Giraffe beetle. Also Giraffe weevil.

DEFINITION:1 any of a large order (Coleoptera) of insects, including weevils, with biting mouth parts and hard front wings (elytra ) that cover the membranous hind wings when the hind wings are folded 2 any insect resembling a beetle.

There are more species of beetles than of any other kind of insect. They constitute the largest order of insects Coleoptera which includes almost one third of a million recognized species. About 20 percent of all known species of animals in the world are beetles.

Beetles are found throughout all continents except Antarctica. Although most species are terrestrial, many such as the whirligig, water scavenger, and true water beetles have become adapted to aquatic environments. Some beetles are only about 0.01 inch (0.025 centimetre) long, whereas tropical rhinoceros beetles and Goliath beetles may reach lengths of 4 to 6 inches (10 to 15 centimetres).

Beetles display a remarkable array of colours, forms, and habits. Some are plain black or have brownish patterns that help to camouflage the insects against certain types of wood or soil. Some beetles are brilliant orange, red, or yellow; others are iridescent green or blue or have a metallic sheen. The antennae of some beetles are large and ornate. Some stag beetles have enlarged, hooked mandibles, or lower jaws, that are almost as long as the beetle itself. Male rhinoceros beetles have huge horns projecting over their heads. The shapes of beetles’ bodies vary from round to elongate. Some are flattened; others are domed or cylindrical.

Some beetles are of great significance to humans. Members of the family of beetles known as weevils, or snout beetles, are notorious agricultural pests. They have specialized, elongated heads and down-curved snouts with mouth parts at the end. Some beetles feed on plant materials such as wood, paper, and fabrics. The larvae of some dermestid beetles are destructive pests of clothing and carpets and even of plant and animal specimens in museums.

Many beetles are valuable because they prey on destructive insect pests. Ladybugs, for example, destroy untold numbers of aphids each year and so protect a wide variety of flowers and vegetables. Many other beetles play more subtle but equally important roles in various ecosystems. Dung beetles, or tumble bugs, eat vast quantities of dung in livestock areas. Carrion beetles are scavengers whose larvae feed on dead animals. Many beetles pollinate flowers.

Physical Characteristics

Mandible, from Latin mandere, to chew; term applied to: (1) chewing jaws of insects and other arthropods; (2) the lower jawbone of mammals; (3) the upper or lower part of a bird’s beak.

Like other insects, beetles have three major body segments: the head, with a single pair of antennae and a pair of compound eyes; the thorax, which bears two pairs of wings and three pairs of legs; and the abdomen, where the reproductive organs are housed. Beetles have chewing jaws called mandibles and paired structures known as maxillary and labial palpi (singular, palpus) that are used for feeding or handling food. The bodies of beetles and other insects are covered by a usually hard layer known as the cuticle that supports the internal organs and protects the body. The cuticle is hard because it contains a substance called chitin. Each defined, plate like area of the cuticle is called a sclerite.

A distinctive feature of beetles is their front pair of wings, which are thick, hard, and opaque, without the veins characteristic of most other insect wings. These fore wings, called elytra (singular, elytron), serve as protective wing covers for a second pair of functional wings underneath. The hind wings are membranous and translucent. These are ordinarily used for flying, while the heavy elytra are held out of the way. When the beetle is at rest, the elytra fold over the back and form a straight line down the centre where they meet. Some beetles have shortened wings, and a few species are entirely wingless.

Life Cycle and Behaviour

Like other insects, beetles reproduce sexually by means of internal fertilization. The ovaries of the female and testes of the male are enclosed within the abdomen. In some species, such as the stag beetles, males engage in combat with one another for the right to mate with the females. After mating, the females lay the fertilized eggs in a location suitable for development of the larvae.

Beetles undergo a complete metamorphosis: they develop from egg into active larva into inactive pupa and finally into an adult. The larva, or grub, does not resemble the adult in structure. The pupal stage though soft, pale, and immobile does have the body form of an adult. The life spans of beetles range from a few months in some species to more than four years in others.

Feeding habits. Most beetles feed on living or dead plant materials, but some are scavengers of dead animal matter and some prey on other insects. A few are parasites.

The adults and larvae of a number of beetle species feed on various plant roots, stems, fruits, seeds, and foliage. Some beetles feed only on certain plant species and plant parts, whereas others are less particular in their choice of foods. The adults and larvae of many beetles feed on decaying wood and help break down dead trees and other vegetation in forest habitats.

Some beetles, such as tiger beetles, are voracious predators. Adult tiger beetles search for prey that they can subdue with their powerful mandibles. The larvae are sedentary; they live in small tunnels where they wait to capture passing insects. Water scavenger beetles are predators as larvae but are plant eaters as adults. Some species of beetles have highly selective feeding habits: they may eat only mites, ant larvae, aphids, or zoo plankton

Defences Although most beetles are protected by their heavy armour, some species have developed additional methods of defence Blister beetles secrete an oily, blister-causing substance that deters predators. Beetles may also discourage or avoid predators by making a startling noise (see below, “Light and sound production”), secreting or ejecting an obnoxious fluid, biting, hiding (using their natural colouring as camouflage), or simply fleeing on foot or on wing.

Luminescence, emission of light resulting from causes other than high temperature.

Light and sound production. Many beetles are capable of producing light and sound, primarily for the purposes of attracting a mate or for frightening enemies. The familiar fireflies, or lightning bugs, are beetles that have special light organs on the underside of their abdomens. These beetles usually the males flash their lights rhythmically as a signal that they are ready to mate, and the females return the signal. The kind of signal system used by the two fireflies allows males and females of the same species to recognize and locate one another. Some tropical click beetles have large, luminescent eye spots on the back of the thorax that presumably are also used in courtship.

Many species of beetles make sounds by rubbing together hard parts of their bodies a practice called stridulation. The vibration created by the friction of these parts produces a shrill creaking noise. Beetles may stridulate by rubbing the two elytra together, by rubbing a hind leg against an elytron, or by rubbing the head against the front of the thorax. In some species, even the immature grubs can produce sounds. Although stridulation is often used by adult beetles as a mating signal, its purposes in other instances by juveniles, for example are not fully understood.

A wood-boring beetle known as the death-watch beetle strikes its head against the sides of its burrow as a mating signal. The name death-watch is derived from the superstition that the sound was an omen of death. One explanation is that the ticking sound of a death-watch beetle that had made its burrow in an old piece of furniture was most often heard late at night by someone sitting at a sickbed.

When threatened by a predator, bombardier beetles squirt, with a loud popping sound, an unpleasant-smelling liquid from the rear of their abdomens. The noise and the ejection act together to startle and repel the predator and give the beetle time to make its escape. When click beetles fall on their backs, they right themselves by snapping their bodies in such a way that they are tossed into the air with a loud clicking sound that can startle a predator.

Kinds of Beetles

There are many families of beetles about 135, according to some experts. The beetles discussed below represent a sampling of some of the most commonly known as well as some of the most unusual beetle families in the order Coleoptera.

Tiger beetles and ground beetles are the most common beetles in North America. The fierce, long-legged tiger beetles are fast-running, fast-flying, often brightly coloured beetles that capture and eat other insects. Species of tiger beetles occur throughout the world but are especially abundant in the tropics.

Ground beetle, one of a group of the order Coleoptera, family Carabidae; especially the fiery searcher (Calosoma scrutator), one of the largest beetles; if held carelessly will discharge quantities of “fiery” juice.

Ground beetles are also abundant in most parts of the world. Many species are black and shiny; some are iridescent. Like the tiger beetles, ground beetles have long legs. Some have enlarged, pinching mandibles that are used to capture prey. Many are nocturnal.

True water beetles (also known as diving beetles or predaceous diving beetles) are oval-shaped insects that can swim, dive, and fly. They are found in most freshwater habitats worldwide but are most common in northern temperate regions. The hind pair of legs of the true water beetle are long, flattened, and fringed to provide a greater surface area that helps the insect float. The beetle breathes through spiracles openings on the abdomen just under the tips of the elytra. Before diving, the beetle collects an air bubble beneath its elytra and then breathes from the bubble while it is underwater. It is carnivorous, preying on insects and other aquatic organisms, including fish larger than itself. The larvae of the true water beetles are sometimes called water tigers because of their voracious appetites. True water beetles often fly from one aquatic habitat to another and may be seen around outdoor lights at night.

Whirligig beetles, like the true water beetles, are oval-shaped aquatic predators that can swim, dive, and fly. They are known for their gregarious habits they are usually seen in groups, spinning and whirling around on the surfaces of quiet ponds or lakes. They have distinctive, divided eyes a top pair for seeing above the water’s surface and a bottom pair for seeing below.

Carrion beetles and burying beetles are widely distributed and eat primarily dead animal matter. Many carrion beetles are relatively large and brightly coloured Burying beetles are so named because they dig beneath small dead animals such as rodents, birds, and reptiles until the animal is completely buried beneath the soil. Then the female digs her way down to the carcass and deposits her eggs. Upon hatching, the larvae feed on the body of the dead animal.

Rove beetles have short elytra that do not cover the abdomen. When they are being pursued, rove beetles run with the tip of their abdomens curled over their backs, giving their abdomens the appearance of stingers. One species expels a fluid from the tip of its abdomen that repels attacking ants.

Luminescence, emission of light resulting from causes other than high temperature.

Fireflies are soft-bodied beetles, most of which produce light in special organs located in the undersides of their abdomens. The light is produced by a chemical reaction between oxygen in the air and two chemicals in the firefly’s body. The females of most species have short wings or are wingless. The wingless females and most firefly larvae are often called glow worms Some species in the firefly family do not produce light.

Stag beetles are best known for their enormous, distinctive mandibles. These are most pronounced in the males. Stag beetles are often found in and around rotting logs, on which the larvae feed. Adults are often attracted to outdoor lights.

Scarab beetles include a wide variety of species about 20,000 worldwide. More than 1,300 species occur in North America. Most scarab beetles are stout and robust, but their size varies greatly from one species to another. Some small species are about 0.08 inch (0.2 centimetre) in length, whereas some of the tropical species are the largest beetles in the world up to 6 inches (15 centimetres) in length. Some members of the scarab-beetle family are scavengers: both the larvae and the adults feed on dung and carrion. Others are plant eaters: the larvae eat roots or wood and the adults eat leaves and flowers. Many members of the latter group are agricultural pests. June bugs and May beetles are scarabs.

Click beetles are small to medium-sized beetles with elongated, flattened bodies that have bluntly rounded ends. The largest species reach lengths of about 2 inches (5 centimetres). The larvae of click beetles, called wire worms, cause extensive crop damage in some areas because they feed on underground roots, seeds, and stems.

Metallic wood-boring beetles resemble click beetles in general shape but can be distinguished by their bright metallic colours Some species damage orchards and forests.

Dermestid beetles are mostly small, scavenging beetles. In the household they are particularly harmful to stored foods, leather, furs, and wool products. Although the adults and larvae are scavengers, most of the damage is done by larvae.

Ladybugs, with their roundish, brightly coloured bodies, are the favourite insects of many people. The adults and larvae are often predators of other invertebrates that are agricultural or garden pests, and many fruit growers consider ladybugs to be among the most beneficial of insects.

Darkling beetle, any beetle of the family Tenebrionidae, which includes meal worms, flour beetles, and other species occurring under stones, in dead wood, fungi, and dry vegetable products; most are black or brown.

Darkling beetles include about 15,000 species worldwide. Of the more than 1,400 species in the United States, most are found in the arid South west Most darkling beetles are solid dull black in colour Meal worms are actually the larvae of darkling beetles. Although they are major pests of grain products, meal worms are also commonly raised as food for insect-eating animals such as lizards, frogs, and birds.

Cantharidin, blistering substance obtained from Spanish-fly beetle and other insects of same family.

Blister beetles are elongate, relatively soft-bodied beetles. The adults of most species feed on plants. Blister beetles secrete an irritant called cantharidin. The substance has been used to produce a drug that causes a blistering reaction on the skin most often as a topical skin irritant to remove warts. The substance was first extracted from a bright green blister beetle of southern Europe known as Spanish fly. The drug, also called Spanish fly, was once considered an aphrodisiac, but it can be toxic if taken internally.

Long-horned, wood-boring beetles are often medium-sized to large 0.8 to 2.4 inches (2 to 6.1 centimetres) in length with extremely long antennae. The larvae of these beetles are usually wood-borers that feed on a variety of trees and can cause considerable damage. More than 20,000 species have been described worldwide, and at least 1,200 of these are native to North America. Some are brightly coloured and metallic in appearance.

Leaf beetles are abundant and widely distributed. They are relatively small, and many are brightly coloured and resemble ladybugs. The adults and larvae feed on foliage and also on other plant parts.

Engraver beetle, any of numerous beetles of family Scolytidae; most live under bark of trees and engrave the wood by burrowing.

Bark beetles are considered the most destructive insects of temperate-zone forests. Both the adults and the larvae live beneath the bark of trees. The damage they inflict on the tree depends on the species. Engraver beetles, for example, feed on the inside of the bark and on the surface of the trunk. Other bark beetles bore directly into the trunk and feed on the wood. Ambrosia beetles bore into the tree’s trunk and feed on fungi that live there. Members of the bark-beetle family are dark-coloured. Their antennae are elbowed and have an enlarged, club like end.

Weevils, or snout beetles, constitute an abundant and diverse beetle family with more than 40 subfamilies and 40,000 recognized species. Their most characteristic feature is the beak or snout. It is well-developed, curves downward, and in some species may be twice as long as the body. The snout is used not only for penetration and feeding but also for boring holes in which to lay eggs. The weevils’ antennae are elbowed and club-shaped at the end. Many weevils have no wings; others are excellent fliers. Most are less than 0.25 inch (6 millimetres) in length and are plainly coloured and marked, yet the largest exceed 3 inches (80 millimetres) in length and may be brightly coloured This family includes some extremely destructive pests, such as the grain weevil and the rice weevil.

Taxonomy

Taxonomists divide the Coleoptera into two or more suborders, depending on the classification scheme they prefer. The two suborders common to most schemes are Adephaga and Polyphaga. The suborder Adephaga consists of several families of beetles that are mostly predaceous, including the tiger beetles and ground beetles, the true water beetles, and the whirligig beetles. The suborder Polyphaga contains the majority of beetles.

Tiger beetles and ground beetles belong to the family Carabidae, which contains the largest number of beetle species in North America. (Some taxonomists place tiger beetles in a separate family, Cicindelidae.) Bombardier beetles are also members of the Carabidae family. The true water beetles are in the family Dytiscidae, whirligig beetles are in Gyrinidae, and water scavenger beetles are in Hydrophilidae. Carrion beetles and burying beetles belong to the family Silphidae. Rove beetles are in the family Staphylinidae and have almost as many species in North America as does the family Carabidae. Fireflies and glow worms belong to the family Lampyridae. Stag beetles are in the family Lucanidae. Scarab beetles belong to the family Scarabaeidae, which includes the rhinoceros beetles, Goliath beetles, and dung beetles. Click beetles are in the family Elateridae. Metallic wood-boring beetles are placed in the family Buprestidae. Dermestid beetles belong to the family Dermestidae, and ladybugs are in the family Coccinellidae. Darkling beetles are in the family Tenebrionidae. Blister beetles belong to the family Meloidae. The long-horned wood-boring beetles are classified in the family Cerambycidae, and leaf beetles are placed in the family Chrysomelidae. Bark beetles belong to the family Scolytidae. Weevils belong to the largest family of beetles in the beetle order the family Curculionidae. Bess-bugs belong to the family Passalidae. The death watch beetle is in the family Anobiidae.

Assisted by J. Whitfield Gibbons, Senior Research Ecologist and Professor of Zoology, Savannah River Ecology Laboratory, University of Georgia.

Monarch butterfly

DEFINITION: (or colouring) natural colouration of certain organisms allowing them to blend in with their normal environment and escape detection by enemies.

As animals evolved, most of them developed body colours and markings that improved their chances of surviving. This adaptive mechanism, known as protective colouration, may serve any number of functions. Colouring can help protect an animal by making it hard to see. For an animal that spends much of its life trying to avoid dangerous enemies, this is the most useful function. Thus protective colouration is often found among the most helpless creatures those who have little or no other means of defence A white snow hare, for example, blends into its white surroundings and so becomes less visible to predators.

Conversely, colour can help an organism by making it more conspicuous the bright colours of a poisonous snake may warn off intruders, for example. In general, the purpose of protective colouration is to decrease an organism’s visibility or to alter its appearance to other organisms. Sometimes several forms of protective colouration are superimposed on one animal.

Types of Protective Colouration

There are a variety of protective colouration schemes. Each works in a slightly different manner.

Cryptic colouration helps disguise an animal so that it is less visible to predators or prey. One of the most common types of cryptic colouration is background matching, which may take various forms. Many helpless animals have developed colours and markings that match their surroundings in order to hide from predators. Fish eggs and microscopic zoo plankton, for example, are transparent and nearly invisible as they drift in the upper layers of oceans and freshwater lakes. A fawn’s spotted coat camouflages the animal against the speckled forest floor. Some animals attempt to camouflage themselves physically. The decorator crab, for example, cements bits of algae, seaweed, and other ocean debris onto its shell so that it resembles the ocean floor.

Grasshoppers and other insects that live among green plants are often green, and insects that live in the soil, such as ants, are often earth-coloured. The pepper moth has coloured patches that camouflage it against the tree on which it lives. The Sargasso sea dragon lives amid masses of floating algae. The fish is not only coloured to match the plants, but its fins and scales are even shaped like algae. The oriental leaf butterfly, which lives on leaf-littered forest floors, is so intricately and completely camouflaged that its markings include leaf veins and a stem.

Sometimes it is the predator that is camouflaged. Certain predatory fish, for example, blend in with harmless schooling fish and then prey on members of the school. Some species of groupers are camouflaged against the ocean floor as they lie motionless, waiting for prey to swim by.

Certain animals can change their colour in response to different environments or situations. Certain lizards are well known for their ability to match their colour to their surroundings. Varying hares change colours with the season: through the winter their fur is white, and as the snow disappears, their fur turns brown. Thus they remain camouflaged throughout the year.

Another form of cryptic colouration is called disruptive colouration, a scheme in which spots, stripes, or other colour patterns visually break up an animal’s outline. Such patterns may mask the animal’s true shape or make it difficult for a predator to visually resolve it from a colourful or similarly disruptive background. Predators, such as the cheetah, tiger, and leopard, may use their disruptive colouration to avoid being seen. The spots or stripes on their fur allow them to get close to their prey before being observed, improving their chances of getting food. Many fishes and certain birds exhibit disruptive colouration, as do some snakes. The boa constrictor, a tree dweller that grows to several feet in length, is marked with a complex pattern of spots and stripes so complete that a stripe even extends across its eyes. Some patterns of disruptive colouration operate on the same principle to conceal movement. Snakes that are concentrically banded, for example, are difficult to detect when they move between long blades of grass.

A third form of cryptic colouration is counter shading, designed to mask an organism’s three-dimensional form. Many animals, particularly vertebrates, are counter shaded, or shaded lighter on their lower surfaces and darker on their upper surfaces. This colouration counteracts the effects of overhead light, which accentuates an animal’s three-dimensional form by lightening the animal’s upper body and casting its lower body into shadow.

Counter shading gives the body a more uniform darkness and less depth relief so that the animal is less conspicuous.

Many marine animals are counter shaded so that they will not appear as silhouettes when seen from below. A silhouetted organism would be conspicuous and thus attract predators. When viewed from above, counter shaded marine animals blend into the darkness of the sea bottom; when viewed from below, their light lower bodies match the appearance of the water’s surface.

Alluring colouration Some animals are coloured so that a predator’s attention is drawn to a non-vital part of the animal’s body. The lizard known as the blue-tailed skink has a bright blue tail that the animal can shed at will with no harm to itself. Potential predators are attracted to the tail; if they attack the tail, the skink sheds it and darts away unharmed.

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

Warning colouration is intended not to camouflage an organism but to make it more noticeable. Such colouration is found among animals that have natural defences that they use to deter or fend off predators. These defences can take many forms. An animal may simply cause a disagreeable smell (such as a skunk’s odour), or it may actually cause pain (as from bee’s sting) or even death (as from snake’s venom). Many of these animals are brightly coloured, presumably as a warning to potential aggressors. The monarch butterfly, for example which bears a conspicuous pattern of bright orange and black has such a disagreeable taste that a bird will often regurgitate after eating it. Behavioural biologists believe that predatory animals learn to associate such brightly coloured animals with unpleasant or painful experiences and therefore are likely to pass them up as potential prey in favour of a more drab animal. Common warning colours are red, black, and yellow.

Dewlap, in reptile anatomy, a hanging fold of skin under the neck.

Some organisms can change their colour from drab to bright when threatened. The octopus, for example, turns white when agitated and red when it is suddenly frightened. Certain chameleons, usually camouflaged, display a brightly coloured throat sac, or dewlap, as a warning signal to invaders. Furthermore, when a male chameleon enters another’s territory, the dewlap display of the territory’s “owner” serves as a warning to keep out.

Fin, in zoology, external membrane used for propulsion in water.

Other forms of protective colouration Some animals are coloured in such a way that they draw attention to themselves only when they are in motion. Certain birds have light-coloured feathers that are visible only during flight. When the bird comes to rest, these feathers are tucked under darker feathers, so that the bird is once again inconspicuous. Similarly, many fishes have colourful dorsal fins that are extended while the fish is swimming then folded down when the fish is at rest.

In both cases, the animal can use its colouration to perform a sort of disappearing act. It can draw a predator away from a certain area, perhaps a nest of vulnerable offspring, by catching the predator’s attention and moving to another location. If the predator pursues the decoy, the bird or fish can disappear by coming to rest.

Some organisms imitate the protective colouration of others. This phenomenon is known as mimicry. A harmless animal may display the same warning colouration as a dangerous or inedible one in order to deceive predators into reacting as though the benign animal had the same defences as its model. In other cases, several noxious species will share a similar warning colouration so that potential predators will generalize and avoid all species with such colouring

Evolution of Protective Colouration

The intricate schemes of protective colouration are the results of long-term evolution. Through aeons of adaptive changes, certain organisms have acquired patterns of colouration that have helped them survive and reproduce.

Effective forms of protective colouration have been passed on to following generations. The processes of mutation, natural selection, and reproduction have combined to produce many organisms with colourations that are fine-tuned to their individual environments and their individual protective needs.

Assisted by Elliot Mitchell, science teacher, Latin School of Chicago.

DEFINITION. any of a large family (Aphididae) of small, soft-bodied homopteran insects that suck the juice from plants.

On a stem or on the underside of a leaf sometimes a crowded colony of plant lice, or aphids, may be visible. They are parasites that have sharp sucking beaks and live on the sap of plants. There are many kinds. Most feed exclusively on a particular crop, weed, or tree.

The smallest aphids measure about 1/20 of an inch (0.13 centimetre) in length and the largest about 1/14 of an inch (0.64 centimetre). Most species are green, but some are pink, white, brown, or black. Those that migrate are born with wings. Most generations are made up of wingless females. During the feeding season these females, without mating, produce living young that are all females and that themselves produce several generations of young during the summer. In the fall a generation is born that includes both males and females. After mating, the females of this generation lay eggs that will hatch in the spring to start new colonies.

Aphids secrete from the alimentary canal a sweet watery liquid that is called honeydew. Ants relish this as food. Some species of ants care for whole herds of aphids (so-called “ants’ cows”). The ants build mud shelters for them at the roots of plants and move them often to new pastures as the old ones wither. To induce the flow of honeydew the ants milk the “cows” by stroking them with the antennae. Most aphids, particularly the woolly aphids, spread a white, waxy secretion over themselves for protection.

Many aphids suck plant sap or inject poisonous saliva into plants, causing the plants’ leaves to curl and sometimes drop off. Some aphids produce gall-like swellings on roots and bark. One of the most destructive aphids is the green bug, which infests oats, wheat, and other small grains. Fields of corn are often destroyed by the corn-root aphis, which is dependent on the cornfield ant for survival.

Aphids reproduce so rapidly that if unchecked they can destroy entire fields of crops. Their numbers may be controlled by such natural enemies as ladybird beetles (ladybugs), aphid lions, and lacewings. Farmers frequently control the insects by spraying with pest-control agents. Aphids belong to the order Homoptera and the family Aphididae.

Helen Zille sounding like an African

A fascinating result of evolution is the phenomenon of mimicry, the superficial resemblance of one organism to another that gives the mimicking organism some advantage or protection from predators. Many plants and animals have evolved such resemblances in order to increase their own chances of survival. A walking stick, for example, is an insect that closely resembles the twig of a plant. By virtue of this similarity, or mimicry, it often remains unnoticed by predators. The chameleon is a tree-dwelling lizard that is able to change its body colour to blend in with a variety of backgrounds.

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

Biologists have distinguished between several types of mimicry. In 1861 the English naturalist Henry Walter Bates described a form of mimicry in which the mimic takes advantage of the defences of its model. Such mimicry is called Batesian mimicry. In a well-known instance, the monarch butterfly serves as the model. The monarch is extremely distasteful to many birds; in fact, a bird that eats the monarch will often vomit shortly after its meal. Consequently many otherwise predatory birds will shun the monarch. The viceroy butterfly, which is not distasteful itself, has assumed colouring and markings very similar to the monarch, and thus many birds will avoid it as well. Another example is the harmless snake caterpillar, which can mimic the body and movement of a snake to discourage its natural predators.

Another style of mimicry was described in 1878 by the German zoologist Fritz Muller. In Mullerian mimicry two similar species derive mutual benefits from their resemblance. For example, two wasps, the sand wasp and the yellow jacket, are very similar in appearance, and both can inflict a painful sting. A predator that encounters either the sand wasp or the yellow jacket will learn to associate their colouration with pain and will thenceforth avoid preying on either species.

Anglerfish, marine fishes of the order Lophiiformes with lure-like appendages for baiting prey.

In yet another form of mimicry, called aggressive mimicry, a predator mimics a harmless organism in order to catch its unwitting prey. One aggressive mimic, the angler fish, lies motionless in the water while waving a small fishlike appendage. When a would-be predator approaches to eat the bait, it becomes a quick meal for the angler fish. Another fish, the sabre-toothed blenny, mimics the colour and behaviour of the harmless cleaner wrasse, which feeds on parasites attached to other fish. The blenny uses this resemblance to get close enough to its prey to attack it before it can recognize the deception.

The European cuckoo exhibits a type of parasitic mimicry. It lays its eggs in the nest of a bird whose eggs are similar in appearance. The host bird then raises the cuckoo’s young.

Mimicry is the product of natural selection. Mimicking organisms have developed their particular similarities over time. Each step of the organism’s transition has given it some slight advantage that has increased its chances for survival. For example, a change in colouration that allows a predator to camouflage itself may increase its chances of sneaking up on its prey. Thus it is able to acquire more food and increase its chances of staying healthy, surviving, and reproducing. Evolutionary biologists have used mimicry as a research tool and to help prove Charles Darwin’s theory of evolution. They can trace the evolution of mimicking organisms to learn how long the model and mimic have shared a habitat and to what selective pressures the two organisms have adapted.

Assisted by Elliot Mitchell.

Most people think of wasps only as bugs with bad tempers and sharp stings. Actually, wasps exhibit remarkably sophisticated behaviour and are often helpful, especially to farmers, because they help to check the population of other insects that may be harmful to crops. The many species that feed on nectar travel from flower to flower just as bees do and so are significant as pollinators of various plants. In spite of their reputation, wasps sting humans only when threatened, frightened, or provoked.

Wasps are members of the insect order Hymenoptera, which includes ants, bees, and sawflies. Besides the large and commonly known kinds of wasps, there are a wide variety of small and solitary species. In all, wasps comprise about one-third of the more than 100,000 species in the order.

Wasps characteristically have two pairs of clear, membranous wings, the back pair slightly smaller than the front. Most wasps are strong flyers, but some, such as the female velvet ants, are flightless. As with other insects, the wings and six legs are attached to the middle segment of the body, the thorax. The rear segment, the abdomen, is generally elongated, and the connection between the thorax and abdomen is usually quite narrow. The head has a pair of compound eyes, which form multiple images, and usually three simple eyes, which form single images. The antennae are straight, flexible, and usually composed of 12 or 13 segments. The mouth parts consist of mandibles and maxillae. Mandibles are great, short jaws that are toothed at the tips. Maxillae are smaller mouth parts located behind the mandibles.

Not all species of wasps have stingers. Furthermore, because the stinger is actually a modified ovipositor (a structure used for laying eggs), it is present only in female wasps. The stinger is usually tucked into the tip of the female’s abdomen and is connected to a venom gland. When the wasp stings its insect prey, it injects a poisonous substance that paralyses or kills the victim. Some wasp species that do not sting use their ovipositors to inject their eggs directly into a host insect or plant.

Most wasps are predatory and feed primarily on other insects, including other members of their own order. Their larvae are frequently voracious parasites that eat insects or spiders supplied by the mother wasp. This habit of acquiring animal food to feed their larvae distinguishes these wasps from bees, which nourish their young on plant material.

Wasps may be divided into two groups the social wasps and the solitary wasps though there are species that exhibit characteristics of both.

Social Wasps

Social insects, those living in communities and having differentiated forms or castes, as queens, workers, drones.

These species live in colonies in which responsibilities are divided between three castes: a fertilized female or queen, female workers (usually sterile), and fertile males. In the temperate regions of the world the general reproductive pattern of these wasps begins in the spring when a single queen begins to build a nest in which to lay her eggs. As she builds, other females of the same species join her but remain only as assistants that aid in the construction, food gathering, and care of the larvae. Generally only the original queen is allowed to lay eggs, and she will eat any eggs laid by the accessory females. When the first larvae have become adults, the queen drives away the other females.

This first generation of young is composed exclusively of females whose ovaries are non-functional and who act strictly as workers. They continue with the construction of the nest, care for the next generation of young, forage for food, and feed the queen and each other. It is the second generation of young, emerging in the autumn, that produces the fertile males and females. Shortly thereafter the males are driven from the nest and the young females follow them to be inseminated. Eventually all members of the colony die except for the fertilized queens. They hibernate through the winter, and in spring begin the reproductive cycle again. In the tropics some of the social wasps do not die seasonally, so colonies may persist for several years.

Paper wasp, insect (Polistes fuscatus) of the order Hymenoptera, family Vespidae.

Among the more common social wasps in North America are the hornets and yellow jackets. The female workers of these species, though small, are fiercely protective and highly venomous. Bronze coloured paper wasps are another variety of social wasp. These species and a number of others build their nests from a paper like material made by the wasps themselves. The “paper” consists of plant materials that are chewed and regurgitated by the wasps then stroked into fine strips and glued together.

The hornets are known to build extensive, elaborate nests. They select a location in the branches of shrubbery, in hollow trees, under the frameworks of houses, or in subterranean sites such as mouse nests. First the queen attaches one hexagonal cell to the ceiling by a little stalk, with the opening down. After a week she has created a small plate of five to ten cells. Later, when the numerous workers join in the construction, the nest grows to an impressive size. In subterranean nests the hole may be considerably enlarged to permit expansion. New levels of the comb are added progressively from the top down, with pillars connecting the different tiers. Then the combs are completely covered by a balloon like envelope that may be either elastic or brittle. The single opening, for entrance and exit, is located at the bottom; it also serves as the ventilation hole. The multi-layered envelope both protects the hive and assists in temperature regulation.

Temperature, degree of hotness or coldness measured on a definite scale.

Wasps also are capable of regulating the temperature of the nest themselves. Even on autumn nights when the outside temperature falls to 50 F (10 C), the interior of the nest stays within a half degree of 86 F (30 C). The females accomplish this by moving their flight muscles while keeping their wings motionless, thereby generating heat from their metabolic activity to warm the nest. If, on hot summer days, the outside temperature rises above the 86 F (30 C) optimum for the wasps and their brood, the workers cool the nest by bringing in water and causing it to evaporate by beating their wings.

Solitary Wasps

Most wasps are solitary and harmless. They do not live in colonies, and most do not defend their nests from intruders. Usually these species lay their eggs inside single cells constructed to house the larva and its store of food through the pupation stage (the cocoon phase before the larva emerges as a full adult). Most female wasps lay in a supply of paralysed insects for the larvae to feed upon when they hatch, then seal the entrance to the cell. The insect meals are usually preserved alive to ensure a supply of fresh food for the larvae. Some reports indicate that, if uneaten, these victims may remain paralysed and helpless, but still alive, for as long as four months. After the larva has consumed its ready-made meal, it pupates, and emerges the following summer as a full adult.

Many species of solitary wasps are unusually selective in their choice of the prey they feed their larvae. They may specialize in hunting one particular victim to the exclusion of all others. Surprisingly enough, it seems to make no difference to the larvae they have been known to thrive on an artificial diet. Nevertheless the females continue their single-minded pursuits. One species even hunts only winged female ants, ignoring the many female ants that have already discarded their wings. Naturalists are still at a loss to explain why this wasp then bites off the wings of the captured ants before placing them in her nest.

Representatives of almost all insect orders appear on this select list of prey of the various wasp species. For example, the ensign wasps hunt only cockroaches; the mud daubers only spiders; cicada killers only cicadas; digger wasps only beetle larvae; potter wasps only caterpillars; and the particular bee-killer wasp pursues only the honeybee.

Gall (or gall nut), abnormal growth on leaves, stems, buds, flowers, or roots of plants caused by various parasites, especially insects and mites, and more rarely by nematodes, bacteria, fungi, slime moulds, and algae; found on almost all forms of plant life, but especially common on oak trees, willows, roses, and goldenrod.

The gall wasps, which lay their eggs in the tissues of plants, select not only a particular species of tree or shrub, but also particular parts on the host plant. The developing larvae are a major source of plant galls, or tissue swellings. Those plants commonly affected include the oak trees and rose plants. However, though the galls are unsightly, they ordinarily do little harm to the plants because they are relatively small and localized.

Some species of solitary wasps prefer not to expend their energy on nest building, hunting, and child care. They are noted for smuggling their eggs into the cells of other wasps, a practice called brood parasitism. The cuckoo wasps, small, flying wasps with bright metallic green or blue colouring, are among the most beautiful of the order Hymenoptera, and they are all parasites. The female usually lays her eggs inside the nests of bees, thread-waisted wasps, or yellow jackets. If she is caught in the act and attacked, she rolls herself into a ball to protect herself from the nest owner’s stings. Finally she is thrown from the nest and left for dead; she emerges unscathed. If the cuckoo wasp is successful in laying her egg, the host does not notice the deception. When the cuckoo wasp larva hatches, it eats the host’s larvae along with any food stored for them. It then spends the winter as a pupa and emerges in the spring as an adult.

Another group of parasitic wasps, the velvet ants, are common in most parts of the world, particularly in the Southern and South western United States. Despite their name, the velvet ants are not true ants. They were mistakenly named after the females, which are wingless. Many members of the species are brightly coloured often scarlet or yellow. The largest members of the velvet ants, the so-called cow killers, are bright orange or red. They reach lengths of up to 1 inch (2.5 centimetres) and have stingers that are almost half again the length of the body. Like the cuckoo wasps, the velvet ant is a parasite that lays its eggs in the nests of other insects. Although the velvet ants generally select other wasps or bumblebees to act as hosts, a variety of other insects have been identified as their hosts, including mud daubers in North America, bumblebees in Europe, and tsetse flies in Africa.

Wasps exhibit a wide range of behaviours, not all easily categorized. Some non parasitic solitary wasps check on their larvae regularly, bringing them fresh stores of food whenever necessary and sealing the nest only when the larvae have pupated. Others lay their eggs on temporarily paralysed hosts, then leave the young to fend for themselves. In the latter case the unfortunate host, having regained the use of its limbs, continues about its business undaunted until the larvae hatch and begin to consume its body. Another species of wasp exhibits a highly unusual form of social parasitism. The parasitic queen invades the nest of a colony of social wasps, demotes the queen to worker, and assumes her throne. In this case the former queen lays no more eggs, the host wasps care for the offspring of the conqueror, and the host species dies out without descendants.

Wasps are found throughout the world on every continent except Antarctica and on all major islands. Several thousand species of wasps occur in North America, but wasps are most numerous and their species most diverse in tropical areas. Some of the parasitic wasps are the smallest insects in the world, reaching maximum lengths of less than 0.008 inch (0.02 centimetre). The largest wasps reach lengths of more than 2 1/4 inches (6 centimetres).

The stinging wasps belong to the suborder Apocrita of the order Hymenoptera, the non stinging wasps to the suborder Symphyta. The majority of the social wasps belong to the family Vespidae, and can be distinguished from most other wasps by the way they fold their wings like a closed fan along their back when at rest. Many members of the Vespidae are black with bright yellow or white cross bands or other markings. Hornets and yellow jackets belong to the subfamily Vespinae, whose members are widespread throughout North America, Northern Africa, Europe, and Asia. The paper wasps belong to the subfamily Polistinae, which contains more than 150 species throughout the world.

The families of solitary wasps are numerous and varied. The ensign wasps belong to the family Evaniidae, the mud daubers and cicada killers to the family Sphecidae, digger wasps to the family Scoliidae, and potter wasps to the subfamily Eumeninae of the family Vespidae. Other wasp families include the Cynipidae (gall wasps), Chrysididae (cuckoo wasps), and Mutillidae (velvet ants).

Assisted by J. Whitfield Gibbons, Senior Research Ecologist and Professor of Zoology, Savannah River Ecology Laboratory, University of Georgia.

He admitted a small beam of sunlight into a darkened room and passed it through a prism. The beam produced a band of colours just like the rainbow, ranging from red through yellow, green, and blue to violet. He then passed each of these colours through other prisms and found that they did not change. But when he passed the whole band of coloured lights through a prism in reverse position, the coloured band became white sunlight again.

From this he reasoned that white light is really a mixture of coloured lights, and that each colour is bent by a different amount when it passes through the prism. This difference in bending enables each colour to stand out separately and be visible. The band of coloured lights thus formed is called a spectrum. The rainbow is actually a spectrum, formed by sunlight passing through raindrops.

Separating light into its colours is called dispersion. It is accomplished by refraction (bending) of light in the prism. Each of the colours has its own wavelength. The wavelength determines how much each colour will bend. Red bends the least, violet the most. If the light beam strikes the prism at a certain angle, the amount of bending for each colour is always the same. Each colour then falls in exactly the same place on a screen, so its position is enough to identify it.

Scientists use the dispersive action of the prism in the spectroscope. The spectroscope reveals that the spectral pattern of light is different for various classes of light sources. Light from the sun, from certain lamp filaments, and from molten metals each produces a spectrum which has all colours in an unbroken array. Such a pattern is called a continuous spectrum. Incandescent gases give off only certain colours, in fine lines. Their spectra are called bright-line spectra. Both bright-line and continuous spectra are emission spectra, produced by emitted light.

Fraunhofer, Joseph von (1787-1826), German optician and physicist; worked to improve optical instruments; invented a heliometer and a micrometer.

In the early 1800s Joseph von Fraunhofer observed that the continuous spectrum was crossed by many dark lines. He charted more than 700 of them, but he was unable to explain their meaning. Because of his discovery, however, they are called Fraunhofer lines.

Kirchhoff, Gustav Robert (1824-87), German physicist, born in Konigsberg, East Prussia (now Kaliningrad, Russia); developed spectrum analysis and discovered caesium and rubidium (with Bunsen); explained the Fraunhofer lines; professor of physics at Heidelberg 1854-74, at Berlin 1874-87.

The meaning of the Fraunhofer lines was discovered about 50 years later by Gustav Kirchhoff and Robert Bunsen. With a spectroscope they studied the spectra of certain substances which were vaporized in the non luminous Bunsen burner flame. Each vapour showed a characteristic bright-line spectrum. But when emitted light was passed through a cooler vapour of the same substance, the bright lines were replaced by dark ones in the same position.

This replacement of bright by dark lines meant that the second vapour had absorbed the characteristic light of the first. Later experiments showed that the cooler vapour absorbs those light waves which it would normally emit at a higher temperature. In 1859 Kirchhoff published his findings in his laws of radiation and absorption. The spectral pattern thus formed is called a dark-line, or absorption, spectrum.

Kirchhoff and Bunsen also noticed that characteristic arrays of lines are given off by the different chemical elements. For example, incandescent sodium always gives certain yellow lines near the middle of the spectrum, and no other element gives these lines. Thus when these lines appear, sodium must be present in the incandescent substance. If the lines are bright the light has come directly from the incandescent sodium. If they are dark the light has passed, somewhere along its path, through an absorbing vapour containing some gaseous sodium. Only minute quantities of an element are needed to make its lines appear. This makes it possible to identify the elements in unknown substances.

These discoveries not only explained the Fraunhofer lines in the spectrum of sunlight but made it possible to determine what chemical elements the sun contains. The absorption necessary to produce the dark lines was considered as taking place in the outer layers of incandescent gas surrounding the sun. For “analysis” of the sun, the dark lines could be compared with the bright-line spectra of different elements produced in the laboratory. Whenever they corresponded, scientists could be sure that the element existed in the sun. Stars likewise could be “analysed” as to chemical contents by this method.

Janssen, Pierre-Jules-Cesar (1824-1907), French astronomer, born in Paris; discoverer of helium in sun; founded and directed observatory on Mont Blanc 1893.

Lockyer, Joseph Norman (1836-1920), British astronomer and physicist, born in Rugby, England; pioneer in application of spectroscope to sun and stars; explained sunspots; between 1870 and 1905 conducted eight British expeditions for observing total solar eclipses (‘The Sun’s Place in Nature’; ‘Recent and Coming Eclipses’; ‘The Chemistry of the Sun’; ‘Inorganic Evolution’).

Ramsay, William (1852-1916), British chemist, born in Glasgow, Scotland; professor Bristol University 1880-87, University of London 1887-1913; discoverer of helium, neon, krypton, xenon; co-discoverer of argon; research in radioactivity led to new theory of transmutation of elements; knighted 1902; received 1904 Nobel prize.

Cleveite, mineral, oxide of uranium and lead; named for Per Theodor Cleve, a Swedish chemist; produces helium when heated with acid.

Scientists have obtained spectra corresponding to the different elements and have measured and charted every line. When they wish to learn the composition of a star, they photograph its spectrum and then check the lines against these charts for the elements. A notable triumph of the method was the discovery of helium. In 1868 P.J.C. Janssen (1824-1907), a French astronomer, and the English astronomer, Sir Norman Lockyer (1836-1920), independently discovered lines in the solar spectrum which could not be identified with the charted lines of any known element. Lockyer interpreted this to mean that an element unknown to us existed in the sun. He named it helium, after helios, Greek for “sun.” Then in 1895 Sir William Ramsay (1852-1916) found that the Norwegian mineral cleveite, when heated, gave off minute quantities of a light gas which he identified as helium by means of its spectrum.

Measuring Light Waves

Millimicron (mm), unit of wave length equal to one millionth of a millimetre or one thousandth of a micron; sometimes used in the measurement of light waves.

Angstrom unit (A, or A.U.), ten-millionth of a millimetre, used to describe length of light waves; named to honour Anders Jonas Angstrom.

Nanometre (nm), measuring unit in spectroscopy, equalling one billionth of a meter.

The units once commonly used to measure wavelengths were the millimicron, denoted by the symbol mm and equalling one millionth of a millimetre; and the Angstrom unit (A or A.U.), one ten millionth of a millimetre Wavelengths are still measured in various units, but the unit most commonly used in spectroscopic work today is the nanometre (nm), which is equal in length to the unit it replaced, the millimicron. This is one of the special units which science has accepted as a means of avoiding the excessively long decimal fractions which would be needed to express wavelengths as short as those of light, if measured in inches or centimetres For example, violet light has a wavelength of 410 nanometres. The following table gives the wavelengths which fall approximately in the centre of each of the coloured regions in visible light:

Violet 410 nanometres

Blue 470

Green 520

Yellow 570

Orange 620

Red 710

Since the colour of light is determined by its wavelength, this means that the shorter the wavelength the more the light is bent by passage through a given prism. Thus the wavelength (and the frequency) of the vibration causing the wave is judged from the amount of bending given by the prism. This is determined by the position of the spectral line on the screen or photographic plate.

Prism and Diffraction-Grating Spectroscopes

Modern spectroscopes used in very technical fields vary considerably in function and design and are often quite specialized for the specific substances they analyse However, the fundamental teaching instruments generally used in today’s classrooms are the relatively simple prism spectroscopes. These consist of a collimator (tube for admitting light), a glass prism, and a telescope. The collimator has a slit at one end to admit light and a lens on the other to concentrate it. The lens directs the light on the prism, which disperses the ray into its component colours Sometimes a train of prisms is used to increase the dispersion.

After the colours leave the prism they are focused on the object glass of the telescope. Each wavelength appears as a separate image of the collimator slit. When the telescope is replaced by a camera to photograph the lines, the device is called a spectrograph.

Rowland, Henry Augustus (1848-1901), U.S. physicist, born in Honesdale, Pa.; professor Johns Hopkins University 25 years; determined ohm and the mechanical equivalent of heat; discovered magnetic effect of electric convection.

A more powerful type of spectroscope uses a diffraction grating, invented by Fraunhofer in 1821. He made it by twisting a fine wire about two tiny screws. With it he measured the wavelengths of light with surprising precision. The modern precision grating consists of a plate of speculum metal or glass upon which fine lines, equidistant and parallel, have been ruled. Among the finest of these are the gratings made by H. A. Rowland. He invented a machine to rule the entire grating automatically, etching from 14,000 to 20,000 lines per 1 inch (2.5 centimetres). By means of such a grating, made on a concave surface, Rowland secured a spectrum band of sunlight more than 20 feet (6 meters) long. The grating uses a special application of the interference phenomenon of light.

Diffraction-grating spectroscopes can measure the wavelength of light with a precision of .000,000,000,001 centimetre (10^-12 centimetre). It is used as the dispersing medium in analysing visible light and ultraviolet rays. A photographic plate is usually used as the detecting device in the analysis.

Motion, Temperature, Magnetism

Doppler effect, law in physics discovered by Christian Doppler (1803-53); applied to sound, light, and radar from moving sources.

The spectroscope can also tell the astronomer whether a star is moving toward or away from the Earth by means of a phenomenon known as the Doppler effect. Everyone has noticed how the whistle of an approaching locomotive rises to a shrill note as it approaches then drops to a lower and lower tone as the train rushes away. The reason for this is that when the train approaches, its whistle is nearer to us each time a sound wave is emitted. The successive waves reach us a little more quickly and therefore have a higher pitch. When the train is receding, the waves are dragged out, and thus the pitch of the whistle is lowered.

Similarly, when a star moves toward the Earth, each light wave is shortened a little. Consequently, the lines shift their position toward the violet end of the star’s spectrum. When the star is moving away from the Earth, the wavelengths are lengthened somewhat, and the lines in the spectrum shift a little toward the red end. The amount of shift reveals the speed of the star’s motion; but since light in a vacuum travels at the tremendous speed of 186,282 miles per second (299,743 kilometres per second), the star must be travelling at a very great speed to create a noticeable effect.

Temperature, degree of hotness or coldness measured on a definite scale.

Temperature and pressure have certain effects on spectra. These effects can be detected and used to determine the approximate temperature of stars and the pressure of gases on distant bodies.

Zeeman, Pieter (1865-1943), Dutch physicist; professor physics and director Physical Institute, University of Amsterdam, 1900-35; discovered the Zeeman effect of magnetism on light; Nobel prize 1902.

Another marvellous revelation of the spectroscope is the connection between magnetism and light. In 1896 the Dutch physicist Pieter Zeeman (1865-1943) discovered that when light passed through the field of a strong electromagnet, the lines in the resulting spectrum were split into two or more lines. This influence of magnetism on light, which was named the Zeeman effect after its discoverer, has proved to be valuable in the detection and measurement of magnetism in the sun.

The Electromagnetic Spectrum

The coloured lights in the rainbow make up but a small portion of that huge spectrum of energy called electromagnetic radiation. The other groups include radio waves, microwaves, infra red light (heat), ultraviolet rays, X rays, and gamma rays. Despite the different effects they produce, each of these forms of energy travels through space as an electromagnetic disturbance. They are sometimes called forms of radiant energy.

Study of the lines in various spectra has helped build the modern theory of matter. Soon after Bunsen and Kirchhoff developed the use of spectral lines as a means of chemical analysis, scientists thought that the various lines were given off by atoms vibrating at different rates under the stimulus of heat. They believed that the faster vibrations resulted in the shorter waves that caused lines to appear toward the violet end of the spectrum.

Rydberg, Johannes Robert (1854-1919), Swedish physicist; worked on the spectrum.

In 1885 Johann Jakob Balmer (1825-98) discovered through experimentation that the various rates of vibration in a mass of glowing hydrogen bore a simple mathematical relation to each other. This indicated that some one type of “mechanism” was at work at varying rates within the hydrogen atom, giving off the different wavelengths. Balmer could not guess what this “mechanism” might be, however. Then Johannes Robert Rydberg (1854-1919) introduced further information on this subject and developed a formula named for him that described many more observed relations; but he also did not know what it was within the atom that vibrated. Finally, the answer came in 1913 from Niels Bohr (1885-1962), the renowned Danish physicist.

Bohr’s theory, built largely upon knowledge from the study of radioactivity, held that the hydrogen atom consisted of an electron revolving like a planet around a central nucleus, or “sun.” Bohr believed further that as an atom absorbed energy by being heated, for example this orbit would enlarge by definite amounts, each enlargement representing the absorption of one quantum, or “packet,” of energy. When energy was emitted, as in the form of light, the electron would fall by steps into inner orbits, and the frequency of the light would depend upon how many orbits were traversed. If the electron fell inward by one orbit, the “energy splash” resulting from this would travel outward as light of a certain frequency. If it fell inward by two orbits, light of a different frequency would go forth. The collection of lines given by hydrogen in a spectroscope sums up these actions taking place in all the hydrogen atoms present. Furthermore, by using the Planck constant (the fundamental measurement of a quantum) and electrical factors in a formula of the Rydberg type, Bohr was able to reduce his whole explanation to terms of electrical force. Thus the spectrum of hydrogen was explained as the product of electrical forces within the atom, and the spectroscope became useful for studying the structure of matter.

Another significant discovery was that X rays could be made to give spectra just as visible light did. This was done by causing a beam of X rays to fall upon a crystal. The short rays of the X rays were diffracted in a pattern that revealed the arrangement of atoms in the crystal.

In 1913 and 1914 the English physicist H.G.J. Moseley (1887-1915) announced the discovery of far-reaching relations among X rays produced from the surfaces of different metals by the impact of electrons. He found that each metal gives certain groups of X-ray lines, corresponding to certain frequencies. As he passed from a lighter to a heavier metal, each successive element showed lines of higher frequencies. Moseley reasoned that this was not due to increasing atomic weight, since several substances of different atomic weights showed the same spectra. It must have been due to a regular increase in the number of orbiting electrons, corresponding to the atomic number, of the atoms of the metals. Moseley’s work provided the basis for the modern periodic classification of elements.

Modern Applications

Spectroscopes are used in almost every technical field, especially for identifying constituents and processes in any source that emits light. In some industries many similar samples must be analysed quickly and simultaneously for their light-absorbing characteristics. A physician may have several hundred samples of blood serum to analyse in a short period of time. Fortunately, fully automated analytical spectroscopes are available. New techniques of analysing samples based on how they absorb radiation to differing extents have given scientists new ways to determine a substance’s properties. Infra-red spectroscopy, ultraviolet spectroscopy, and nuclear magnetic resonance spectroscopy are the most commonly used of such techniques.

In the 20th century, scientists discovered that all atomic particles behave as if they had wavelengths much like those of light waves. Spectroscopes were used to study these particles. The study of the various elementary particles themselves is divided into baryon and meson spectroscopy, and elementary-particle spectrometers are used for such studies. One of the accomplishments of neutron spectroscopy, another field, was the plotting of the structure of large complex molecules like those of DNA and RNA, the basic materials of heredity. Furthermore, spectroscopes are used to measure temperatures in controlled thermonuclear fusion.

AD 395: Division of the Roman Empire. Emperor Theodosius I died in 395. He had appointed two successors: his older son, 17-year-old Arcadius, was given rule over the east; and his younger son, 10-year-old Honorius, was given authority in the west. Honorius ruled from Milan, however, not from Rome.

This division of the Roman Empire between Arcadius and Honorius was meant to be temporary, but it became permanent. The Eastern Empire, more commonly called the Byzantine Empire, took on a life of its own, while the empire in the West disintegrated under the impact of barbarian invasions until it collapsed in the 5th century. The Eastern Empire endured until 1453, when it was conquered by Ottoman Turks. It contributed much to civilization through the arts, particularly its fabulous mosaics. Its most famous ruler was Justinian I, creator of the Code of Justinian, a collection of past imperial decrees that influenced legal theory for centuries to come.

The two parts of the old empire differed religiously, too. In the West the leadership of Christianity was gradually assumed by the bishop at Rome, the pope. In the East, the patriarch of Constantinople was the head of Christianity. This separation pushed Christianity in two different directions, until a split occurred in 1054, when the religion was divided between Roman Catholicism in the West and Eastern Orthodoxy in the East.

AD 726: Iconoclastic Controversy One of the chief divisions in early Christianity arose over the issue of icons. An icon is a religious image, usually a depiction of a saint. Those who opposed the use in churches of images such as statues charged that it was a pagan custom. They thought that people attached too much importance to the icons and came to believe that the icons had their own powers, rather than merely representing the power of God.

In 726 the Byzantine emperor Leo III banned the use of images, launching the Iconoclastic, or “image-breaking,” Controversy. Five years later the Roman pope Gregory III threatened to excommunicate all iconoclasts. The argument within the churches lasted until 843 and fuelled the already bitter differences between the Western church, based in Rome, and the Eastern church, based in Constantinople. The two churches Roman Catholic and Eastern Orthodox finally broke with each other in 1054.

1054: East-West schism in Christianity. The final split separating the Eastern Orthodox and Roman Catholic churches came in 1054, after centuries of disagreement. In this year Pope Leo IX and Patriarch Michael Cerularius excommunicated each other.

One source of contention concerned the use of images, or icons, in churches. Another dispute centred on the authority of the Pope, who is the bishop of Rome, over the churches. As hopes of reconciliation faded, the patriarchs of the Eastern churches gradually renounced allegiance to Rome and paid homage to the Patriarch of Constantinople as the “first among equals.”

The schism has never been healed, but in the 20th century the two large branches do have relations with one another. Most Orthodox churches have joined with Protestant denominations to form the World Council of Churches, established in 1948, but the Roman Catholic Church is not a member.

Organization

Patriarch (from Greek, meaning father and rule), father and ruler of a family or tribe; in biblical history applied particularly to Abraham, Isaac, and Jacob; in Roman Catholicism term used to signify a bishop of the highest rank, and in Greek church a high dignitary, such as the patriarch of Constantinople.

Eastern Orthodoxy is a fellowship of autonomous, or independent self-governing, churches, each of which is under the rule of a bishop. The patriarch of Constantinople (now Istanbul) is considered the first among equals, but he has no authority comparable to that of the Roman pope.

Union of Soviet Socialist Republics (commonly called Soviet Union, formerly Russia), from 1917 to 1991 country of e. Europe and of w.-central and n. Asia; cap. Moscow. Circa 1995.

Turkey (officially Republic of Turkey), country of Asia and Europe; 301,380 sq mi (780,570 sq km); cap. Ankara, lying in Asia; pop. 58,584,000. Circa 1995.

The number of independent churches has varied throughout history. Today there are the Church of Constantinople, the Church of Alexandria (Egypt), the Church of Antioch (head quartered at Damascus, Syria), the Church of Jerusalem, the Russian Orthodox church, the Church of Georgia, the Church of Serbia, the Church of Romania, the Church of Bulgaria, the Church of Cyprus, the Church of Greece, the Church of Albania, the Polish Orthodox church, the Ukrainian Orthodox Church, and the churches of the Czech Republic and Slovakia. There are also smaller autonomous churches in Finland, Crete, and Japan and many in the United States. Many of the churches existed in hostile surroundings. The Russian Orthodox church suffered severe persecution in the past. It was forced to cooperate with the authorities of the Soviet Union in order to function until the restructuring of Communism allowed open worship after 1990. The church in Albania has been outlawed altogether. The members of the churches in Turkey, Egypt, and the Middle East live as minorities amid large Muslim majorities. Eastern Orthodoxy in the United States is represented by almost every national Orthodox body.

The Orthodox understanding of the church is based on the principle that each local community of Christians, gathered around its bishop and celebrating the Lord’s Supper, or Eucharist, is a local realization of the whole church on Earth. This concept of wholeness is called catholicity. This may seem an abstract concept, but what it means essentially is that everything necessary to be a church is found in the local congregation. The idea of catholicity may be compared to a loaf of bread. Each single slice is not the whole loaf, but each slice has all the ingredients necessary to be bread. Hence, wherever a bishop and congregation are gathered together, there is the church.

This continuity of the church is demonstrated by the fact that the consecration of a bishop requires the presence of several other bishops. This testifies to the continuity of the whole church in the present and to its unbroken heritage from the time of the Apostles.

Besides bishops, there are two other orders of clergy priests and deacons. These may be married men, though bishops are always chosen from among unmarried or widowed clergy.

Eastern Orthodoxy also has a strong tradition of monasticism, dating back to the 3rd and 4th centuries. It has been primarily a contemplative movement, seeking to experience God through a life of prayer. There has not been the development of religious orders with missionary or educational goals as in Western Christianity.

Belief and Worship

Eastern Orthodoxy considers itself the bearer of an unbroken living tradition of Christian faith and worship inherited from the earliest believers. Its beliefs are based on consistency with the Bible and tradition as expressed in the ancient councils the seven ecumenical church councils that took place between 325 and 787. The churches also accept the decrees of some later councils as reflecting the same faith.

Lord’s Supper (or Holy Eucharist, or Communion), Christian rite in which bread and wine (or grape juice) are taken in commemoration of Christ’s death; sacrament was instituted by Christ at his supper (Lord’s Supper, or Last Supper) with his disciples the night before his death (Bible, Matt. xxvi, 26-29; Mark xiv, 22-25; Luke xxii, 14-20).

The churches accept seven sacraments, or holy acts: baptism, chrismation (similar to confirmation), the Lord’s Supper, ordination, penance, anointing of the sick (called extreme unction in the West), and marriage. This number of sacraments was never defined in the early church. It was only in response to the Protestant Reformers of the 16th century, who accepted only two sacraments, that the number seven was determined.

The sacrament of chrismation is peculiar to the Eastern churches. In it newly baptised infants are anointed with oil and immediately admitted to the Lord’s Supper. In Western churches children must wait until they are older before receiving their first communion. In admitting infants the Orthodox churches maintain that baptism is the beginning of a new life that must be sustained by the Eucharist. When given communion, the bread is dipped in the wine a procedure called intinction and administered to, or placed on the tongue of, the recipient.

Liturgy (from Latin liturgia, meaning “a public service”), term applied to any or all of the services used in public worship; especially in Roman Catholic, Eastern Orthodox, and Episcopal churches.

Liturgies. Forms of worship are called liturgies. The two chief Eucharistic liturgies in the Orthodox churches are those of St. John Chrysostom and of St. Basil the Great. Both acquired their present form in the 9th century. There is also a liturgy of St. James, often used in Jerusalem. All of the liturgies are elaborate, festive occasions.

The liturgies are divided into three segments. The first is a rite of preparation, during which the priest puts on a plate particles of bread symbolizing the gathering of the saints, both living and dead, around the living Christ. This is followed by the liturgy of the catechumens, or learners. This segment includes the reading of the lessons and the sermon. Finally comes the liturgy of the faithful, or baptised Christians, which includes the recitation of the creed and the administering of communion.

The Orthodox churches follow the traditional church calendar, the church year beginning with Advent, four Sundays before Christmas. The greatest festival is Easter. The date of Easter normally varies from its celebration in the West because the Eastern churches still use the Julian calendar to compute the date.

The Orthodox churches have a rich tradition of musical composition for hymns and liturgies. Since the Orthodox tradition bans the use of musical instruments or accompaniment (with the exception of some American congregations), all singing is done without musical accompaniment.

Santa Sophia (in Greek, Hagia Sophia, meaning “holy wisdom”), building in Istanbul, Turkey, erected as Christian church in 6th century by Justinian I; became Muslim mosque in 1453; in 1935 was made a museum of Byzantine antiquities.

Architecture. Some of the most beautiful and highly decorated church buildings in the world have been built by Christians of the Orthodox tradition. The first major house of worship, and still one of the great buildings of the world, was built during the reign of Emperor Justinian I in the 6th century at Constantinople. It is the Hagia Sophia, or Holy Wisdom. It consists of a huge round dome set atop a classical basilica-style building. Most Orthodox churches today have one or more domes. The Hagia Sophia was turned into a mosque by the Ottoman Turks, and later it became a museum.

Iconostasis, screen, or wall, in interiors of Eastern Orthodox churches.

The interior of an Orthodox church is somewhat different from other churches. In most Western churches the altar is readily visible from the entryway. But in Orthodox churches there is a screen, or wall, called an iconostasis, with one or more doors in it, largely concealing the altar area from the worshippers It is called an iconostasis because it is richly decorated with icons in the form of pictures of Christ and the saints. Orthodox churches have no statues or other three-dimensional images. The purpose of the iconostasis is to suggest a contrast between the visible manifestation of God in Christ as a man and his more perfect and invisible presence in the communion.

It is largely because of its emphasis on the gathered community in worship that the Orthodox churches have survived in often hostile surroundings. For this reason it is impossible to overestimate the significance of the liturgy in the life of the Eastern churches.