided particle has passed through the body of a worm. Not only that, but the castings are rich in a nitrate form of plant nourishment, so the earthworm thus performs a fertilizing service in addition to his routine magic.

"Ah yes,” you say, rubbing your aching muscles reflectively, "but the

earthworm is very small and my garden is even bigger than it looks.” You are quite right that a single worm, or even a few, would take a long time to turn over a garden or replenish it with plant nutrients. But in cultivated areas of England—and the figures are presumably applicable to some parts of Canada —it has been estimated that the normal earthworm population of the soil will in 10 years provide a new surface layer of rich mold two inches deep. That’s a lot when you recall that every crop is nourished from only a shallow depth of topsoil.

The incredible rate at which worm castings smear a new face on the earth’s surface is of interest to the archaeologist as well as the farmer. Ornaments, weapons, coins and other bric-a-brac of ancient peoples are often dug out of the earth, sometimes a thousand years after the owner himself dropped from sight. The normally vigorous action of rain, sun and air would in a short time erode such articles beyond recognition, for even things as resistant as flint arrowheads will soften if exposed to weathering. They slowly disintegrate to a formless shape and are no longer recognizable as what they were. But worm castings throw a protective covering over anything left on the ground and it is thus shielded from the atmospheric agencies.

Continued on page 50

Continued from page 48

If an object can withstand the mildly erosive action of moist earth it may be uncovered centuries later and contribute another chapter to man’s laboriously compiled history of the ages.

If a particular plot of land does not contain the material suitable for plant nourishment it w ill not be attractive as a homesite for the earthworm. In eating the earth as it makes its burrow the earthworm assimilates some of the soil ingredients as food, and when its favorite dishes, leaves and manure, are not available, it is forced to live entirely on what organic matter it can extract from the soil. Earthworms are then an indication of the soil’s probable fertility. An experienced gardener considers t hat one fat specimen showing up with each throw of the garden fork in autumn is an indication that all will be well with next year’s crop. If the worms are few in number, undernourished and not uniformly distributed, t he gardener feels his soil is lacking in organic food and applies a dressing of manure.

As a very small boy in Scotland I used to dig the worms when we wanted bait for trout. One old farmer, in w'hose field we were, watched us as he stuffed his pipe and rested from his labors. In his canny way he evidently assessed the earthworm at full value and disliked seeing them leave the ground. I can still remember his words. “Dinna tak more than ye can use, laddie,” he said. “An’ ye’ll no be needin’ the verra big worms to catch wee trouties.”

Some authorities now claim that insect sprays and chemical fertilizers, such as the widely used ammonium sulphate, destroy earthworms or drive them from the soil. These new-school agriculturalists feel that natural

manures, coupled with earthworm activity, will eventually prove more valuable than application of chemicals which may show an immediate return in crop yield but which ultimately work against the farmer by disrupting his labor relations with millions of earthworm assistants.

Deaf, Dumb and Blind

The great naturalist, Charles

Darwin, investigated the earthworm with characteristic thoroughness as long as 75 years ago. He kept them in small pots of earth and when studying their habits found them entirely deaf to “shrill notes from a whistle . . . shouts . . . piano . . . and the deepest notes of a bassoon.” After demonstrating that his pets were deaf Darwin subjected them to mechanical oscillations by setting the pots on top of a piano. He discovered they were extremely sensitive to vibration and would withdraw instantly from sight if the pots quivered from a note struck on t he keyboard.

Without this ability to perceive vibrations they would be utterly at the

mercy of any foraging creature that considers tender worms a tasty dish, for it is difficult to imagine anything more defenseless than a deaf, blind creature without claws or teeth, whose sense of smell is practically nil and whose brain power is no great shakes even at its own level of society.

It is perhaps unfair to disparage the worm’s mental equipment, because he does exhibit some intelligence and a slight capacity for learning. He has a pronounced instinct for using leaves to block the entrance to his hole, and the scientific referees credit him with an intelligence score because more often than not he drags in the narrow end of the leaf first. It’s not the sort of intellect that attracts attention at Harvard but in worm circles it’s rated as quite some cunning stuff.

Their ability to learn has been shown by laboratory experiments that simultaneously prove the worm’s talent and man’s ingenuity. A covered-in wooden tunnel, Y-shaped, is fitted at the end of one of its short, arms with a pair of electrodes that will give a slight shock to anything that blunders up that way. The other short branch of the Y leads to a pile of earth and everything the worm recognizes as home. When earthworms are released in the long, straight leg of the Y, some of them crawl up the danger path and an equal number haphazardly get home free. When the same worms are repeatedly released in the straight part of the apparatus they learn in time to avoid the shocks.

The earthworm has a nervous system, an extensive set of blood vessels, and requires oxygen just as we do. In the absence of lungs his respiratory action takes place through the skin and this must at all times be in a moist condition. One of the fastest ways to kill an earthworm is to take it from the damp earth and keep it in a dry atmosphere. For a brief period its own body mechanism can keep the skin moist, but very rapidly it shrivels up and you have a desiccated, tough, dead worm of no interest to fish, bird or man.

After a rainstorm, you’ll usually find a quantity of dead worms on the surface of the soil. Why they die is still pretty much of a scientific guess, but one thing is certain: they don’t drown. Every fisherman knows that earthworms can survive long periods of total immersion. Best theory is that rain water quickly loses its absorbed oxygen as it trickles through the earth and to evade oxygen starvation the worms come to the surface, where, even on a cloudy day, there’s enough ultra-violet light to weaken his sensitive body and eventually kill him.

In one way and another the men in the white lab coats have had quite a run at the earthworm. Among other things they have decided about the little fellow, is that he feels no pain, and if he squirms about after being cut in two, pain has nothing to do with it. Perhaps it’s peevish ill temper. But the logic is in the best scientific tradition.

The proof is this. If one of the common earthworm species is cut in two the front half crawls away while the rear half squirms and twists about alarmingly. The scientist gazes impassively at the two parts of the worm and wags his head gravely. It seems obvious to him that if the front half has taken tfie bisection calmly enough, without unseemly contortions, and granting that both halves of the worm must show equal sensitivity to pain at the point of severance, that the rear half is squirming about, not in pain, but in response to some other unspecified stimulus. With the impartial attitude of mind that distinguishes the scientist from the merely sentimental observer, he states, “We cannot infer pain from the character of a worm’s movements.”

Half Brothers

Examine an earthworm carefully and you will see that its segmented anatomy resembles a stack of miniature inner tubes. By an accordion action it is able to extend and retract itself, and when it does so the rows of hairlike projections on its underside dig themselves in like ski poles to lever the worm along. This way of locomotion sounds just as ridiculous as its method of burrowing, but when danger threatens it can actually scuttle into its hole like a rabbit. The same tiny bristles can be wedged fast against the walls of the burrow when a grim tug of war develops with a hungry bird. Even after a fullgrown robin gets one end of an earthworm in its beak it has to brace both feet and work for its supper.

The segmented structure of an earthworm is partly responsible for the fact that if cut in half it usually does not die. Each half simply regenerates new parts to replace what it lost and we have two, separate, live worms; presumably half brothers. And even more intriguing than that, if one of the new half worms is itself bisected, it is possible under some conditions to produce two, live, whole worms from what was only half a worm in the first place. One of the common earthworm species can have its head cut off up to a maximum of five times and still regenerate a new head for the ones it lost. Of course there is a limit to this multiplying without breeding and small sections will not usually regenerate into whole worms.

No matter how industrialized a country may become, or how far removed from an agricultural economy, its people live simply by someone’s efforts somewhere on the land. The good earth is still our only provider and the earthworm is an indispensable helper. Like a humble slavey in a great mansion the small creature labors its whole life through, with man the gainer by its work. And even in dying it makes a final contribution to our welfare since its decomposing body yields some two per cent of valuable nitrogen to the soil. ^