Part 9

The Maddening Tarantula

The tarantula of southern Europe—a large, hairy spider—long was credited with causing a weird, infectious madness by its bite.

The first reported effect of its poison—actually quite mild—is said to have been to put the victim into a deep lethargy from which he could be roused only by music which set into motion an overpowering impulse to get up and dance. Once the victim started to dance he could not stop until he fell to the ground from exhaustion. Then the condition supposedly was cured for a year. On the anniversary of the bite, however, the dance was involuntarily repeated. From the tarantula’s first victim the dancing mania allegedly spread like a contagious disease through the surrounding countryside. The name still is used both for an Italian dance and for the music which accompanies it.

The tarantula is a subterranean creature which hibernates in its burrow during the winter. Bees and wasps are said to be killed almost instantly by its bite. The spider always strikes at the junction of the head and thorax.

A Flower That Grows Through Solid Ice

A plant that drills through several inches of solid ice to bloom in early spring is the blue moonwort of the Swiss Alps. It belongs to the primrose family. In autumn it develops thick, leathery leaves. These lie flat on the ground, expectant of the snow and ice sheet that may cover them to a depth of several feet.

When spring arrives and the hot sun melts most of the snow and some of the ice, water trickles down to the rootlets and arouses growth in the sleeping plant. Internal combustion ensues with the floral tissues. The resulting heat melts the ice about the uprising flower buds and the stem pushes its way upward. More water flows to the roots and finally the plant tunnels a passage to the air and sunshine. So long as the heat given off from the growing stem and buds is sufficient to prevent solid freezing of the parts the plant is indifferent to the surrounding ice cold temperature. It undergoes the usual transformations, is fertilized by early bees and forms many hundreds of wonderful blue flower groups which look as if they were beds over a thick layer of transparent ice. The leaves are now no longer thick and fleshy, but thin and papery. They yield up their carbon compounds as fuel to melt a tunnel through the ice and production of buds and blossoms on a flower stem above the ice mantle.

The Versatile Ant Farmers

There are microscopic “farmers” whose fields are measured in fractions of inches. They are ants—the most widespread fungus-growers in the Western Hemisphere. Their range extends from Florida to Brazil. They are tiny creatures, seldom noticed, who cultivate a species of yeast which is their sole food.

The ways of life of this curious ant with the formidable scientific name of cyphomyrmex rimosus minutus, have been studied throughout their habitat by Dr. Neal A. Weber of Swarthmore College.

“The ant,” says Dr. Weber, “is versatile in the American tropics where the humidity is high and the temperatures uniform. The most common sites are in clay soil on the forest floor. An empty snail shell, a curled dead leaf or a rotted twig may suffice for a colony of these small ants or they may find requisite conditions among roots or in the dead wood high in the rain forest canopy.

“During the rainy season in Panama City there was a nest on a concrete cylinder above ground which protected a gas meter. The cylinder was 17 centimeters high (about 6 inches), by 36 centimeters in diameter and was covered loosely by a concrete cover. In the narrow space on the rim under the cover a colony had walled off an elliptical area 36 by 17 millimeters (about 4 inches by 3/4 of an inch), in which the entire nest with a fungus garden was formed. During drier periods the ants would move down into the soil.

“The workers usually are slow-moving and become immobile at the slightest disturbance. Sometimes, however, they run as rapidly as the average ant when disturbed and seek to escape rather than feign death. In “feigning death” the ants quickly curl up their legs and fold their antennae close to the body so that they appear almost invisible bits of dirt when casually examined.

“The ants spend much time in grooming the forelimbs, antennae and other parts of the body. Regardless of how dusty an ant may become momentarily, it keeps its antenna immaculate by drawing it through its mouth and licking and cleansing it. They also clean one another. In grooming each other the ants may carefully go over a large portion of the body. In one instance a slightly callow worker was watched as it groomed another of the same age. The one being groomed turned over on its side, like a dog or a monkey. The grooming of each other and the cleaning of the brood is a vital part of their activities as it removes alien bacteria and fungi and also may have a nutritive function so far as the brood is concerned.

“The fungus garden consist of masses from a quarter millimeter to a half millimeter in diameter (from about 100th to a 60th of an inch.)”

They have their bitter, nearly microscopic enemies. Upon them, as upon elephants, ride much smaller, bareback riding mites whose acrobatic stunts would be the envy of any circus performer.

“Seven out of 16 ants so examined,” Dr. Weber says, “had mites on them. These mites have no difficulty in moving from one site to another on the ants. A transfer of a mite from one ant to another was watched. It had been riding on one ant when another brushed by waving its antennae over the other as is customary. In a flash the mite grabbed the tip of the left antenna. The ant did not attempt to dislodge the mite although it already had two others on its body. The mite had a rough ride, but was not dislodged.”

The peculiar type of fungus grown by the ant does not grow naturally outside the nest. It can be isolated and cultivated but it quickly is overwhelmed by other fungi in any artificial culture. It is probable that ant and fungi need each other for survival. Possibly the saliva of the insect is essential for the growth of the primitive plant. Likewise the peculiarly developed fungus is essential for the well-being, even for the survival, of the ants. It is one of nature’s partnerships.

Ostracoderms: Ancestors of True Fish

The race of fish first appeared about 350,000,000 million years ago in the Silurian geological era. It was made up of grotesque, clumsy, heavily armored animals who crawled over the ooze of the sea bottoms with very little, if any, capacity to rise or propel themselves in the water. The ascent from such an unpropitious beginning to the swift, graceful swimmers of today is one of the wonder stories of evolution.

These Silurian animals were the ostracoderms. They belonged to the general fish complex but were not in the direct ancestral line of any extant fish. This race continued, in various groupings, for at least 150,000,000 years. The earliest forms were wormlike animals whose fossils are found in ancient rocks of Esthonia. Their heads and the forward parts of their bodies were covered with bony plates. They had no fins to serve for steering and balancing. In appearance they were close to tadpoles. It is quite obvious that they were bottom-dwelling forms who swam, if at all, awkwardly and laboriously. The evolution into more and more efficient swimming animals can be traced through later and later fossils throughout the life history of the race. The body became more flexible. There was a gradual reduction in the thickness of the external armor as the ostracoderms came to depend more and more on speed and less on invulnerability. At the end they probably were comparatively good swimmers.

A little later than the earliest of this long extinct family came the first representatives of the true fish—probably derived from the same general ancestral stock. They also were bottom-dwelling animals, although from the beginning they appear to have been a little better adapted for swimming. In these also, the head and forward part of the body were encased in heavy armor. In ostracoderms, however, this had formed a continuous shell, allowing no anterior freedom of motion in the water. In the earliest true fish it was divided into two parts, the head shield and the body shield. For the most part, however, they could use only the tail and posterior part of the body for propulsion. But through many generations various diversifications of the race became more and more fishlike in form, shed their heavy protective plates, developed paired fins for steering and balance, and continuously improved as swimmers.

“We must take it for granted,” explains Prof. Anatol Heintz, Norwegian paleontologist, “that the ancestral forms of the vertebrates evolved in water. Most primitive forms lived on the bottom and had not yet specialized sufficiently to be able to swim. If the oldest vertebrates were bottom-living or burrowing forms they must have learned to swim, just as later they learned to crawl, walk, run and finally fly.”

Among the earliest groups of true fish were the coelacanths, or “hollow spines.” They left many fossil remains over a period of 200,000,000 years. Supposedly they became extinct about sixty million years ago, at the start of the dawn age when most higher life types known at present first appeared. Through all the vast eons of their existence the “hollow spines” changed little.

Three years ago came one of the outstanding events in present day biology. A living coelacanth was caught by native fishermen off the northeastern coast of Madagascar. It was quite similar to its fossil ancestors—armored head and all. Apparently the Madagascan fishermen had been capturing similar creatures in their nets occasionally for years, without realizing that they were of any particular significance.

To biologists the news of this capture was as exciting as would have been that of finding a living dinosaur. The coelacanths, in fact were hoary with age when the earliest dinosaurs appeared on earth. This fish was a survivor from days when animals first were developing spines and brains.

The specimen, however, was practically ruined before it came to the attention of the scientists. Native sailors had sliced it open from snout to tail. All the brain and other soft parts of the head were gone. Other parts were so badly mangled that it was impossible to reconstruct them.

Since then several others have been caught. An intriguing possibility is that of obtaining a female with unborn young. A developing embryo supposedly recapitulates ancestral forms. If one could be found it would be possible to reconstruct something of the real ancestry of the first back-boned animals.