Oddities of the Insect World

Edwin Way Teale.

Nineteen centuries ago, when Pliny the Elder was writing his natural history in Rome, men believed that insects were creatures without blood, that butterfly eggs were drops of solidified dew, that echoes killed honey bees, and that gold was mined in the mountains north of India by a giant ant "the color of a cat and as large as an Egyptian wolf."

"This gold," Pliny assured his readers, "is extracted in the winter and is taken by the Indians during the heats of summer while the ants are compelled by the excessive warmth to hide themselves in their holes. Still, however, on being aroused by catching the scent of the Indians, they sally forth and frequently tear them to pieces, though provided with the swiftest camels for the purpose of flight, so great is their fleetness, combined with their ferocity and their passion for gold."

Today, nobody credits Pliny's story of wolf -size ants with a passion for gold any more than they believe in his oriental locusts that grew to such size that their hind legs were dried and used for saws. These traveler's tales, the product of imagination or misunderstanding, have been long discredited. Imaginary wonders, in fact, are less needed in dealing with the insects than with any other group of living creatures. The truth is odd and dramatic enough.

In 1857, when Alfred Russel Wallace landed on the Kei Islands of the Malay Archipelago to collect natural-history specimens, he soon noticed that each time he entered a deep damp forest glade he found the air filled with a fragrance that reminded him of attar of roses. For a long time he tried to trace the perfume to flowers. Finally he discovered that its source was not a flower but a beetle, the green and purple and yellow tiger beetle, Therates labiatus. It inhabited the damp and gloomy glades and fed mainly on insects that visited the flowers. Its perfume, Wallace concluded, aided it in attracting small nectar gatherers to the spot.

At least three species of oriental praying mantids use color instead of perfume to aid them in securing their food. These insects, like the mantid native to the southern part of the United States, imprison their prey within the spined traps formed by their forelegs. By having parts of their bodies expanded into thin plates which are brightly tinted on the under side, the oriental insects resemble flowers on the bushes where they hunt. When climbing to a favorable position, the mantid keeps the bright-colored under sides of the plates hidden. However, when it finds itself among flowers to its liking, it turns the colored plates uppermost and remains motionless until a victim alights close by.

One British naturalist reports seeing a mantid in India climb laboriously to the tips of three branches before it found flowers in bloom. On the first two times, when it found buds, it slowly retraced its steps and began again. Attaining the flowers, it took its position among them and exposed the under side of its pink, petallike plates. Some oriental mantids have plates that are blue, some mauve, some purple. Still others have pure white plates, that have a surface that is glistening and waxy, like the petals of real flowers.

In a number of instances, the orthoptera of the Tropics are ingeniously camouflaged by nature to escape the notice of their enemies. For example, the long-horned grasshopper, Metaprosagoga insignis, possesses wings which not only resemble leaves but which are equipped with irregular patches that look as though the leaf tissue had been eaten away by an insect, leaving only a network of veins visible. Another tropical leaf-grasshopper has brownish wings that suggest dried leaves. The resemblance is heightened by the fact that markings near their extremities give the impression that they are cracked or torn. Then there is a mantid of the Orient, Brancsikia aeroplane, which has curled-up brownish edges to its wings, thus heightening their resemblance to dry brown leaves. On the wings of a katydid from Venezuela, which William Beebe once showed me, imitation dewdrops and fungus spots increased the effectiveness of the insect's camouflage.

Probably the most famous camouflaged insect in the world is Kallima, the dead-leaf butterfly of the Far East. In The Malay Archipelago, Alfred Russel Wallace tells of his first meeting with this remarkable butterfly. At the time he encountered it he was collecting in Sumatra, beating the bushes for insects and examining his net carefully for poisonous snakes, which were often dislodged from the branches, before extracting the insects he had caught.

"When on the wing," he writes of the dead-leaf butterfly, "it is very conspicuous. The species is not uncommon in dry woods and thickets and I often endeavored to catch it without success, for, after flying a short distance, it would enter a bush among dry or dead leaves and however carefully I crept up to the spot where the butterfly settled and though I lost sight of it for some time, I at length discovered that it was close before my eyes but that in its position of repose it so closely resembled a dead leaf attached to a twig as almost certainly to deceive the eye even when gazing full upon it.

"A very closely allied species, Kallima inachis, inhabits India where it is very common. No two are alike but all the variations correspond to those of dead leaves. Every tint of yellow, ash, brown, and red is found here and in many specimens there occur patches and spots formed of small black dots, so closely resembling the way in which minute fungi grow on leaves that it is almost impossible at first not to believe that fungi have grown on the butterflies themselves!"

Walkingstick insects, in the Tropics, also present some amazingly realistic instances of insect camouflage. One of the most remarkable bears the scientific name of Achrioptera spinosissima. About half a foot in length, its green and brown body is decorated with spines that are tinted bright red like thorns. The insect looks for all the world like a broken piece of briar moving along on six legs. Another tropical walkingstick, Palophus reyi, is almost a foot long. The outer skin of its body is roughened into an amazingly close approximation of dry bark on a dead twig.

Such resemblances benefit the insect by making it inconspicuous amid its surroundings. But what benefit those brownie bugs of the insect world, the Membracidae, obtain from the fantastic adornments they possess is often difficult to see. Again, it is in the Tropics that the most spectacular examples are found. Nature seems to have run riot, designing oddities just for the sake of originality. In some species of treehoppers, the prothorax is drawn out into hornlike adornments; in others, it rises in a high, curving crown; in others, it forms spears or balls. Oftentimes these are brightly colored. While American treehoppers are less extravagantly formed than those in the Tropics, some species are among our oddest-appearing insects. All are small, and the strangeness of their forms frequently is unappreciated without the aid of a magnifying glass.

When Charles Darwin was crossing the Atlantic in 1832, at the start of his famous voyage in the Beagle, the ship dropped anchor at desolate St. Paul's Island, 540 miles from the coast of South America. "Not a single plant," Darwin writes, "not even a lichen, grows on this islet; yet it is inhabited by several insects and spiders." Most of them were parasites on the boobies and other sea birds that landed on the barren rocks and one was a small brown moth belonging to a genus that feeds on feathers.

The bleak cluster of volcanic rocks that form St. Paul's Island is but one of many strange places where insects are able to survive. Oceanic water striders skate over the waves hundreds of miles from shore. They lay their eggs on floating sea-bird feathers and other bits of refuse and often live their whole lives without ever seeing land. In Ecuador, butterflies are found among the crags of the Andes 16,500 feet above sea level, while explorers, scaling the flanks of the Himalayas, have encountered a praying mantid almost as high.

Snow-white and blind insects live deep beneath the earth's surface in caverns. Springtails skip across snowbanks during February thaws in Northern States. Certain flies breed in the brine of the Great Salt Lake and a number of insects make their homes in the dangerous confines of insectivorous pitcher plants. One curious little larva spends its early days swimming about in pools of petroleum, breathing through a tiny tube which it thrusts above the surface. And another insect is able to live in the mud of hot springs where the water reaches a temperature of 120 F.

At the opposite extreme is the so-called ice-bug, or alpine rock crawler, which inhabits cold mountain recesses, usually at elevations from 5,400 to 8,600 feet above sea level. It prefers temperatures of about 38 F., temperatures at which most insects are dormant. If the mercury rises to 80 , the ice-bug seems to suffer heat prostration.

Two insects that spend their early days under curious conditions are familiar to most parts of the United States. They are the rat-tailed maggot and the froghopper, the immature form of the Cercopidae. The former inhabits stagnant water, caught in knotholes, or other waste fluids. It feeds on the bottom and breathes air through an extensible tube that forms its tail. Thus, like a diver obtaining oxygen through an air hose while working on sea bottom, the fly larva is able to remain submerged as long as it desires.

By surrounding itself with bubbles, the little froghopper produces its own climate. In spring and summer, small masses of froth often appear on grass stems and weeds. They are the foam castles of the cercopids. A kind of bicycle pump, formed of overlapping plates beneath its abdomen, which provide a chamber into which air is drawn and expelled, permits the insect to produce bubbles in excess sap, which it has sucked from the plant. Within this bubble mass, sheltered from the direct rays of the sun and kept moist by the foam, the immature insect spends its early days. For millions of years, it has been employing its own primitive form of air conditioning.

One of the classic studies of the French entomologist, J. Henri Fabre, concerned the aerial journey of the wingless larva of the oil-beetle. Hatching from eggs deposited by the female insect close to flowering plants, the minute larvae slowly ascend the stems and lurk among the petals until a wild bee alights in search of pollen or nectar. Quickly the young beetle attaches itself to the hair on the bee's back and goes sailing through the air as a passenger when the winged insect flies back to its nest. Here the larva lets go. It has found its proper home, a place where it will be supplied with ample food until it transforms into an adult beetle. Not all larvae attach themselves to the right insects, but enough do to carry on the species by means of this ingenious stratagem.