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.

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.

Bed bug

An organism that lives on or within another organism, called the host, and that gains its sustenance from the host organism is known as a parasite. Parasites occur among all the major groups of living things. There are parasitic fishes for example, the lamprey, which attaches itself to other fishes and sucks their body fluids. There are many parasitic arthropods, including fleas, lice, biting flies, and mosquitoes.

Many worms are parasitic. Some live in their host’s digestive tract and feed on the food that passes through. Some attach to the intestinal wall and suck the host’s blood. Some, such as those that cause trichinosis, enter the host through the digestive tract and then burrow into the tissues of the entire body. Some also parasitism plants.

Many fungi are parasitic. The rusts are fungi that are responsible for many diseases of major food plants. Parasitic bacteria are responsible for diseases ranging in severity from acne and tooth decay to such major plagues as the Black Death.

The viruses are unique in that they are all parasitic. They are the smallest of the parasites and may enter the host through the respiratory system or may be spread through sexual contact.

Characteristics

 As originally defined, parasites included any organisms that live by drawing food from a host organism. Defined in this broad way, parasitism included relationships that ranged from benign to harmful and even fatal to the host. The term parasitosis was later developed to describe those forms of parasitism that injure the host, and today the term symbiosis describes benign or even mutually beneficial associations between organisms.

Effects on the host. A parasite’s effect on its host is determined by various factors. Many parasites, for example, do not reproduce in their hosts, or reproduce only to a limited degree. Such parasites, including many parasitic worms, produce eggs that enter another host before they develop. The damage done by such parasites depends in part on the number of parasites in the host, known as the host’s parasite burden. Many hosts can carry a light parasite burden that is, they can support a small number of parasites and suffer no ill effects. A heavy parasite burden, however, may cause severe injury to the host.

In the case of parasites that may undergo unlimited reproduction in their hosts for example, the protozoans, bacteria, and viruses the factors determining the final effect on the host can be quite complicated. The ability of the hosts’ natural defences to destroy the parasites often plays a major role. Very young, old, or weak hosts that have limited defences may be severely harmed by large parasite populations that are able to develop unchecked.

Varieties. Parasites are commonly described in terms of their relationships to their hosts. Parasites that remain on the outer surfaces of their hosts are called ectoparasites. Parasitic arthropods are usually ectoparasites. Endoparasites are parasites that live within the bodies of their hosts. The various parasitic worms that live within the hosts’ digestive tracts are endoparasites. Many endoparasites actually dwell within the tissues of their hosts, not just in the cavities of the hollow organs. The bacterium Mycobacterium tuberculosis, the most common cause of human tuberculosis, lives within the cells of the lung tissues.

Bedbug, a small, flat, bloodsucking insect (Cimex lectularius), of reddish-brown colour, of order Hemiptera, family Cimicidae; is parasitic on humans.

Parasites may be permanent or temporary residents in or on their hosts. The bedbug is a temporary parasite. It crawls onto its host to feed and then returns to its hiding place, where it spends most of its life. The flatworm that causes a form of human schistosomiasis is a permanent parasite. Once it enters a host’s body, it remains there until it dies.

Some organisms can live either as parasites or as free-living forms; they are called facultative parasites. For example, the free-living protozoan Naegleria fowleri, which occurs in streams and lakes around the world, can cause infection of the brain after it enters the noses of swimmers. Other organisms, called obligate parasites, can live only a parasitic existence. Plasmodium falciparum, an organism responsible for a form of human malaria, is an obligate parasite.

Autoecious parasites are parasites that complete their life cycles within a single host. Many parasites, however, have quite complex life cycles and may require more than one host. In some cases the immature stages of the parasite develop in one host, and maturation and sexual development occur in a second host. Hosts in which the immature stages of the parasite develop are referred to as intermediate hosts. Parasites that require two or more hosts to complete their life cycles are referred to as heteroecious.

Malaria, disease consisting usually of successive chill, fever, and “intermission” or period of normality.

The pattern of having more than one host can sometimes provide parasites with a means of spreading. The protozoan that causes malaria has two hosts: humans and certain other animals, and anopheles mosquitoes. Asexual reproduction occurs in infected humans and animals, and sexual maturation, fertilization, and reproduction occur in infected mosquitoes. The protozoans depend on the mosquito to transmit them from one human host to another.

Methods of transmission. An organism that transmits a parasite, as the anopheles mosquito does, is called a vector. Vectors need not transmit parasites by biting, however. Some vectors transmit parasites when they are eaten by the hosts. Certain tapeworms that infect cats and dogs use fleas as vectors. When the cat or dog swallows a flea that is caught during grooming, the immature forms of the tapeworm emerge from the flea’s body and mature in the cat’s or dog’s intestine. The mature tapeworm produces numerous eggs that then pass out of the animal’s body with its faeces and contaminate the environment. If an immature, or larval, flea ingests the tapeworm’s eggs as it feeds on the infected faeces, it becomes infected in turn. The parasite’s life cycle is completed if the cat or dog catches and eats the mature infected flea. A situation such as this, in which a parasite (the tapeworm) is parasitic upon another parasite (the flea), is referred to as hyper-parasitism

Human Parasites

Parasitism in humans is widespread, but the type of parasite varies with geographic regions and social conditions. In areas where sanitation is poor, parasites that are spread by ingestion of faecal-contaminated food and water are common. In areas where housing is inadequate, parasitic insects may be common.

In parts of the world with adequate sanitation and housing, parasites transmitted by faecal contamination and biting insects are generally rare, but those transmitted by direct contact and through the respiratory system may still be common. The parasites that cause measles, mumps, and chicken pox, for example, can spread rapidly in crowded school environments.

Plant Parasites

Arthropod, animal of the phylum Arthropoda comprising invertebrates with external skeleton, segmented body, and jointed appendages.

In many respects the parasites of plants are similar to the parasites of animals. The arthropods, fungi, worms, bacteria, and viruses that parasitic plants may either grow on the plant’s surface or invade the plant’s tissues and, in the case of arthropods that suck plant fluids, may also transmit other parasites, particularly viruses.

Some plants have become parasites on other plants. The simplest form of plant parasitism is that in which the parasitic plant uses its host only for support. The strangler fig, a tropical tree that is grown as a common house-plant, slowly surrounds its host tree until the host dies. The fig then has access to the light above the forest canopy and can grow unhindered.

Other parasitic plants, such as the mistletoe, have a somewhat greater dependence on their plant hosts. Mistletoe grows on trees and uses them for support. In addition, though it makes some of its own food, the mistletoe sends modified roots into its host to draw out nutrients.

Dodder, a leafless parasitic plant introduced into U.S. from Europe with clover seeds; now a rapidly growing pest.

The most complete form of plant parasitism is that in which the parasite relies completely on the host for sustenance. Dodder, for example, is a parasitic vine that draws all its nutrients from its host.

Special Types of Parasitism

Entomologists, scientists who study insects, have described a type of parasitism in which one insect, usually a species of wasp, uses another insect to brood its young. This type of parasitism is called parasitoidism. The parasitoid wasp lays its eggs in or on the host insect, commonly a caterpillar. The wasp’s larvae develop inside the host, feeding on its body, and emerge as full-grown adults. Parasitoidism is being used by some farmers as a means of pest control. Various parasitic wasps, for example, are used to help control agricultural pests.

Another unusual form of parasitism is brood parasitism, which is common among certain birds, particularly the cow-bird and the cuckoo. In this form of parasitism, the parasitic bird lays its eggs in the nest of another species. The host bird then raises the intruder’s young as though they were its own.

A type of parasitism called social parasitism occurs among certain communal insects. Some species of ants, for example, kidnap and enslave the workers of other ant species.

Assisted by Julius P. Kreier, Professor of Microbiology, Ohio State University, and author of ‘Parasitic Protozoa’.