FLOWERS (Part 2 of 2)

Avoiding Self-Pollination

Self-pollination, transfer of pollen from the stamen of a flower to the pistil of the same flower, as distinguished from cross-pollination.

A few kinds of flowers are self-pollinating; that is, they can be fertilized with their own pollen. In most cases, however, nature takes great care to prevent self-pollination. Cross-pollination usually produces more vigorous plants. This requires the transfer of pollen from one plant to the stigma of another plant of the same species.

Flowers avoid self-pollination in several ways. In some cases the stamens and pistils mature at different times. In other flowers the stamens are shorter than the pistils and hence do not deposit pollen on their own stigma. Wind-pollinated flowers usually bear the stamens and pistils in separate flowers. Alders, birches, walnuts, and hickories bear catkins with pistillate flowers on some branches and catkins with staminate flowers on other branches. Corn has the pistils and stamens on different parts of the same plant. The tassel bears the staminate flowers; the ear bears the pistillate flowers. These are known as monoecious (of the same household) plants. A few trees, such as cottonwoods and willows, carry the separation even further, with the staminate flowers on one tree and the pistillate on another. These are known as dioecious (of two households) plants.

How Fruit Develops

After fertilization of the ovule has taken place the petals, sepals, stamens, and usually the upper part of the pistil fall off. Now, as the ovules grow into seeds (embryo plants), the ovary, or seed case, also changes. In some plants it turns into a fleshy covering, called fruit. The ovary wall separates into two layers. The inner layer becomes a hard shell, called a stone, or pit, which encloses the seed. The outer layer forms the pulpy portion of the fruit. The peach, plum, cherry, and apricot are examples. In the case of berries the entire ovary becomes a fleshy mass in which the seeds are embedded. In the apple, pear, and quince, the ovary and its seeds become the core of the fruit. The pulpy part, which is eaten, is the modified calyx.

The ovaries of many plants develop into so-called dry fruits capsules, pods, nuts, and acorns. Like the fruits and berries, they protect the seeds and help scatter them when they are mature. Another kind of dry fruit is the achene. In this case the ovary wall becomes a coating of the single seed. It does not open at maturity, as the pods and capsules do, to release the seed. Achenes are developed by flowers that produce but one ovule, such as the individual flowers of the composites. The style of the pistil sometimes remains attached to the achene as a long, feathery tail that carries the seed away on the wind. The most common flower with seeds that are readily scattered by the wind is the dandelion, regarded by most people as a weed.

The Origin of Flowers

At least 250,000 species of flowering plants are known. All of them descend from a primitive ancestor that no longer exists. The most primitive modern flowers are the members of the buttercup order, Ranales. A step higher is the rose order, Rosales.

The simplest flowers are the least skilful in making seed. Many stamens mean a great deal of pollen is wasted. A large number of pistils means that many will fail to become pollinated and produce seed. All members of the buttercup order, which includes the little buttercup itself and the splendid magnolia and water lilies, and all the roses have many pistils and stamens. The most highly specialized and most successful flowers are the composites.

Two Kinds of Flowering Plants

Angiosperms (or Angiospermae), class of flowering, vascular plants of the division Magnoliophyta having seeds in an enclosed ovary.

Flowering plants belong to the phylum Tracheophyta, or vascular plants. Thus far the flowers and seed making up only one group of this phylum, the angiosperms, have been described. These are flowers that enclose their seeds within an ovary.

Another group of flowering plants, called gymnosperms, has naked, or exposed, seeds. These plants include the conifers, or cone-bearing trees, such as the pine, fir, spruce, cypress, and cedar. Cones take the place of flowers.

Cones are of two kinds staminate and pistillate. They are usually borne on different branches of the same tree. The staminate, pollen-producing cones are small and last only a few weeks in the spring of the year. The pistillate cones are the large familiar ones. The ovules, usually two in number, are located on the upper surface of each scale. The ovule consists of an embryo sac surrounded by a covering that later becomes the seed coat. In the covering is a tiny opening called the micropyle (little gate).

In late spring the pistillate cones stand upright with the scales opened wide to catch the windblown pollen. When pollen lodges between the scales, they close. Thus protected within the closed cone, the pollen sends out a pollen tube that enters the ovule through the micropyle. When the seeds in the cone are fully grown, it again opens, releasing the matured seed. All gymnosperms are wind-pollinated.

BUTTERFLIES AND MOTHS (Part 1 of 2)

DEFINITIONS:

BUTTERFLY: 1 any of various families of lepidopteran insects active in the daytime, having a sucking mouth part, slender body, rope like, knobed antennae, and four broad, usually brightly coloured, membranous wings 2 a person, esp. a woman, thought of as flitting about like a butterfly and being frivolous, fickle, etc. 3 a) short for BUTTERFLY STROKE b) a contest in which each contestant uses a butterfly stroke.

MOTH: 1 any of various families of four-winged, chiefly night-flying lepidopteran insects, similar to the butterflies but generally smaller, less brightly coloured, and not having the antennae knobed.

Lepidoptera, the order of scaly-winged insects including butterflies, moths, and skippers.

To a poet butterflies and moths are like fluttering flowers. Scientists know them as a group of insects that make up the order Lepidoptera, meaning "scale wings." They are so named because their wings and certain portions of their bodies are covered with a fine dust.

Under a microscope the dust is seen to be made up of millions of finely ridged scales that are arranged in overlapping rows. Each scale has a tiny "stem" that fits into a cup like socket. The beautiful colours and markings of the insect are due to the scales, which come in a remarkable variety of colours.

Butterflies and moths look very much alike. The best way to tell them apart is to examine their antennae, or feelers. Butterfly antennae are slender and the ends are rounded into little clubs or knobs. Moth antennae lack these knobs. Many of them look like tiny feathers, and some are threadlike.

Most butterflies fly and feed during the daytime. Moths fly at night. Butterflies rest with their wings held upright over their backs, and moths with their wings outspread. These are not safe rules to follow, however, for some moths are lovers of sunshine and some fold their wings. The honours for beautiful colouration are about evenly divided. The pale green luna moth and the rich reddish brown cecropia moth are as handsome as any of their gay cousins.

Different kinds of butterflies and moths live throughout the world in temperate regions, high in snowy mountains, in deserts, and in hot, steamy jungles. They vary in size from the great Atlas moth of India, which is 10 inches from tip to tip of the spread wings, to the Golden Pygmy of Great Britain, which is only 1/5 inch across. In North America north of Mexico there are 8,000 kinds of moths, but only 700 kinds of butterflies.

Like all insects, the butterflies and moths have three pairs of legs and a body that is divided into three sections head, thorax, and abdomen. On the thorax, or middle section of the body, are two pairs of wings. The pair in front are usually the larger. The scales on the wings contain a pigment that gives the insect some of its colour.

Certain colours, however, and the iridescent shimmer come from the fine ridges on the scales. The ridges break up the light into the various colours of the spectrum. The beautiful blues, for example, are due to the way in which the light strikes the scales.

These insects feed on the nectar of flowers and on other plant liquids. The mouth is a long slender sucking tube. When it is not in use it is coiled up like a delicate watch spring. By uncoiling the tube, the insect probes deep into the flowers and sucks up the nectar. Some kinds of insects have spines on the tip of the tube that tear the plant tissues of ripe fruits and start the juices flowing. Certain kinds have imperfectly developed mouth parts and do not feed at all. Soon after they become adult insects they mate, lay their eggs, and then die.

As the adults visit the flowers in search of nectar, they rub against the stamens and pistils, and so help in the process of pollination. The pronuba moth that pollinates the desert yucca is particularly interesting in this respect.

The Life Cycle Metamorphosis

Butterflies and moths go through a life history known as complete metamorphosis. (The word means "change of form.") The female lays many eggs. From these hatch tiny larvae called caterpillars. At this time of their lives they become pests, devouring the food plants of man. The female always lays its eggs on the kind of plant that the caterpillars will use for food.

After several moults (skin shedding) the full-grown caterpillar is ready to turn into a pupa. At this stage the butterflies and the moths differ. Butterflies spin a button of silk that adheres to a twig, leaf, or other solid support. They then cling to the button by a sharp spine at the end of the body and moult for the last time. As the old caterpillar skin peels off, there appears a naked pupa called a chrysalis. It is an "insect in the making," encased in a tough, flexible shell.

Cocoon, envelope, often largely of silk, which an insect larva forms around itself.

Some moth caterpillars spin silken cases called cocoons inside which they pass the pupal stage. Others burrow into the ground, about six inches below the surface. There the caterpillar moults for the last time. The pupa is covered with a hard, dark, sticky substance that protects it from cold and moisture and from attacks of other insects.

The time spent in the chrysalis or cocoon varies with the kind of insect and with the time of year. It may be weeks or months. The pupa does not appear to be alive, but marvellous changes are taking place. Most of the organs and other tissues of the caterpillar break down, turning into a semi liquid.

From this material are formed the wings, legs, and other parts of the adult. At last the adult is ready to leave the pupa case. If it is an earth-burrowing kind, the pupa, before it opens, is raised to the surface by means of thrashing movements of the insect on the inside. After the insect has freed itself it is wet and its wings are soft and limp. It slowly fans the wings to pump air into the veins. Gradually the wings expand and harden. In a few hours the adult is ready to fly and to seek a mate. Most adults live from four to six weeks. Some live only a few days, some can live as long as ten months.

Enemies and Defences

Butterflies and moths have many enemies. Birds are among the worst. Various kinds of flies and wasps lay their eggs on or in the bodies of the caterpillars, so the larvae dig in and feed on the tissues.

Sphinx moth (or hawk moth), any of the order Lepidoptera, family Sphingidae; especially the tomato-worm sphinx (Protoparce quinquemaculata); moths are excellent pollinators of plants.

Both caterpillars and adults have ways of defending themselves. Stinging hairs and spines that may be poisonous protect some caterpillars. The woolly bear caterpillars are covered with a fuzz that makes them an unpleasant mouthful. "Frightfulness" is a defence of quite harmless creatures, such as the hickory horned devil with its red horns, the ugly tomato worm, and the caterpillar of the sphinx moth.

Monarch butterfly, insect (Danaus plexippus) of the order Lepidoptera, family Danaidae; breeds on milkweeds.

The monarch butterfly has a foul taste and odour that birds have learned to avoid. The tasty little viceroy butterfly looks exactly like the monarch, only smaller, and for this reason is also avoided by birds. In addition, many butterflies and moths at rest resemble dead leaves or the twigs and bark of trees.

BUTTERFLIES AND MOTHS (Part 2 of 2)

How the Winter Is Passed

Moths and butterflies may spend the winter in any stage of their lives. Bag worms hibernate as eggs. The eggs are in cocoon like silken bags about two inches long, hung from the tips of branches. Gypsy moths winter as eggs attached in masses to a piece of wood and covered with scales from the female's body. Viceroy butterflies winter as caterpillars inside a nest made of a rolled leaf fastened to a twig. The caterpillars of the Baltimore butterfly spin a silken tent on top of their food plant and pass the winter within it. The cat tail moth winters as a caterpillar inside cat tail stalks. The codling caterpillar burrows into an apple, and the corn borer caterpillar spends the winter burrowed into an old cornstalk.

Pupae are well protected from winter cold by silken cocoons or hard, thick cases. The cecropia, promethea, and polyphemus moths winter in their cocoons. The red admiral butterfly hibernates as an adult in hollow logs. The adult mourning cloak butterfly seeks any shelter available.

Although the majority of these insects pass the winter in a resting state, some migrate southward. Great numbers of monarch butterflies are seen flying in the autumn. Some scientists believe that these are dispersal movements or simply a scattering of large populations. There is little evidence of a return flight to the north, except possibly by a few battered individuals. The next year's population is built up chiefly by monarchs that remained in the northern climate through the winter.

Butterflies and Moths as a Hobby

Monarch butterfly, insect (Danaus plexippus) of the order Lepidoptera, family Danaidae; breeds on milkweeds.

Making a collection of butterflies and moths, carefully mounted and accurately labelled, is a fine hobby. It is interesting to raise these insects from eggs and observe their life history.

The abundant monarch butterfly is a good species to start with. Any weedy field with milkweed growing in it is a good place to find eggs and caterpillars. They are to be found on the underside of the leaves.

Do not disturb the eggs or the caterpillar, but pick the plant to which they are attached.

Place the plant in a can filled with water to keep the milkweed fresh. Wire such as florists use will hold the weed upright. As the milkweed begins to wither, replace it with a fresh leafy stalk, and let the caterpillar crawl onto it. Monarchs will not eat anything but milkweed, so do not experiment with some other plant.

After five moults the caterpillar reaches a length of about 2 inches and is ready to pupate. Care must be taken to prevent its escape. In nature it will leave the milkweed and crawl to some high support. Strip off the lower leaves of the plant so that they do not form a bridge across the can. The can and the plant also may be covered with a wire screen.

On a rib or stem of the plant or on the screen itself, the caterpillar begins to spin its silk button. Through a magnifying glass the silk can be seen issuing from spinnerets in the head. When the button is completed, the caterpillar turns around, attaches the hooks at the end of its body to the silk, and then gradually releases its hold until it is hanging free, upside down. Several hours elapse. When the long antennae at the head end become limp and shrivelled, the caterpillar is ready to turn into a pupa. Some time before the old skin is ready to split open, the caterpillar begins to swing and jerk. Suddenly at the top of the head the skin opens, and with thrashing movements the insect rolls it up toward the silk button. What is revealed is a beautiful case of jade green studded with golden dots. The pupa case twitches for about two hours, meanwhile shrinking in size. Finally it becomes still. Pupation is completed.

In about two weeks the pupa begins to turn dark. When it is black and transparent, the case opens and the butterfly pulls itself free. For breeding monarchs, the adult must be confined to a cage and provided with a mate. It must have sugared water for nourishment and more milkweed on which the female may lay its eggs. If set free, it can migrate, perhaps thousands of miles, with others of its kind.

Moths as Pests

Adult butterflies and moths do no economic damage. The caterpillars of most butterflies are also harmless. Moth caterpillars, however, cause enormous losses in food plants, fruit, forest and shade trees, clothing, and household goods. Most are better known as "worms" than they are as adult moths.

The clothes moths have infested many households. Two kinds are common. The case-making moth (Tinea pellionella) is so called because the caterpillar spins a shelter case of silk and bits of the material on which it is feeding. The webbing clothes moth (Tineola biselliella), the most abundant and injurious species, spins silky webs as it moves over a piece of material. A third kind, the tapestry moth (Trichophaga tapetezella), is rare in the United States.

The adult moths, or millers, as they are often called, are probably harmless. The clothes moth stays in dark places and flies very little. The adult has imperfect mouth parts It does not feed at all and so does no direct harm to fabric. The female begins to lay eggs, however, before it is a day old, and lays about 100 in the 7 to 14 days of its life.

The soft, white eggs are laid loosely upon the nap of the material on which the larvae are to feed. They are easily dislodged and crushed, so that anything that is regularly brushed or shaken does not become moth infested. In warm weather the eggs hatch in from four to eight days. In colder weather, hatching may take as long as three weeks.

The larvae eat furiously for about 40 days before turning into pupae. The pupa stage lasts eight to ten days in warm weather, and three to four weeks in the winter in a heated building. Eggs, larvae, and pupae die quickly at low temperatures.

Scientific Classification

Scientists divide the order Lepidoptera (scale wings) into two suborders, Rhopalocera, the butterflies, and Heterocera, the moths. The ending -cera means "horn" and refers to the antennae. Rhopalocera means "club-shaped antennae." Heterocera means "otherwise-shaped antennae."

The butterflies are divided into the Hesperioidea, or skippers, and the Papilionoidea, or true butterflies. The skippers are so named because of the erratic way they dart about close to the ground. They are seldom more than 1 1/2 inches across the wings. Their antennae are thickened at the ends with a short hooked tip but not knobed.

At rest the fore wings are held vertically while the hind ones are extended horizontally. The body is stout, like the moths. The pupa state is spent in an incomplete cocoon made of leaves fastened together and lined with silk.

Swallowtail butterfly, large butterfly recognized by tail like extension on hind wings; about 20 species in North America n. of Mexico; black swallowtail (Papilio polyxenes), wings black with yellow and orange spots; tiger swallowtail (Papilio glaucus), wings yellow with black bars and yellow spots.

Cabbage butterfly (or white butterfly), insect (Pieris rapae) of the order Lepidoptera, family Pieridae; its larva is a pest on cabbage and cauliflower.

The true butterflies are divided into several families. The Papilionidae include the swallowtails, largest of the American butterflies. The family Pieridae includes the only butterflies injurious to plants. The cabbage butterfly was introduced from Europe in the 19th century. Its larva is a serious pest.

The Nymphalidae, also called brush-footed butterflies, have small, useless, brushlike front feet, usually carried folded against the body. Best known in this family is the monarch butterfly.

In the family Lycaenidae are the small, brightly coloured blues, coppers, and hair streaks The family Riosinidae comprises the metal marks, most of them southern and western species.

The Heterocera, or moths, are also divided into many families. The giant silkworm moths (Saturnidae) include the oriental silkworm and the lovely luna, cecropia, promethea, and polyphemus moths. The large hawk moths, also called sphinx moths (Sphingidae), are often mistaken for hummingbirds. They are about the same size and hover above flowers in the same way. Unlike most moths, they fly about in sunlight.

PEST CONTROL

1869: Birth of ecology. Most people are unaware that the subdivision of biology called ecology is over a century old. Over the course of its development, ecology has emerged as one of the most significant and studied aspects of biology. Ecology refers to the overall interrelated system of nature and the interdependence of all living things.

The word ecology has been popularized more recently because of the many environmental concerns that have been raised since the 1970s. But as a word, ecology was coined in about 1869 by a German zoologist named Ernst Haeckel. A researcher in evolution and a strong supporter of Charles Darwin's theories, Haeckel spent most of his career teaching at the University of Jena.

The study of ecology dates back to the ancient Greek philosophers. An associate of Aristotle named Theophrastus first described the relationships between organisms and their environment. Today the field of ecology has expanded beyond narrow biological studies to include environmental pollution, population growth, and food supplies.

Organisms considered harmful to humans or their interests are called pests. They include plants or animals that carry disease, cause disease, or destroy crops or structures. The definition of a pest is subjective. An ecologist would not necessarily consider a leaf-eating caterpillar on a corn plant a pest, but a farmer might. The term pest may refer to insects, viruses, and bacteria that carry or cause disease. It may also refer to organisms that destroy crops or man-made structures. Plants, such as weeds or fungi, and vertebrates, such as rats, mice, and birds, are sometimes called pests when they destroy crops or stored foods.

The elimination of pests or the inhibition of their reproduction, development, or migration is known as pest control. The control of pests has a great influence on the world economy.

Even with current pest-control measures, agricultural pests are responsible for the annual destruction of millions of acres of crops worldwide. In South east Asia, rodents have been known to destroy as much as 50 percent of a rice crop before it is harvested. In the United States, over 500 million dollars are lost annually to insect and rodent infestation of stored foods and grains.

Some insects are considered pests because they are wood-eaters. They are a threat to wooden structures houses and other buildings, trees, and fences. Several species of ants, bees, and beetles can also damage wooden structures.

In the field of agriculture, pest control is used to protect farm crops and forests that are harvested for their wood. Pest control has also contributed to the management of many health-threatening diseases, including plague, encephalitis, yellow fever, malaria, and typhus.

Chemical Control

The most common method of pest control is the use of pesticides chemicals that either kill pests or inhibit their development. Pesticides are often classified according to the pest they are intended to control. For example, insecticides are used to control insects; herbicides to control plants; fungicides, fungi; rodenticides, rodents; avicides, birds; and bactericides to control bacteria. Pesticides also include chemosterilants and growth regulators, which are used to interfere with the normal reproduction or development of the pest.

Pyrethrum, old genus of composite family which botanists now place in genus Chrysanthemum; most garden varieties were derived from Chrysanthemum roseum, or Pyrethrum roseum, a handsome perennial with finely dissected leaves and white to crimson and lilac flowers; the flowers of Chrysanthemum cinerariaefolium, used in insecticides, had important part in U.S. troops' fight against malaria-carrying mosquitoes in World War II.

Chemical control of pests probably began with poisonous plant compounds. In the 18th and 19th centuries, farmers ground up certain plants that were toxic to insects or rodents plants such as chrysanthemums or tobacco. The plant "soup" was then applied directly to either the crops or the pests. Chemists later discovered that they could extract the toxic compounds from these poisonous plants and apply the compounds as liquid sprays. Such chemicals as nicotine, petroleum, coal tar, creosote, turpentine, and pyrethrum (obtained from a type of chrysanthemum) were eventually extracted for use as sprays. Organic compounds such as these were eventually replaced by more effective inorganic chemicals, including arsenic, lime, sulphur, strychnine, and cyanide.

With the advent of synthetic organic compounds during World War II, a dramatic change occurred in pest control. The discovery of the insecticidal properties of the synthetic compounds DDT (dichlorodiphenyltrichloroethane) which was widely used against disease-spreading insects during the war and BHC (benzene hexachloride) made the notion of pest-free crops realistic. The development of another synthetic organic compound, the selective herbicide 2,4-D (2,4-dichlorophenoxyacetic acid), led to the development of other selective herbicides.

With the discovery of DDT, 2,4-D, and BHC, researchers began to develop other synthetic organic pesticides, especially growth regulators, chemosterilants, pyrethroids (compounds with insecticidal properties similar to those of pyrethrum), and organophosphate chemicals. This research expanded in order to develop other, non chemical, methods of pest control after the harmful persistence of pesticides in the environment was recognized. It was discovered in the 1950s that DDT and its related compounds are not easily broken down in the environment. DDT's high stability leads to its accumulation in insects that constitute the diet of other animals. These high levels of DDT have toxic effects on animals, especially certain birds and fishes. Scientists also found that many species of insects rapidly develop populations that are resistant to the pesticide.

By the 1960s, the value of DDT as an insecticide had decreased, and in the 1970s severe restrictions were imposed on its use. In the United States, the Federal Environmental Pesticide Control Act of 1972 and the Federal Insecticide, Fungicide, and Rodenticide Act passed in 1972 required pesticide manufacturers to conduct scientific tests on the biological activity, defectiveness, persistence, and toxicity of any new pesticide before the chemical could be marketed. In the late 1980s, the average cost to develop and register a pesticide product was 10 million dollars. In the 1960s and 1970s, public objections were raised over the indiscriminate use of pesticides. The Environmental Protection Agency (EPA) was created in 1970 to ascertain past damage and possible future damage that could occur to the environment as the result of widespread pesticide use, and to set up programs to combat environmental problems.

An alternative concept of integrated pest management was adopted for many agricultural pests. This approach involves non-chemical pest-control methods, including crop exclusion, crop rotation, sanitation, and biological control. These methods augment other pest control programs designed to minimize pesticide usage.

Biological Control

The biological control of pests involves exposing them to predators or parasites. The use of predators and parasites is usually accompanied by a program in which pest-damaged fields are scouted and pest population estimates are made. Predators and parasites are then released by the millions to assure control of the target pest.

China (or People's Republic of China), country in e. Asia; area 3,692,000 sq mi (9,561,000 sq km); cap. Beijing; pop. 1,165,888,000. Circa 1995.

Biological pest control was used by the ancient Chinese, who used predacious ants to control plant-eating insects. In 1776, predators were recommended for the control of bedbugs. The modern era of biological pest control began in 1888, when the vedalia beetle was imported from Australia to California to control the cottony-cushion scale insect. This biological control project saved the citrus-fruit industry.

Insect predators also have been used to control the bean beetle, tomato horn worms, and aphids. Another biological method is the use of bacteria against grubs, or insect larvae. For example, the bacterium Bacillus thuringiensis is used to control the caterpillar larvae of the gypsy moth, as well as the larvae of mosquitoes In the 1980s, mosquito-eating fish and nematodes that prey on such soil insects as corn root worms were introduced as biological-control agents.

Since the 18th century, the breeding of host plants for pest resistance also has been used to control pests. Wheat has been the object of the most extensive plant-resistance research. Effective wheat-breeding programs have led to the development of new wheat varieties that are resistant to rusts various parasitic fungi that infect the leaves and stems of the plant. Corn breeding has resulted in varieties resistant to other fungal diseases, including smut and leaf blight. The classic example of this plant-resistance approach to pest control was the control of phylloxera, insects that attacked the root stock of the European wine grape and almost completely ruined the European wine industry. The problem was solved by grafting the European plants onto the resistant American wine grape root stock.

The development of insect predators to control structural pests has met with little success. Nematodes have been used against termites in laboratories, but field tests have not been successful. Parasitic wasps used against various cockroach species have also been unsuccessful in the field.

Other Controls

Cultural control methods are used to alter the pest's environment and thereby reduce access to breeding areas, food, and shelter. Cultural methods have been used to control the yellow-fever mosquito, which breeds in swamps and small pools of water. With the draining of swamps and the elimination of stagnant pools and other containers where water accumulates, the number of potential breeding places for the pest is reduced. Cultural control has also been used against structural pests, which depend on protected places such as cracks in side walks, roads, or buildings; garbage; and weeds for survival. Structural pests are often effectively deterred when openings to potential hiding places are sealed and debris and refuse are eliminated.

Crops are sometimes protected from harmful pests through diverse planting techniques.

Crop rotation, for example, prevents the development of fungus and bacterium populations. Open-area planting relies on the wind to hinder flies and other insects that damage vegetable crops.

Physical or mechanical control methods are effective against some pests. Such controls include sticky barriers, heat killing (for storage pests), and flooding (for ground pests).

Pressure-treated wood is protected against many wood-damaging fungi and insects. Traps are another mechanical method of pest control. Some traps are designed to either kill or capture rodents and other vertebrate pests. Netting and metal shields are used to keep birds from damaging fruit crops or from roosting on buildings. Electrical light traps attract insects and electrocute them. In some buildings, fans are installed above doors to prevent the entry of flying insects.

An area of pest-control research that has received much attention in recent years involves baiting traps with the pest's own sex attractants, or pheromones. Pheromone traps have been used extensively against the fruit fly and gypsy moth. Pheromones are also being used to attract and trap pests that infest stored foods and grains.

Many countries use importation and quarantine regulations to control the importation of foreign plant or insect pests. Fruit is especially prone to insect infestation and disease. In the United States, the Animal and Plant Health Inspection Service monitors incoming products and materials and requires certain products to be treated prior to entry. Similar controls exist in other countries. Some regions have quarantine regulations to ensure that certain insect pests are not brought into the area. In the United States, individual states have their own inspection services. Some states even have border inspection stations to prevent unauthorized transport of plants across state lines.

Assisted by George W. Rambo.

MANTIS

DEFINITION: any of an order (Mantodea) of slender, elongated insects that feed on other insects and grasp their prey with stout, spiny forelegs often held up together as if praying.

The predatory mantis is well adapted for catching the living insects on which it feeds. It is often called the praying mantis because of the way it holds its prehensile front legs while waiting to make a kill. The mantis remains motionless or sways gently back and forth, with head raised and front legs outstretched in an apparent attitude of praying.

The lively colouration of the mantis may serve as camouflage or as a lure. It lies in wait among leaves while its large compound eyes search for prey. To better blend with its surroundings, it sometimes spreads its wings like a skirt. When an insect appears, the spiny forelegs jerk out to seize the victim. The prey is caught by the sharp, curved hooks at the end of the mantis's legs and is held firmly by the rows of spines. Within about one twentieth of a second from the time the mantis has spied its prey, it has retracted its front legs and is feeding on its catch. Although mantises hunt primarily insects, some larger species can overcome small vertebrates such as lizards, frogs, and young birds.

Mantises often devour one another, and it is common for the female to consume the male after, or even during, mating. The female then lays her eggs in a frothy mass, which, when dry, becomes a brownish, papery case. The mantis lives in tropical regions and also in temperate parts of the world. Many scientists classify it in the Dictyoptera order with cockroaches. They call the suborder Mantida from the Greek mantis, meaning "diviner" or "prophet." Some scientists place the mantis in the separate order Mantodea. Its popular names include mule killer, soothsayer, and devil's horse.

About 1,500 species are known. The most widespread in Europe and North America is Mantis religiosa. M. religiosa and Tenodera aridifolia sinensis were introduced into North America. The latter is often called Chinese mantis. It is native to many parts of Eastern Asia and is the largest mantis in North America. It grows up to 4 inches (10 centimetres) in length.

CORN (Part 1 of 2)

5000 BC: Cultivation of maize. The primary grain in use in North America prior to the European discovery was maize, now called corn in some countries. It was probably grown first by the inhabitants of Mexico. After the arrival of Europeans in the Americas, corn was sent to many parts of the world and is in use nearly everywhere today, often as feed grain for animals.

Maize is unique from other grains in that botanists do not know how the plant evolved. In the Old World, no evidence exists of maize in archaeological remains, and no mention of it is made in ancient writings. It is believed to have evolved solely in the Western Hemisphere.

In the United States, Canada, and Australia the term corn refers to maize, or what is sometimes known as Indian corn. The rest of the world calls this grain maize. (This grain is known in South Africa, however, as mealies.) In England the word corn refers to wheat, and in Scotland and Ireland it refers to oats. This article uses the word corn to refer to maize.

Upon returning from the New World, Christopher Columbus and other explorers introduced corn into Europe, where it was previously unknown. Since that time corn has spread into all areas of the world suitable to its cultivation. Corn was served at the first Thanksgiving Day feast in America in 1621. In modern times, it has become a popular snack for movie viewers in the form of popcorn.

After wheat and rice, farmers the world over use more land for corn than for any other grain crop. More than 319 million acres (129 million hectares) of corn are planted worldwide each year. Most of the corn grown is the coarser kind called field corn. It is not grown for people to eat. Farmers feed it to pigs, cattle, and other livestock. Out of every 100 bushels grown, farmers store half in silos or in bins for feeding livestock. For this reason the value of the corn crop cannot be measured by what is sold as grain. Most of the yearly crop "goes to market on four legs" as pigs and cattle. Thus a large part of the multi billion-dollar corn harvest never reaches the grain market.

Where Corn Grows Throughout the World

Out of every four bushels of corn grown in the world, farmers in the United States produce one. Many states grow corn. Most of it, however, is raised in the famous Corn Belt. This vast fertile region extends across the north-central plains from western Ohio to eastern Nebraska. The top-ranking corn-producing states are Iowa, Illinois, Nebraska, Minnesota, Indiana, and Wisconsin. Corn will grow wherever it has suitable soil, freedom from frost and cold nights, and plenty of hot sun when it is maturing. It also needs ample soil moisture during the hot season.

These conditions are also found in much of Central and South America, around the Mediterranean, in India, and in South Africa. The largest producers of corn, after the United States, are China and Brazil. Other large corn-producing countries are Mexico, India, Indonesia, South Africa, and the Philippines.

An Obscure Ancestry

Some botanists believe that members of the amaranth, or tassel flower, family may have been the wild ancestors of the corn plant. But even in the time of Columbus, corn could not fertilize itself, as do most wild plants or recent descendants of wild plants. The greatest weakness lay in the way corn produces its seed. The top of the stalk has a many-spiked tassel which grows pollen. The plant also has ears with filaments called silks which receive pollen. But the ears are completely wrapped with leaves, and the ends of the silks protrude only from the tips. Therefore the silks cannot get ample pollen unless the plants have many neighbours, as they do in a cultivated field. Botanists think that the plants could hardly survive in the wild state. Corn was apparently unknown in ancient times in the Old World. No evidence of it has ever been found in archaeological remains. There is no reference to it in the Bible or other ancient literature or in primitive art. The word corn in the Bible refers to wheat, not the American maize.

In the New World, however, all the principal types of corn that scientists recognize today were already in existence and under cultivation when the first explorers arrived. The wild ancestor of corn probably came from the Western Hemisphere.

Some botanists think the plant may be descended from teosinte, a grass that grows wild in Mexico and Guatemala. Another theory is that it originated in South America from a primitive pod corn which was also a popcorn. Pod corn kernels are enclosed in pods or chaffy shells. Such a wild corn has not been found.

Ancient Corn in New Mexico

In 1948, scientists of the Peabody Museum, Harvard University, discovered ancient corn in a cave in central New Mexico. The lowest levels of the cave floor contained primitive husks and kernels estimated to be 4,000 years old. This corn bore no relationship to teosinte, but it did have the characteristics of pod popcorn.

In upper and more recent deposits the scientists found corn that appeared to have been crossed with teosinte. Modern corn may therefore be a hybrid of teosinte and wild species which no longer exist, but the mystery is still unsolved.

The Corn Plant and Its Seed

The corn plant is a large member of the grass family (Gramineae). It has a fibrous, woody stalk that may grow to be from 6 to 20 feet high. At the top is its spiked tassel. This part produces the male flowers of the plant. Farther down, the stalk grows one or more spikes which develop into ears. Each one grows out from beneath the base of a leaf, and at first it is completely wrapped in leaves. The spikes bear threadlike filaments (silk) which are the female flowers. Each filament grows from a germ on the spike called an ovule.

The ovules are arranged in rows along the spikes. Each one will produce a seed, or kernel, if the filament of silk is fertilized by a pollen grain. To catch pollen, the green, tender tips of silk protrude from the top of the leafy wrapping around the spike.

All these parts appear after the stalk and leaves are well grown and the plant is receiving plenty of summer sunshine. When the flower parts develop, farmers say that the corn is tasselling out. Soon the tassels produce yellowish dust like grains of pollen. Each grain of pollen contains two sperms.

How Fertilization Takes Place

Now summer breezes gently shake the pollen-laden tassels, and billions of the tiny, sperm-bearing pollen grains jar loose. The wind carries them to the silk of neighbouring plants.

Tiny receivers, called stigmas, at the ends of the silks, catch the pollen. Promptly the pollen grains send tubes growing down through the silks to the ovules. Then the sperm cells pass down the tubes and fertilize the ovules. Thereupon the spike grows into a large, pithy structure called a cob, while the ovules grow and ripen into seeds (kernels).

The growing seeds are made up of a soft yellow hull filled with milky liquid. Corn at this stage is in the milk. The milk has a sweet flavour, and field corn in the milk stage may be used as roasting ears. When field corn is ripe, the kernels are hard, firm, and starchy.

Sweet-corn kernels do not get as hard.

Colours of Corn

When the first European settlers came to America, they found corn with different coloured kernels. The Indians liked particular colours for certain purposes and tried to grow them.

The pioneers preferred the yellow kind for field corn. About 1779 sweet corn was discovered in Pennsylvania. Gradually farmers began to save seed from desirable plants for planting the following year.

CORN (Part 2 of 2)

How Experimenters Developed Hybrid Corn

In 1905 George H. Shull and Edward M. East began developing new kinds of corn by placing pollen from one desirable strain of corn onto the silks of another strain. The process produced cross-bred strains called hybrid corn. After World War I, Henry A. Wallace (who became secretary of agriculture in 1933) and Lester Pfister began hybridizing experiments. By 1926 they had made hybrid pollinization completely workable.

The hybrid plants are remarkable growers. They commonly grow to be 18 or 20 feet tall; some have grown as high as 28 feet. A more important factor is that they have added millions of dollars to the income of corn farmers.

Before farmers had hybrid corn, an average acre of corn yielded 30 bushels. But farmers had to spend the money they received for 25 bushels to pay their costs for each acre planted, leaving only 5 bushels an acre for profit. Hybrid corn has raised the national average to more then 95 bushels an acre. Some states average more than 130 bushels an acre.

A hybridizer produces hybrid seed by first inbreeding. This fixes desirable qualities in the seed. He covers the ears of selected plants to keep airborne pollen from the silk. Later, he takes pollen from the tassels of a plant and dusts it on the silks of the same plant. After inbreeding each strain for several generations, he starts cross-breeding He takes pollen from the tassel of a plant having one desirable strain and dusts it on the silk of a plant with some other strain. The cross-bred product, or hybrid, has the qualities of each parent strain.

Next comes double-crossing. The experimenter dusts pollen from one hybrid onto a hybrid with two other strains. The seed from this cross produces a super corn with four strains bred in. This corn is sold to farmers as seed. Their crop cannot be used as seed next year because hybrid corn is not self-perpetuating. Farmers must buy new seed each year. Great use of hybrid corn threatens the supply of corn pollinated naturally. This loss would restrict improving hybrid strains and prevent developing new ones. To preserve seed of native varieties, the federal government stores seed in corn banks.

Planting and Cultivating

A strong, full crop of corn comes from fertile soil, good seed, thorough cultivation, and clean culture. The soil should be easily worked, well drained, and rich in plant food. The dark loam of the Midwestern United States is particularly well adapted for corn. The farmer chooses the seed to suit conditions on his land. In dry regions he may plant corn in deep furrows. If rainfall is plentiful he puts the seed down in hills or in drills. Once the plant starts to grow, cultivation must never be deep, or the tender, grass like roots will be injured.

Corn draws heavily on the plant food in the soil. Production is higher when corn crops are rotated on a three-year cycle. The first year a legume, such as alfalfa or sweet clover, builds up the soil with nitrogen and humus. The next year corn grows tall on these, its favourite foods. The third year a small grain is planted. Then the cycle is renewed with a legume.

Different Ways of Harvesting

If the farmer wants to store the whole plant in a silo, he cuts the corn while it is still green.

If the corn is to be used for grain, it is not harvested until it is fairly dry. The ears may be picked by hand from the standing corn and husked and thrown into a wagon. On most farms mechanical corn pickers are used.

Some farmers turn cattle in to feed on the corn stalks after the ears are picked. Others cut the stalks, tie them into shocks, and let the ears get dry before husking. Many livestock raisers turn hogs into the ripe fields to feed and fatten on the corn. This method is called hogging down.

Fighting the Enemies of Corn

Corn ear worm (also called tomato fruit worm, or tobacco bud worm, or cotton boll worm), larva of a moth (Heliothis armiger); names vary depending on the various plants it infests; larvae on corn first eat the leaves, then the ears; pupation occurs in the ground; winter ploughing in North kills many pupae.

More than 350 insect pests attack the grain. The most destructive are the corn ear worm, the European corn borer, and the corn root worm Fungus growths, such as smut and various rots, are costly foes. In many cases insecticides are too expensive to be practical.

Therefore the farmer uses the less expensive methods of clean culture and crop rotation. Clean culture means harvesting or destroying every part of the plant. Careful farmers either burn or plough under the stubble. This rids the cornfield of pests that live above the ground. Crop rotation suppresses root pests that live on corn by depriving them of food for one or two years.

Composition of a Corn Kernel

A kernel of corn is wrapped in a tough, fibrous outer hull (bran). Inside is the germ, or embryo, from which the new plant develops. Around the germ is a food supply called endosperm. This is chiefly starch. When the kernel germinates it draws its nourishment from the endosperm until it can put forth roots and leaves and obtain food from the soil and the air.

The moisture content of a kernel varies from 10 to 25 percent, depending upon weather and other conditions under which it was grown. Of the dry portion, about 70 percent is starch (carbohydrates). About 10 percent is gluten (protein), found in a shallow layer just under the hull. The remainder is fat or oil in the germ (4.5 percent), fibre in the hull, and minerals.

A Great Variety of Corn Products

All the parts of a corn kernel can be used to make products. From the whole kernels manufacturers make cornmeal, breakfast foods, and hominy. Some people make hominy at home by removing the hull with lye and cooking the whole grain. When the kernel is crushed it forms hominy grits. Distillers make alcohol and whiskey from whole corn kernels.

Since corn became so dominant a grain in American agriculture, it has naturally found its way to Europe and Asia. There, whether imported or grown locally, it is used mostly for animal feed, as it is in the United States. For humans, corn is less desirable nutritionally than for livestock. The protein value is of low quality, and corn is devoid of niacin one of the B-vitamins that is essential to humans. People who rely heavily on corn in their diets are subject to such niacin-deficiency diseases as pellagra. Corn cannot be used to make leavened bread, although it is much used in Latin America to make dough for such flat breads as tortillas.

The corn products refining, or wet-milling, industry makes a great variety of products from different parts of the corn kernel. Wet milling is so called because the kernels are steeped in tanks of water to soften them, and water is used in the processes that separate germ, gluten, and starch.

First to be separated from the kernel is the germ. Refined and crude corn oil have many uses as human and animal food and in industry. When oil is pressed from the germ a hard cake is left. It is ground into stock feed. One of the proteins in gluten is zein. A synthetic fibre is made from it. It is also used in lacquer, plastics, textile colours, and printing inks.

The final product of the wet-milling separation process is starch. The housewife, food manufacturers, and laundries have many uses for cornstarch. Paper manufacturers use more starch than any other industry to toughen and size (glaze) paper. Textile manufacturers are second. Cotton and synthetic yarns and fabrics are sized with starch.

Glucose (or dextrose, or grape sugar, or corn sugar), simple (monosaccharide) sugar found in fruits and other foods and in the blood of animals; fuels the energy needs for most living organisms.

A huge amount of starch is converted into corn syrups (glucose), sugars, and dextrose by cooking and chemical treatment. These too have countless uses in cooking and in various industrial processes. Even the steep water in which the kernels are soaked is important. Evaporated to a thick, soupy liquid, it is used as a food for the moulds that produce penicillin and other wonder drugs.

Corncobs are ground for a coarse livestock feed. They are used also in a polishing powder, insulation, and a form of sandblasting. Furfural, an oily liquid extracted from corncobs, goes into man-made fibres, drugs, and solvents. Some specially grown cobs are made into pipes for smoking.

Millions of tons of cornstalks are made into a rubber substitute, maizolith. A large quantity is used for making paper and wall board Even the gases from fermenting corn are used to make methyl alcohol.

American Indians had many kinds of corn, and there are now more than 1,000 named varieties. The smallest is the golden thumb popcorn plant, about 18 inches (46 centimetres) high. Some varieties have only eight rows of kernels; others, as many as 48 rows. Colours include white and shades of yellow, red, and blue.

The chief types of corn are pod, soft, sweet, pop, flint, and dent corn. Pod corn has each kernel enclosed in a pod or husk. Soft corn is used for corn flour and for roasting ears.

Sweet corn has the smallest amount of starch; popcorn, the highest. Flint and dent corns lead all other varieties on the grain markets and for livestock feeding. The scientific name of corn is Zea mays.