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BEES (Part 1 of 3)   Leave a comment

 

DEFINITION: any of a large super family (Apoidea) of broad-bodied, four-winged, hairy hymenopteran insects that gather pollen and nectar, have biting as well as sucking mouth parts, and often live in organized colonies; esp., the honeybee.

People have known ever since ancient times that the insects called bees make delicious honey from the nectar of flowers. There are more than 20,000 species of bees, and they are found all over the world except in Antarctica. Most people throughout the world recognize honeybees, and people in temperate regions know bumblebees as well (in some places they are called humble-bees). In Central America and South America many persons are familiar with tropical sting-less bees.

Physical Characteristics

Bees are flying insects that are related to wasps, hornets, and ants. Most bees have short, thick bodies covered with hair and, like all insects, six legs and three body parts: head, thorax, and abdomen. The thorax in turn has three segments, each with a pair of legs. A tiny waist connects the thorax and abdomen.

Ordinarily, most bees fly about 12 1/2 miles (20 kilometres) per hour, but they can fly much faster. They have two pairs of wings. One pair is attached to each of the last two segments of the thorax, but front and back wings are joined so that they may look like only one. The rapid movements of the wings make a humming sound in flight.

With three single eyes on top of their heads and two huge, helmet-like compound eyes, bees can see colour, pattern, and movement. The many facets of their compound eyes give them a total image in a mosaic of dots. Bees see all colours humans do except red, and they see ultraviolet, which humans cannot. Ultraviolet is often reflected by red flowers. Bees can also detect the polarization of light, which humans cannot. For example, in a blue sky polarized light forms a distinctive pattern around the sun, and even when the sun is behind the clouds bees can perceive that pattern and orient themselves to it.

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.

Proboscis, snout, trunk, or other tubular organ projecting from the head of an animal.

On the lower part of their heads bees have biting jaws (mandibles) and a mouth-tongue proboscis, of several parts, which they use for sucking and lapping. Bees can distinguish very slight differences in sweet and bitter tastes, and they can also identify sour and salty tastes. Their front legs and feelers (antennae), as well as their proboscises are used for tasting. The antennae are primarily for sensing fragrances: bees find the perfumes of flowers even more enticing than their colours and shapes. Bees have no ears, but they can sense the vibrations of the surfaces upon which they alight.

The largest bees, which include some of the leaf cutter and carpenter varieties, may be up to about 1 1/2 inches (4 centimetres) long. Bumblebees are larger than most about 1 inch (2.5 centimetres) long. Honeybees range from about 1/2 inch to 1 inch (1.3 to 2.5 centimetres) long, depending upon the species. Some of the small leaf cutter bees are only 2/5 inch (1 centimetre) long, and sweat bees are 3/10 inch (0.7 centimetre) long. The tiniest species, the mosquito bees, may be only 3/50 inch (0.2 centimetre) long.

Most bees have black bodies, many with yellow or brown markings. Others have yellow, red, brown, and metallic green or blue bodies, some with brilliant metallic red or purple markings. Honeybees are dark brown with dark yellow stripes. Bumblebees are usually black with wide yellow or orange bands.

Food from Flowers

Honeycomb, a waxy many-celled structure made by bees for holding honey.

Depending upon its size and the length of its proboscis, a bee can enter many kinds of blossoms to sip nectar, the sweet liquid secreted by the flower’s glands. The bumblebee has a long proboscis and so is better equipped than many others for taking nectar from red clover, the flowers of which are made up of clusters of tubular blossoms. The nectar is carried in a special part of the bee’s stomach. During the digestive process enzymes are added, and the nectar becomes honey. Later it is regurgitated into the cells of the comb within the hive. When full, the cells are left until the honey has dried and thickened to the right consistency. Then the bees cap the cells with wax to preserve the honey and prevent further drying.

Pollen gathered from flowers clings to special branched or feathered hairs on the bee’s body. After pollen has accumulated, the bee brushes it off and moulds it into tiny balls mixed with honey from its mouth. This is beebread, the food of the young bees. The bee pushes these pellets into a particular formation of hairs or bristles for carrying them back to the nest. Honeybees have a pollen basket of stiff hairs on their hind legs. Leaf cutting bees have a dense brush on the underside of the abdomen.

Pollination

Fascinated by both colour and shape, bees show a strong preference for flowers with elaborate embellishments and respond eagerly to patterns of colour, particularly of yellow, blue, and ultraviolet. A more deeply shaded pattern is present near the centre of some blossoms. This clearly marked area acts as a carpet of colour to guide the bee to the nectar.

Snapdragon, herbaceous plants composing the genus Antirrhinum of the figwort family with showy white, yellow, pink, or red flowers; lower lip of large tubular corolla snaps shut if opened; many beautiful garden varieties have been derived from Antirrhinum majus.

The liplike petals of many flowers provide a place where a bee can land before entering. When a bumblebee alights on the lip of a snapdragon, the bumblebee’s weight, which is greater than that of most bees, opens the flower’s mouth, letting the bee enter the inner chamber to sip the nectar.

As bees go from one blossom to another, much of the pollen that clings to their bodies is transferred to the flowers of other plants of the same species, pollinating, or fertilizing, them. This permits the plants to produce their fruits and seeds. The bees’ greatest value by far is as pollinators of plants.

The Sting and Other Defences

A female bee has an egg-laying device (ovipositor) located at the end of its abdomen; the ovipositor also serves as a weapon and can inflict a painful sting. The bee’s sting has no food-capturing function. It has come to be used for defence against animals and humans that raid their honeycombs, and against robber bees and parasitic bees attempting to enter their nests.

Most bees can sting many times, but a honeybee worker has a tiny, hook-shaped barb that is caught inside the victim. This bee cannot fly away without tearing out its ovipositor and some internal organs a fatal injury. After the dying bee has flown away, its poison sac and the muscles left attached to the ovipositor keep pumping poison into the victim. As soon as possible the sting should be removed without squeezing the poison sac.

Africanised honeybees, also called killer bees, are particularly aggressive. They are descended from African bees that were imported into Brazil in 1956. The imported bees escaped in 1957 and began to mate with European honeybees the kind found in most hives. Although the sting of one Africanised bee is no more dangerous than that of a European honeybee, the Africanised bees release a chemical when they attack that signals other bees to come and join the attack. These bees may swarm over great distances in pursuit of a raider of their hives, and they have been known to attack in such numbers as to kill farm animals and humans. Since 1957 they have been moving steadily northward, and the first swarm entered the United States in October 1990.

Bumblebees sting when their nest is disturbed, but they are not easily aroused when they are gathering nectar. Sweat bees, attracted by perspiration, may alight on a person’s skin in summer. Their stings are sharp but not as painful as those of the honeybee.

Tropical sting-less bees defend their colony by crawling into the eyes, ears, and nose of an animal or under the clothing of a human raider. They bite, and create unpleasant sensations because of their sheer numbers. Some species secrete a caustic chemical that burns the skin.

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Posted 2012/02/15 by Stelios in Education

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BEES (Part 2 of 3)   Leave a comment

Nesting and Life Cycle

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

Bees vary greatly in nesting practices, depending upon the species. They may be classified as social bees, solitary bees, and parasitic bees (also called guest bees or cuckoo bees).

Social bees are members of colonies in which they cooperate with others to build the nest and to feed and protect the young. Colonies may contain as few as ten or as many as 80,000 bees. There are two kinds of females among the social bees, and they look quite different. The sexually mature, fertile females, called queens, are long and slender; the sexually undeveloped females, called workers, are small and chunky. The workers become their mother-queen’s helpers as housekeepers, nurses of the young, builders, guards to keep intruders from the nest, and foragers for food.

Only about 500 species of the more than 20,000 species of bees are social. They include honeybees, bumblebees, and tropical sting less bees.

Solitary bees care only for themselves and their immediate brood. Each female makes her own nest and cares for her offspring. The vast majority of bees are solitary, including leaf cutter bees, mining bees, and carpenter bees.

Parasitic bees, or guest bees, have no body parts for collecting pollen and do not feed or care for their offspring. They sneak into the nests of related species of bees to lay their eggs. The larvae that develop from these eggs are not welcome guests, because they often have huge jaws and use them to kill the larvae of their hosts. Parasitic bees are sometimes called cuckoo bees because, like the European cuckoo, which is a bird, they lay their eggs in the nests of others. Many species of sweat bees are parasitic.

During its life each bee undergoes a complete metamorphosis in four stages: egg, larva, pupa, and adult. The average bee egg is a tiny white sausage-shaped object about 14/100 inch (3.5 millimetres) long. From it hatches the larva, a white worm like grub with no eyes and no legs. After spending two or three weeks eating in its cell, the grub becomes less active as it enters the pupal stage. In some species the grub first spins a cocoon around itself before becoming a pupa. While outwardly still, inwardly the pupa is transforming into the adult bee.

The sex of the bee in most species is determined by whether or not the egg is fertilized. Fertilized eggs develop into females, infertilized ones into males. Male bees are called drones. They do no work and exist only for the possibility of mating with the females.

Honeybees

For at least 4,000 years honeybees have been kept for their honey and for beeswax, a tallow-like substance used to make candles, polishes, ointments, and many other products. Of great economic importance in most parts of the world, honeybees are native to Europe, western Asia, and Africa. They are also widespread in North America, where they were brought by the early white settlers.

The honeybees have a definite caste system; they are divided into three groups within the hive the queen, the workers, and the drones. The task of the queen is to lay eggs. The drones are males that can mate with the queen. The workers are female bees that do not lay eggs but do all the work necessary for the upkeep and protection of the hive.

Although bee keeping (also called apiculture) has been practised for many centuries, bees are not truly domesticated in the sense of being tamed. Those living in man-made hives behave no differently from those living in nests they make themselves.

In the wild, worker bees seek out a sheltered place such as a hollow tree or log, a cave, or a crevice in a rock or a building. Or they may choose to hang their nest from a tree branch. Using wax secreted between scale like plates on the underside of their abdomens, they build clusters of cells called combs. In the wild, combs may be somewhat rough and irregular, but each cell of the comb is a precisely shaped, six-sided tube open on one end. Two blocks of cells are placed back to back, forming a two-sided, or double-edged, comb. The comb hangs vertically with the open ends of the cells facing out the sides. To keep the larvae, which develop within, from falling out, cells are constructed with a slight upward tilt.

Bee keepers provide their colonies of bees with wooden boxes that are called hives. Inside the hives the bee keepers hang sheets of wax in wooden frames for the bees to use as foundations in building their combs. Ten or twelve of these frames can be hung side by side in each hive box.

As is the case in all colonies of social bees, the only sexually mature female honeybee is the queen. When she flies away from the nest to mate, she gives off an odour (a pheromone) that the drones find irresistible, and they follow her. The streamlined queen flies faster and higher than the majority of the short, stocky drones. As she soars upward, many of them give up the pursuit. From the few drones that can follow her as she continues on a rising, whirling flight, she chooses one to couple with. After mere seconds her mate falls dying to the ground, and she chooses another. Several drones in succession may meet the same fate before the queen returns to the nest alone. She never leaves the nest again, unless she moves with a swarm of worker bees to a new home. Fertile until shortly before she dies, she lays up to 2,000 eggs per day, one to a cell. The cells in which future workers and drones develop are similar and ordinary. But for the egg and larvae that will develop into a new queen, the cell must be enlarged. It usually resembles a peanut shell hanging from the comb.

Three days after it is laid, an egg hatches into a tiny larva. At first all larvae are fed royal jelly, or bee milk, a thick whitish nutritional substance that young worker bees regurgitate into the cells from a pair of glands. But only the future queens are kept on this diet. Future workers and drones are switched to beebread, made from pollen.

In about six days a larva grows to the size of an adult bee, filling its cell. Then a worker caps the cell with wax, and the larva inside spins a silk cocoon and becomes a pupa. In about 12 days the process of changing into a winged adult is at last completed, and the new bee emerges.

Newly emerged workers usually stay in the nest or hive for a time, first helping to clean out used cells, and then, when their glands begin producing royal jelly, feeding the larvae. At 10 to 16 days old the workers can secrete wax, which is softened by chewing and used to repair and construct cells.

Once the young worker’s wax glands stop producing, its job is to receive the nectar and pollen brought into the nest by older workers and to store it in the cells. By the age of 20 days the young worker may become a guard at the entrance to the nest. Eventually it leaves the nest to begin its lifelong career of foraging for nectar, pollen, water, or propolis. Propolis, also called bee glue, is a sticky resin from the buds of trees; it is used to repair cracks in the nest or hive and to cover the bodies of such intruders as moths, mice, or lizards that have been stung to death.

The division of work assignments in a hive is not rigid. Older bees may spend time at the nest or in the hive, eating and resting. They can reactivate their appropriate glands if young bees are few and the needs of the hive require more workers inside. A worker may live several months, but when there are empty cells and much nectar to be gathered she may work very hard and die in only six weeks.

Clustering and swarming. In the autumn the workers usually drive the drones away to starve or freeze. When winter arrives in cooler regions, all members of the honeybee colonies that nest in the open will die. But hive bees and those that nest in a sheltered spot can live through the cold weather by clustering. The bees of the colony huddle close together and form a ball around one of the combs. By moving their legs, wings, and bodies, the bees on the inside of the ball manage to keep warm, protected by the bees on the outside. And when the bees on the outside become cold, they change places with some of the bees on the inside. In extremely cold weather temperatures inside a cluster may be as much as 100° F (55° C) higher than outdoors. The cluster moves slowly as a unit over the combs so that the bees can eat the honey they have stored. Once midwinter is passed, the queen begins laying her eggs inside the cluster, starting a fresh colony.

When an old nest becomes crowded or a new queen emerges, honeybees may start a new colony by swarming. The old queen leaves the nest with a swarm of half the workers. Forming a dense throng around the queen, the swarm may hover in a tree while a few scouting workers seek out a suitable location for their new nest. If no new queen has emerged at the old nest, the workers remaining there rear larvae to be new queens, and the first one to emerge as an adult kills the others in their cells with her sting. The new queen quickly mates and begins laying eggs in 12 days.

Posted 2012/02/15 by Stelios in Education

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BEES (Part 3 of 3)   Leave a comment

Dance of the honeybees. A worker honeybee lets the other workers know about a new source of food it has discovered by rapidly vibrating its wings and performing a dance. When it returns to the nest, it first gives the others a sample of the nectar. From this, and from the scent on its body, they learn what kind of food the worker has found. That bee then performs a dance on the surface of the comb to show the others how far and in what direction to go to find the new food source.

The speed of the dance and its length can communicate the relative ease or difficulty of the flight: uphill or against the wind takes more energy. If the amount of food to be found there is great, the dance lasts longer and is more enthusiastic. Therefore, it arouses a greater number of bees. The number persuaded to go there will be proportionate to the amount of food to be found.

Bumblebees

Bumblebees are found throughout much of the world, primarily in the temperate and northern regions. In the spring a young bumblebee queen seeks a place suitable for building her nest. It may be a hole in the ground, a small pile of grass or debris, or the abandoned nest of a bird, mouse, ant, or termite. Using wax secreted from her abdomen, she makes a honeypot and fills it with nectar from flowers. Then she makes a cell, lays a few eggs in it, seals it, and sits on it like a brooding hen.

In three to five days her eggs hatch into four to eight grub like larvae. She may open their cell to feed them from the honeypot, or in some species the larvae eat through an opening from their cell into the honeypot. They eat and grow for about a week, and then each larva spins a silk cocoon and becomes a pupa. In two more weeks newly formed bees, pale, weak, and wet, crawl out to feed at the honeypot. In a few days they are bright and fluffy and can help care for the new larvae that their mother has been tending in newly built cells. Later they begin to forage for food, leaving the queen free to concentrate on laying eggs and adding more cells to form a rough comb. She uses the empty cocoons in her construction, strengthening them with wax. In hot summer weather bumblebee workers fan with their wings to cool the brood, and their buzzing can be heard at a distance.

In late summer, after the queen has raised many workers to feed the young and to forage, new young queens and drones are also raised. Some males develop from infertilized eggs laid by the queen, but most hatch from eggs laid by workers. The drones seek out the new queens and mate with them on the ground or in the air near it.

In the fall the old queen stops laying eggs, and when the weather turns cold, she dies along with all her workers and drones. The mated young queens leave the nest to find a sheltered place to hibernate, usually in the ground. When spring comes, they will emerge to seek suitable places for building their nests. Thus the cycle is repeated.

Tropical Sting less Bees

Commonly kept for their honey, tropical sting less bees are widespread throughout Mexico and in Central and South America. A few are found in tropical Africa, Asia, and Australia.

Bee keepers provide these bees with sections of hollow log for their nests and they plug the ends of the log with clay. To obtain the honey a plug is removed, and the whole nest may be taken out, crushed, and the honey strained.

Worker bees construct the combs of cerumen, a mixture of wax and plant resin. Most species of tropical sting less bees build inner walls of thin, paper-like cerumen that contain a number of tiny holes as passageways inside the nest. Some species construct long entrance halls. Remodelling of the nests goes on continually. Used cells are rebuilt; walls are moved; and the locations of entrances are changed so that additions can be made to the comb. Unlike the honeybees, who hang their combs vertically with the cells opening on the sides, the tropical sting less bees arrange their combs horizontally with the cells opening at the top. Some combs resemble a spiral staircase, while others are irregular clusters of many-sided cells.

Tropical sting less bees form social units that are in many ways as complex as those of honeybees. Some species have a dance similar to that of the honeybees, providing directions for flying to a source of food. Other species, during their return trip to the nest from a good food source, will light repeatedly and rub scent from glands on their jaws, marking an aromatic trail the other bees can track back to the source.

Solitary Bees

Most bees are solitary. They have no caste system and do not cooperate with others in building nests and providing for the young. Each female can mate and lay eggs, and each makes her own nest of cells. However, they often live as close neighbours to others like themselves, and they sometimes share the same hole in the ground as an entrance to separate nests.

After mating, the female bee makes a small nest, usually in the ground, often digging her tiny entranceway either vertically or horizontally into a bank of soil. Inside the nest she digs a cell, or makes one of wax, wood, or other material, and lays an egg in it. She then gathers pollen, puts it in the cell with the egg, and closes the cell. When the egg hatches, she will be gone, but her larva will be provided for. The female bee may make several more cells and stock them in the same way. She then seals them before she leaves the nest to die. Both female and male larvae eat their provisions and become pupae. They emerge as adults, fly away, and seek mates. The young mated females in turn will make their own nests.

Leaf cutter bees are found throughout the world. The female bee searches for a convenient, ready-made space in such places as a hollow stem, rotten wood, or the ground. There she shapes her nest in the form of a long tunnel. She constructs a cell, using circles she cuts from the leaves of shrubs such as roses or other plants. She begins by cutting a circle for the end of the cell. Next she cuts a series of oval pieces for the side walls. When the cell is made, she stores a mixture of pollen and honey inside, lays an egg, and finally closes the cell with a perfectly fitted disk of cut leaf. Then she begins the sequence again, constructing another cell in the same way, and continues her activities until the nest is filled.

Mining bees tunnel into soil or clay banks. The bee begins her nest with a long corridor, which she lines with clay moistened with regurgitated water. Short hallways lead off the main corridor to the nursery cells. The bee then fills the cells with nectar for her future young and lays an egg on top.

Carpenter bees bore into plant stems or even into solid wood buildings, fences, or posts. They then make their nests in the tunnel.

Classification

Hymenoptera, an order of insects having four membranous wings and mouth parts fitted for both chewing and sucking; includes bees, wasps, ants, sawflies, and ichneumon flies.

The more than 20,000 species of bees belong to a super family called Apoidea, of the order Hymenoptera, which includes ants, wasps, and hornets. They are one of the large class of Insecta of the phylum Arthropoda (invertebrate animals with jointed legs and segmented bodies).

Megachilidae, family of bees including leaf cutter bees, some sweat bees, and some parasitic bees.

There are three important and large families of bees. The Apidae, small to large bees found throughout the world, includes all social bees (honeybees, bumblebees, and tropical sting less bees), carpenter bees, and some mining bees. Most honeybees native to Europe, Africa, and the Middle East have the genus and species name, or scientific name, Apis mellifera. Most honeybees native to India, Indochina, and Japan are Apis cerana. Bumblebees are of the genus Bombus, which has about 200 different species. The Megachilidae family, medium to large bees found throughout the world, includes more than 1,000 species of leaf cutter bees, some sweat bees, and some parasitic bees. The Halictidae family, small bees found throughout the world, includes some of the sweat bees.

Posted 2012/02/15 by Stelios in Education

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WASPS – any of various families of winged hymenopteran insects   Leave a comment

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.

Posted 2012/01/12 by Stelios in Education

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ANIMAL BEHAVIOUR (Part 2 of 3)   Leave a comment

Orienting Behaviour

An animal orients by adjusting its posture and position in space. It does so in relation to the source of different forms of energy in its environment. These forms include light, heat, and chemicals in the air or water, pressure, electric current, air or water currents, gravity, radiation, and magnetic fields.

Tropism, involuntary turning of a cell or organism in response to a stimulus.

Orienting behaviour may take the form of a tropism an action in which the animal simply orients its body toward or away from the source of energy without changing location. Plants can also respond in this way. However, the orienting response may take the form of a taxis a movement toward or away from the source of energy by swimming, flying, or locomotion. As a rule, only animals are capable of such responses. Still another type of orienting response is called a kinesics an increase or decrease in an animal’s activity, but in no particular direction.

Prefixes are usually added to the root words tropism, taxis, and kinesics to indicate the kind of energy to which the organism is responding. For example, geotropism is response to gravity; photo taxis, response to light. Prefixes may also indicate the type of response made. Thus klinokinesis refers to turning activities. In addition, the direction or intensity of a response may be described as positive, if directed toward a stimulus, or negative, if directed away from it.

Orientation makes it possible for an animal to feed, to exhibit social behaviour, and to avoid obstacles and barriers. Some organisms, such as the bat, use sonar reflected sound to locate prey and to avoid obstacles. Some fish can navigate through tight crevices by detecting changes in their electric field. Electronic instruments enable researchers to detect and record the sound frequencies and electricity emitted by different species.

When foraging for food, the honeybee orients to the odour of flowers and the polarization of light. It also responds to cues from the sun’s position off the horizon. This type of activity is called sun compass orientation. On returning to the hive the bee performs certain “dances” a variety of motor patterns that vary with the distance and direction of the food. These dances stimulate the other bees to travel the path of the returning bee.

Fish and birds also exhibit compass orientation when homing or migrating. However, scientists are not sure that animals navigate in the same way as man. When humans navigate, they use such instruments as the sextant to find the altitude of the sun and stars and a chronometer for timekeeping. It has not yet been demonstrated that homing and migrating animals can “shoot an azimuth” and “tell time.”

Some animals are known to return to the areas where they were born or spawned. The salmon, for example, upon reaching sexual maturity responds to the chemical characteristics of the stream in which it was spawned. The hormonal changes associated with sexual maturity are a cause of this new sensitivity. The stickleback moves from salty to brackish water to reproduce. Its behaviour is related to endocrine gland responses to seasonal fluctuations in light. Similar hormonal changes in birds lead to migration and reproduction. These cyclic changes in behaviour due to hormonal regulation are considered evidence of a chronometer that might enable migrating or homing animals to correlate changes in visual cues during compass orientation with changes in internal rhythms and thus make navigation possible.

Social Behaviour

All living things relate to other members of their species. In an amoeba, the relationship occurs only during the short time it takes the animal to split into two animals. In other species, such as the social insects, the relationship is so necessary that they cannot survive as individuals. This is true also of humans, who are dependent on others until they reach maturity. Social organization of some kind is common to all animals. However, the type of organization varies with the nervous system of the species. And in true social organization, animals of the same species react to each other.

Con-specifics, or animals of the same species, may at times be close to each other without exhibiting social behaviour For example, mollusc larvae may respond to changes in the intensity of light by swimming to the water surface. The resultant grouping, called an aggregation, stems from a common response to a physical aspect of the environment. But a response is truly social only when it is a response to visual, chemical, auditory, or other stimuli emanating from a con-specific As a result of such stimuli, animals may approach each other to form a bond or to fight. Although dissimilar, both reactions are examples of social behaviour

Goby, any of numerous, widely distributed, spiny-finned fishes constituting family Gobiidae, having wide, flat head, large mouth, and ventral fins often united in funnel-shaped disk.

The type of bond formed by con-specifics is a measure of their nervous and hormonal systems. Organisms with relatively simple systems may respond to each other only as long as they give off attractive or offensive stimuli. For example, a worm will approach another worm during the reproductive state because certain chemicals are released. Once mating has occurred, they have nothing further to do with each other. A goby will remain near its eggs only as long as the hormonal state of the fish and the chemical and visual features of the eggs remain the same. Once the fry, or young, hatch, the fish responds to them as it would toward any small fish and tries to eat them. The goby does not recognize the fry as its own offspring.

Although orientation, changing hormonal levels, and other processes play a part, social bonding depends primarily on a mutual exchange of stimulation and food between animals. The give-and-take stimulation of a pair or a group is fundamental to the organization of social groups.

The Army Ant Colony – An Example of a Social Group

An army ant colony consists of many thousands of workers and a queen. The queen is capable of laying large batches of infertile eggs when she is fed sufficiently. These eggs hatch into workers, females incapable of sexual reproduction. However, at a certain stage of the queen’s development she produces a brood of males and females capable of reproducing and starting new colonies.

The colony has a two-phase cycle of activity. The nomadic phase lasts about 18 days. By late afternoon or early evening, the larger workers cluster and leave the bivouac area where they spent the previous night. They move out over many yards in the area around the bivouac. As they crawl, they lay a chemical trail. Other ants in the colony travel over the trail, and as the trail becomes more frequently travelled the concentration of chemical stimuli on it becomes stronger. The entire colony, queen and all, eventually move out from the bivouac along the trail. The ants range over large areas, preying on other insects and their young.

Army ants take in considerable food during the nomadic phase. The queen receives a good deal of it. She does not usually forage but is able to feed on the food brought back by medium-size workers. They return to the bivouac to lick the queen for the highly attractive chemicals she exudes. Chemicals that attract or repel con-specifics and heterospecifics (members of other species) are called pheromones. The exchanges of food and secretions between the queen and the workers produce a strong social bond that aids in keeping the colony together. The queen’s increased food intake enables her to lay a batch of eggs. However, this affects her relationship with the workers. She becomes less stimulating to them, and their foraging, therefore, begins to decrease. Now the colony enters the other phase of its cycle the statuary phase. The number, frequency, distance, and area of foraging decreases considerably. The level of the entire colony’s activity drops to a minimum.

After about 21 days the eggs hatch, and the larvae emerge. These squirming, active young are an intense source of stimulation to the workers. The workers are driven out of the bivouac and the nomadic phase starts again. They are now attracted by the pheromones of the larvae and the queen. When the workers return from foraging, they drop their food and feel and handle the larvae with their antennae and legs. As a result of this excitation, the number and frequency of raids again increase. The colony travels great distances, the larvae are fed, and the queen is overfed. At this point, the colony consists of the queen, workers, and larvae.

About 18 days after the eggs have hatched, the larvae enclose themselves in cocoons and become pupae. At about the same time, the queen lays her next batch of eggs. Now the colony consists of the queen, workers, pupae, and developing eggs. However, the pupae and the eggs offer little stimulation for the workers, and the statuary slowdown begins. But the queen continues to secrete pheromones that socially bind the colony.

Dominance

In communities of certain animals the ruling, or dominant, animal is the largest, strongest, or most aggressive and thereby exerts the most influence on the other animals in the group. The dominant animal enjoys the greatest and most preferential access to members of the opposite sex and control of the best territory for feeding and breeding. Many groups of animals, most notably baboons, birds, foxes, lions, and crocodiles, establish dominance hierarchies. The best-known example is the pecking order of chickens. Flock members are arranged on the “rungs” of a social ladder, with each chicken superior to those below and subordinate to those above. The top animal has primary access to the necessities of life, such as the best food, mates, and living quarters. Submissive animals are left with less-desirable food, mates, and living quarters. Such animals may even be expected to groom dominant members and to help care for the offspring of more dominant animals, because subordinates are often prevented from having offspring of their own.

In other animal groups, dominance hierarchies are more complicated. Wolf packs, for example, are led by two dominants who have three subclasses of subordinates below them. Other animals have only one dominant leader with all other animals below him or her being exactly equal. Once an animal has established dominance, challenges to the order are rarely made from within the group, since animals are reluctant to fight other animals that are bigger, stronger, or more aggressive than they are themselves. Sometimes, however, animals from outside the group can successfully challenge and overthrow a long-time leader, but this is rare.

In more intelligent species, such as baboons, factors beyond mere size and strength determine the dominance hierarchy. Age seniority, hormonal condition, maternal lineage, and personality are sometimes factors that affect dominance in more intelligent animals. In baboon groups, furthermore, hierarchies are often elaborate. Adult males are dominant over less mature males and females; yet a fully mature female can be dominant over a less mature male. A dominant baboon displays its superiority with rapid “fencing” manoeuvres, open-jaw displays, and hitting.

Close Bonds Among Animals

Animals with complex nervous systems, ranging from some fish to mammals, may form monogamous bonds. The mates of such species stay together for a breeding season or even for a lifetime. Their social ties are not restricted by the time-bound, immediate stimulation that simpler animals need. However, monogamous pairs must be able to identify their mates from other con-specifics This requires the intricate action of an advanced nervous system.

Some birds and many mammals band in large groups, such as herds and families. These groups include adult males and females and offspring of different ages. The offspring in most mammalian groups remain with the group until they reach sexual maturity. The females frequently remain until the group splits up. Some socially bonded groups of mammals consist of an older male, a number of younger males, many females, and immature offspring. Among the howler monkeys and some other mammals, the younger males band together into a marginal bachelor group until each establishes himself as the older male in a new social group.

Not all mammals maintain elaborate group arrangements. Many live fairly solitary lives, coming together only for mating. Afterwards, the female remains with the litter until the young become juveniles or are sexually mature. In some instances, the mating pair stay together until the young are born. Beavers behave in this way. In other instances, the male and the female separate immediately after mating. This is true of many other rodents.