Two of the most beautiful of these shell forms were recently discovered by Dr. Paul Bartsch, former Smithsonian curator of mollusks. Fragile, translucent, colored as delicately as the loveliest of orchids, these particular snails are the fairies of the mollusk world in the unconscious artistry with which they have constructed their moving palaces. One, a hitherto unknown species, has a remarkable combination of pale orange, orange buff, deeper orange and flame color—all shading delicately into each other. The color effect is such as one might find rarely in rose petals. Another has a blending of ivory, olive green, lemon yellow and orange.
Termites That Eat Lead
On Barro Colorado island in the Panama Canal Zone the Smithsonian Institution maintains an “experimental cemetery.” It consists of rows of upright posts which look like gravestones, half buried in the soil. The purpose is to test the propensities of the island’s 42 species of termites—just about man’s most persistent and expensive enemy in the tropics—to eat different kinds of wood impregnated with different kinds of repellants and poisons. To date approximately 35,000 tests have been made. The longer the work is continued the more Dr. James Zetek, former director of the station, is impressed with the contrariness and ingenuity of the blind, ant-like insects which achieve sub-human acmes of engineering ability, and whose appetites are marvelous.
Among Barro Colorado’s termites are some extraordinary bugs indeed. One, for example, eats lead. It gnaws its way through the lead sheathings on cables. This is not because it likes a lead diet. Lead, in fact, is indigestible and the insects starve to death. But their appetites are so insatiable that the little creatures just keep on gnawing, in the hope that there will be wood on the other side.
This particular insect is known by the scientific name of coptotermes niger. It has been known to eat through a concrete floor nearly five inches thick—again not because of any particular liking for concrete but because of the expectation of coming eventually to digestible wood. The feat was made possible because the sand used in making the concrete contained many fragments of sea shells which were dissolved by a powerful chemical excreted by the insects.
It is very difficult to dispose of termites by poison—that is, permanently. Races have risen here, for example, which seem to thrive on arsenic. The insect lives on the cellulose in wood. This must be digested by certain intestinal bacteria in the digestive tract. If these microörganisms can be poisoned the termite starves. At first at least 99 percent of the bacteria succumb to heavy doses of arsenic. This means that 99 percent of the termites are killed. But always there are a few exceptionally tough bacteria with a high resistance to the poison. Their descendants in a few generations apparently become almost entirely resistant. With their help a new race of termites comes into existence.
Ordinarily termites attack only dead or dying wood. Some of them, however, carry fungi around with them to kill their own wood. The Canal Zone insects can dispose of living trees. Dr. Zetek tells of one attempt to establish an avocado plantation. He warned against it. When the trees had reached the fruit-bearing stage and seemed healthy he was ridiculed for his warnings. Branches were heavy with avocados and there was promise of a record crop. He shook his head when shown the flourishing orchard. “The poor trees,” he remarked. “They know they are going to die. They are just making one last mighty effort to preserve their species by producing plenty of fruit and seeds.” He secured the orchard owner’s permission to chop down one tree. The whole inside, he found, was riddled with termite galleries. This tree and all the others in the orchard were dead within a year.
The Plant That Eats Animals
There are life-and-death battles in the microscopic world between tiny shelled animals and flesh-devouring fungi. The phenomenon can be compared to that of a tree catching and eating big turtles.
When a culture of diseased plant roots is made, there soon appear great numbers of microscopic plants and animals—bacteria, fungi, amoebae, nematodes and other life forms. Immediately the struggle for survival starts. The animals try to eat the plants and the plants attempt to devour the animals.