Part 3

Standing from three to four feet high and looking and acting deceptively like a human being, the emperor penguin undoubtedly is one of the most remarkable birds in existence. It presumably is confined to the Ross Sea side of the Antarctic continent. The bird—actually it is about two-thirds feathers—remains an evolutionary enigma. Theories have been advanced that it is the last surviving member of the fauna of the Antarctic continent about fifty million years ago when the shorelines were free of ice. It certainly is off any known road of evolution.

The Strategy of Warrior Ants

Total war is the way of life for army ants. The picturesque, devastating drives of their vast hordes have nothing whatever to do with exhaustion of food or anything of the sort. The wars come in fixed cycles, regardless of supplies.

There are two species of these ants on Barro Colorado Island in the Panama Canal Zone. Each species has approximately 50 colonies and each colony consists of from a few hundred thousands to more than a million individuals. At the head of each colony is a single queen who lays all the eggs.

There is a new lot of larvae every 33 days—all workers or incompletely developed females. Development is restricted by the amount of food available. Since each brood consists of about 60,000 individuals, a colony theoretically might reach titanic proportions. However, it does little more than maintain its population. The death rate of soldier ants, in constant combat, is very heavy.

Once each year, at the start of the dry season in the tropics, a colony queen produces a sexual brood of about 3,000 males and six queens. The rest of the 60,000 eggs laid at this time are incapable of hatching and are fed to the new-born sexed individuals. They apparently have some of the nutritious properties of the royal jelly fed to queen bees.

This sexual brood is produced in what has been called a statory period in which the army maintains a fixed bivouac for about three weeks. During this time the new queens develop and around at least one of them a new group of workers, about half the whole, tends to congregate. A strange antagonism seems to develop between the old and new groups. Eventually the colony divides in two and each half starts moving in opposite directions. The other new queens are lost in the shuffle.

Most of the newly developed males are ‘excess baggage.’ During the winged, or mating, stage they fly into the forest where the great majority of them are eaten by birds. When the surviving ants light on a tree, on the ground or on some other object, the wings drop off. Then they apparently wander about aimlessly until they come to an army ant trail which they recognize by the odor and follow it until they come to the colony which has made it. If this happens to be a colony of their own relatives, they probably are killed by the workers. If it happens to be an entirely foreign colony, they may be accepted. This apparently is one of nature’s mechanisms for intruding new genes into a strain.

The raiding activities of a colony are carried out during the day from a central headquarters. During the daytime raiding individuals return to the colony from their forays and by dusk all have returned. At night the bivouac is changed, the whole colony moving forward along one of the trails blazed by the raiders. A new headquarters is thus established. A colony moves from six to seven hours before striking a new bivouac. Not infrequently, if no promising site is found, it moves from dusk to dawn.

This would seem like constant activity, too strenuous even for the constitution of an army ant. Actually the individual workers probably get plenty of rest. Each colony is divided into two units—the raiders and those that constitute the structural unit. The walls of the “headquarters” are made up of the bodies of the latter. These “living brick” do nothing throughout the day. They may be asleep. When the raiders return at dusk the structural unit breaks up and the members lead the migration to a new bivouac. The erstwhile raiders follow leisurely in the rear and in turn become the structural unit when a stopping place is selected.

When to rest? When to raid? There apparently is an irresistible war rhythm, like the rhythm of the tides, in the basic constitution of these ants. Some have postulated the same sort of thing, on a lesser scale, in man who goes to war every so often but camouflages the war tide with economic or political explanations.

These ants are remarkable not only as warriors but as architects. They build complex, air-conditioned, hanging houses out of thousands of their own suspended bodies. Within these structures the queen is sheltered, eggs laid, young hatched and reared. Much of the time the “houses” are constructed anew each night.

This home-building behavior is unique in nature, as Dr. T. C. Schneirla of the American Museum of Natural History has pointed out:

“Without any active excavating and without any manipulating of fallen materials, colonies of these species form a domicile with their own bodies. A typical bivouac is a cylindrical mass hanging from the underside of some projecting surface to the ground. In addition to the sides or under-surface of logs, other typical places are the spaces between gut tressed tree roots, masses of brush, undercut banks of stream beds, or the overhanging edge of a rock.

“The characteristic ability to cluster their bodies, as well as the manner of clustering, depends first of all upon an anatomical characteristic—the opposed, recurved hooks on the terminal tarsal segments of the workers’ legs. The first ants to settle in a new place catch into a rough or soft surface by means of the tarsal hooks, or rather are pushed into this anchored position as newcomers run upon them as they stand and stretch them out in a hanging position. In fact, the hooks are really anchored by the added weight of others that have crawled down over the body of the first ant, fixing it in place and soon immobilizing it.

“In the nomadic phase a new bivouac is formed at the end of each day of raiding. In the advanced and most complicated stages of raiding in the afternoon, caches of booty tend to be formed at each busy junction of raiding trails, increasing in size as more and more ants are knocked around and forced out of traffic. As darkness comes and raiding ceases such clusters grow. Several hanging clusters start from elevated ceilings. As each new cluster begins, the initial slender hanging threads may become ropes which extend to the ground. As the ropes continue to grow they are joined together into a single columnar mass.

“At first this mass is small in diameter, but as more and more ants pour into it the wall spreads outwards from the center and so a symmetrical cylinder results.”

In the tropical environment of the army ants some sort of air conditioning is necessary for comfortable living—perhaps, with this particular species, for any living at all. It has been well developed during the more than 50 million years the insects have been on earth. Says Dr. Schneirla:

“The interior of the bivouac, where the brood is sheltered and the single colony queen rests, offers an impressively stable environment to these more susceptible members of the community as well as a central resting place for the worker population. The hanging cluster traps a cubic area for atmosphere which does not reach the extremes of temperature and dryness attained by the general forest environment, but in general is somewhat warmer and more humid at night and somewhat cooler and dryer during the day.

“This result is achieved mainly as a result of worker behavior. Workers cluster more closely together at night in reaction to the lower temperature of the forest at the time. The bivouac walls become tighter and thus better conserve heat produced internally by the brood.

“Conversely, after dawn, when increasing light excites growing numbers of ants to leave the bivouac, as the raid grows, this wall thins out, usually develops small apertures, and is undercut at the bottom. The effect is to increase internal air circulation as well as to cool the atmosphere of the interior through evaporation, so that the internal temperature of the bivouac does not rise to the height reached at midday in the environs.

“The incubation properties of the bivouac represent an important factor in echelon life, for with less regular atmospheric conditions in the nest the stages of brood development could not have their typical regularity in timing.”

Uganda’s Miniature Dinosaur

A grotesque creature abundant in the Kishasha Valley of Uganda is the three-horned chameleon. It grows to a length exceeding twelve inches and the males look like miniature versions of the ancient dinosaur monster, triceratops. Three curious horns, an inch to an inch-and-a-half in length, protrude from the nose and between the eyes of males.

These are extremely pugnacious animals; they use their horns in fights to the finish. At times the contests develop into prolonged pushing matches with the horns interlocked, but a really vigorous fighter can dispose of an adversary in a few minutes. African natives are terrified of these demoniacal-looking little animals.

The Strange Ways of Spiders

“With other classes of animals, and even with plants, man feels a certain kinship—but spiders are not of his world. Their strange habits, ethics and psychology seem to belong to some other planet where conditions are more monstrous, more active, more insane, more atrocious, more infernal than on our own. Frightfulness and ruthlessness appear a part of their nature and we stand appalled when it dawns upon us that they are far better armed and equipped for their life work than we for ours.”

Thus writes Dr. W. E. Stafford, U. S. Department of Agriculture naturalist. There probably is quite general agreement with his sentiments. One chills at the picture of some other planet where spiders and their kin who have evolved minds equal to that of humans are the dominant animals.