Archive for the ‘MOSQUITO’ Tag

MOSQUITOES   Leave a comment

DEFINITION: any of a large family (Culicidae) of two-winged dipteran insects, the females of which have skin-piercing mouth parts used to extract blood from animals, including humans: some varieties are carriers of certain diseases, as malaria and yellow fever.

More than just annoying insects, some mosquitoes are responsible for transmitting diseases that can result in serious illness and even death. Mosquitoes were once viewed merely as a nuisance because of the itching and irritation that resulted from their bites. In the early 1900s, however, they were recognized as carriers of yellow fever, malaria, and other diseases.

The mosquito is in the family Culicidae and belongs to the same order of insects as flies and gnats the order Diptera and has the same anatomical structure. Its soft body is covered by an exoskeleton (an external supportive covering) and divided into three parts: the head, thorax, and abdomen. It has two narrow wings and a pair of knob-like structures, known as halters, that are present in place of a second pair of wings. Unlike other Diptera, the wings of the mosquito have tiny scales on the veins.

The mosquito’s head is rounded and supported by a slender neck. It has large compound eyes, complex mouth parts, and two antennae, usually divided into 15 segments. The antennae of the male are more feathery in appearance than those of the female. The major body segment behind the head is called the thorax, to which the wings and six legs are attached. The legs are long, slender, and segmented. The final segment of the mosquito’s body is the soft, cylindrical abdomen. It has ten segments, the last ones bearing the openings for the anus and reproductive organs.

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

The most dangerous parts of a mosquito’s anatomy are the female’s mouth parts These are modified into a proboscis for piercing and sucking. The proboscis looks like a single thin tube and is straight in most species. It actually consists of a sheath (the labium) that encloses saw-tipped daggers (the mandibles and maxillae), an injection tube (the hypopharynx), and a sucking tube (formed by closing the labium against the hypopharynx). The construction of the proboscis is ideal for removing blood from beneath the skin of animals. The mouth parts of the male mosquito are modified for feeding on plant juices; male mosquitoes do not bite.

Mosquito Bites

Not all species of mosquitoes suck blood. However in some species a blood meal by the female is essential to the reproductive cycle. In most species the females, like the males, suck nectar and other juices from plants for nourishment. The bloodsucking species feed primarily on mammals or birds, though some mosquitoes will feed on reptiles and amphibians. Some species are particular in their choice of host species, whereas others appear to be less selective. The feeding periods of many types of mosquitoes are restricted to particular times of the day or night.

To obtain a blood meal, a female mosquito selects a likely spot on her victim, brings her labium against it, and begins sawing through the skin with her mandibles and maxillae. Through her hypopharynx she injects saliva into the wound to prevent the blood from clotting so that it flows freely into her labro-hypopharyngeal tube. She then sucks up a supply of blood, stores it in her abdomen, and flies away.

The itching of a mosquito bite is caused primarily by the saliva that has been injected. If the mosquito completes her withdrawal of blood before being driven away, much of the saliva will be removed and the itching may be less severe.

Life Cycle and Habitats

A mosquito’s life cycle is one of complete metamorphosis it consists of four distinct stages: egg, larva, pupa, and adult though the pattern of development may vary between species. The female mosquito typically lays her eggs in standing water, where they float on the surface in a tiny cluster. The eggs may also be deposited singly or attached to vegetation, depending upon the species of mosquito. Some mosquitoes lay their eggs in the vicinity of water rather than directly in water, and the eggs develop when the area becomes flooded.

During warm weather the eggs develop into larvae within two or three days. Mosquito larvae are long, transparent, and constantly wriggling as they move up and down in a water column. They feed on organic matter, including small animals, bacteria, dead plant material, and algae. Some species feed on other mosquito larvae.

Pupa, quiescent stage between larva and adult in insect metamorphosis.

As the larvae grow, they periodically shed their skins (called moulting) in order to accommodate their larger bodies. Mosquito larvae normally moult four times. After the final moult the animal emerges as a pupa. The pupa has an enlarged anterior portion, composed of a head and thorax, and a curved, elongate abdomen. The pupa is aquatic but does not feed. Both the larvae and pupae of most species must come to the water’s surface to breathe. After two or three days the pupa develops into an adult, emerges from its pupal case, and flies away.

Mosquitoes vary in their courtship and mating habits. Many species mate while in flight. The males of some congregate in huge swarms, to which the females are then attracted. The humming sound made by mosquitoes is often a signal to attract mates.

In cooler temperate regions, adult mosquitoes hibernate, emerging in the spring to lay eggs. In some species mating occurs before the approach of winter and the males die, leaving only fertilized females. In others, eggs are laid in the fall and survive the winter without harm to hatch in the spring.

Mosquitoes are found almost everywhere in the world except open ocean areas, the most arid deserts, and the polar regions. Because of their dependence on water for development during their first stages of life, mosquitoes are most abundant in wet regions of the world. Nevertheless, of the more than 150 species of mosquitoes that inhabit the United States, many persist in arid regions of the South west Some species thrive in the extremely cold climates of Canada and Alaska, where vast swarms can sometimes be seen around some of the larger lakes and marshes.

Mosquitoes live in a wide variety of aquatic habitats. Besides lakes, ponds, and marshes, some mosquitoes lay their eggs in small depressions where water has collected temporarily. For example, many species use tree holes or fallen leaves, where water has accumulated after rains. In urban areas, common egg-laying sites for mosquitoes are empty containers that have collected water. Furthermore, mosquitoes are not restricted to fresh water for egg laying salt marshes are also a common habitat of many species.

1902: Cure for yellow fever. Walter Reed was a physician and bacteriologist in the service of the United States Army when he proved that yellow fever is transmitted by mosquito bites. Throughout the 19th century the general assumption was that yellow fever was transmitted by contact with such articles as clothing or bedding touched by someone who had the disease.

A Cuban doctor, Carlos Juan Finlay, theorized that the disease was carried by insects, but he had not been able to prove it. In 1896 an Italian scientist, Giuseppe Sanarelli, isolated the organism Bacillus icteroides from yellow fever patients. Reed, along with physicians James Carroll and Aristides Agramonte, was assigned the task of investigating the bacillus. At the same time, a yellow fever outbreak started in the American military garrison in Havana, Cuba. The three travelled there in the summer of 1900 and, by 1902, proved that mosquitoes were the carriers of the disease.

Shortly afterwards an insect extermination program was undertaken, and Havana was freed of yellow fever within 90 days. Colonel William Crawford Gorgas of the U.S. Army Medical Corps later used Reed’s techniques to rid Panama of yellow fever, making way for the construction of the Panama Canal.

Mosquitoes and Disease

Mosquito-transmitted diseases differ in their geographic distribution, specific causes and effects, and in the types of mosquitoes that transmit them. Yellow fever is caused by a virus that is transmitted primarily by the mosquito species Aedes aegypti, found in tropical and warm temperate regions of Africa and the Americas.

The primary mechanism of transfer of the yellow-fever virus (as well as other disease-causing organisms) is the mosquito bite specifically, when a mosquito bites an infected person and then bites a healthy one. The virus is thus passed from one person to another through the fluids from the mosquito’s mouth. The yellow-fever virus can also be present in other mammals, including monkeys, armadillos, and rodents, and a mosquito can transmit the disease to humans after biting an infected animal. Yellow fever attacks the liver, kidneys, and digestive tract, producing high fever and jaundice, a yellow skin colour from which the disease gets its name. More than half of the victims of yellow fever die within a few days. Those who recover are immune thereafter.

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

Malaria is another disease transmitted by mosquitoes. It is caused by microscopic protozoan parasites of the genus Plasmodium. The transmission of malaria is more complicated than that of yellow fever because the parasite must spend a portion of its life cycle inside a mosquito and the other part inside a human. (Yellow fever is dependent on the mosquito only as a transmitting agent.) Malaria is transmitted by mosquitoes in the genus Anopheles.

When an Anopheles mosquito bites a person infected with malaria, it may ingest blood that contains parasites in the sexually reproductive stage, called gametocytes. These gametocytes unite in the mosquito’s digestive tract and produce egg-like cells that burrow into the intestinal wall. They then hatch into free-swimming forms that travel to the mosquito’s salivary glands.

When the mosquito bites an uninfected human, the free-swimming parasites are transmitted to the victim through the mosquito’s saliva. These tiny parasites then enter the victim’s red blood cells and begin to divide to form new parasites. Eventually, the affected blood cells burst, and the parasites are released to enter new blood cells within the host and repeat the process of growth and division.

Within one to two weeks millions of these parasites are being released from burst blood cells, resulting in the characteristic symptoms of malaria: periodic chills and fever. Within ten days to two weeks after the initial infection, a new generation of sexually reproductive parasites develops in the blood of the victim. These parasites produce gametocytes, and victims can then infect any Anopheles mosquito that bites them. In this way the cycle of the disease is perpetuated.

In many areas of the world, including North America, mosquitoes of the genus Culex are transmitters of viral encephalitis (sleeping sickness) and other diseases. Dengue, or “break bone fever,” is a common tropical disease that results in muscular pains and eruptions of the skin. It is transmitted by Aedes and Anopheles mosquitoes.

Filariasis, disease caused by roundworms and transmitted by mosquitoes.

Roundworm, worm of the phylum Aschelminthes and the class Nematoda.

Filariasis, a disease that affects the lymph glands, is caused by parasitic roundworms and is transmitted by several different mosquito species in tropical regions.

Mosquito-transmitted diseases can be controlled through the elimination of mosquitoes or their egg-laying sites, medical treatment of victims, and prevention of mosquito bites through the use of insect repellent or protective clothing. As early as the 1700s South Americans recognized that quinine, an alkaloid obtained from the bark of the cinchona tree, alleviated the symptoms of malaria, though they did not know how the disease was transmitted.

In the late 1800s mosquitoes were implicated in the transmission of yellow fever in Cuba, and in the transmission of malaria in India. The United States Army initiated the first major effort to eradicate a mosquito-transmitted disease when it launched its campaign to quell the Cuban yellow-fever epidemic. Once the relationship between mosquitoes and yellow fever was understood, major projects were undertaken to eliminate the egg-laying sites of the Aedes mosquito. Similar measures were taken in malaria-infested areas of the world.

In addition to eliminating mosquito habitats, large-scale production began of chemical products that would kill mosquitoes or their eggs. Aerial sprays have been developed to kill adult mosquitoes. Toxic chemicals and oil products have been used in aquatic habitats to kill mosquito eggs, larvae, and pupae. Such chemicals must be used with caution because of their potentially damaging environmental effects. Mosquito bites can be prevented effectively with the use of a wide variety of insect repellents.

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

Posted 2012/04/29 by Stelios in Education

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PEST CONTROL   Leave a comment

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

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

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

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

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

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

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

Chemical Control

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

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

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

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

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

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

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

Biological Control

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

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

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

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

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

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

Other Controls

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

Crops are sometimes protected from harmful pests through diverse planting techniques. Crop rotation, for example, prevents the development of fungus and bacterium populations. Open-area planting relies on the wind to hinder flies and other insects that damage vegetable crops.

Physical or mechanical control methods are effective against some pests. Such controls include sticky barriers, heat killing (for storage pests), and flooding (for ground pests). Pressure-treated wood is protected against many wood-damaging fungi and insects. Traps are another mechanical method of pest control. Some traps are designed to either kill or capture rodents and other vertebrate pests. Netting and metal shields are used to keep birds from damaging fruit crops or from roosting on buildings. Electrical light traps attract insects and electrocute them. In some buildings, fans are installed above doors to prevent the entry of flying insects.

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

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

Assisted by George W. Rambo.

FLIES   Leave a comment

DEFINITION:1 a) any dipterous insect; esp., the housefly b) any of several four-winged insects from various orders, as the mayfly or caddis fly 2 a hook covered with feathers, coloured silk, etc. to resemble an insect, used as a lure in fishing: a wet fly drifts below the surface of the water, and a dry fly floats on it 3 Printing a device on a flat bed press for removing and stacking the printed sheets.

While some flies are beneficial to humans as parasites of insect pests or as scavengers and many others are important as plant pollinators, flies are also known to be carriers of such serious diseases as cholera, typhoid, and dysentery. In most species of fly the body and padded feet are covered with bristling hairs and the tongue is coated with sticky glue. Under a powerful microscope, samples of the dust and dirt clinging to these hairs reveal bacteria that cause a wide variety of diseases. Flies get the germs from garbage and sewage. If they touch food later, it too may become contaminated.

Flies can multiply at an incredibly fast rate. Between the months of April and August one female fly could have more than 190 quintillion descendants if all her female offspring and their descendants lived. Although this does not happen, plenty of flies will be produced every summer if only one female in a hundred escapes death long enough to lay eggs. The only effective way to keep down the number of flies is to prevent breeding.

Long exposure to freezing weather kills flies. In cold climates only a few fertile females hibernating in sheltered places survive the winter. Warm weather awakens them and they seek moist spots such as manure piles or garbage in which to lay their eggs.

Maggot, larva of an insect; term most often applied to larva that lives in decaying matter.

The eggs look like tiny white grains of wheat, about 1/20 of an inch (0.13 centimetre) long. The female lays up to 250 eggs in several clusters. Within 24 hours the eggs hatch into white larvae, or maggots. These feed and grow for about five days, then become pupae. Some five days later an adult fly emerges from the pupa case. In two or three days each new female is ready to lay eggs. The entire life cycle takes about two weeks to complete.

The Right Way to Get Rid of Flies

Once flies are established in a locality, they can be suppressed only by eliminating the places in which their eggs can hatch and the maggots can feed. If manure and garbage are removed from a location and destroyed regularly and if garbage cans are kept covered the population of houseflies in that location can be kept to a minimum. If this regular removal schedule is not possible, garbage can be kept in fly-proof containers of sheet metal or screening while awaiting collection. Manure piles can also be treated with suitable chemicals for example, calcium cyanamide and calcium super phosphate (acid phosphate) to keep them from attracting flies.

People can protect themselves from any surviving flies by putting screens on their doors and windows, by swatting, or by applying any of various chemical sprays or dusts, particularly those containing pyrethrum. Insecticides should be used with care to avoid contamination of food, dishes, and utensils.

The Physical Characteristics of Flies

The adult fly is about one-quarter inch (0.64 centimetre) long and about half an inch (1.27 centimetres) across the outspread wings. A thousand adults weigh less than an ounce. Each foot on its three pairs of legs is equipped with claws and two hairy pads called pulvilli. These pads secrete a sticky liquid that enables the fly to cling to almost any surface and run upside down along a ceiling.

A fly has five eyes. Two of these are huge compound structures that cover most of the head. Between these are three tiny simple eyes, set in a triangle. A flys vision, however, is not sharp. It relies more upon its acute sense of smell to locate its food.

The mouth parts are adapted for sucking up liquid food. A long “tongue” has two pads, or lobes, at the end, which act as funnels for drawing in liquid. The fly can also turn soluble foods such as sugar into liquids by spreading saliva on them. Unlike the bloodsucking sand flies, or stable flies (Stomoxys calcitrans), which they resemble, houseflies have no equipment for biting.

Some Relatives of the Housefly

Most two-winged insects (Diptera) are properly called flies. In place of the second pair of wings possessed by bees, dragonflies, and many other insects, true flies have club-shaped balancers (halteres). About 45,000 members of the order Diptera are known; some 11,000 are found in North America.

Stable fly, bloodsucking fly inhabiting stables; often enters houses.

Next to the housefly (Musca domestica), the most widespread and annoying members of the order are probably the mosquitoes. Some of these rank also among the deadly disease carriers. Sand flies, usually found in wet regions, transmit disease by biting. Another dangerous biter is the tsetse fly of central Africa.

Mediterranean fruit fly (or medfly), destructive insect (Ceratitis capitata); attacks fruit, nuts, and vegetables; yellow, black, and white markings; lays as many as 500 eggs in citrus fruits (except lemons and sour limes); larvae tunnel into the flesh of the fruit making it unfit for human consumption; discovered in Florida in 1929; thought to have been eradicated in the United States by 1930; reappeared in 1956 and in the early 1960s and again, in California, in 1981; worldwide quarantine laws were formed because of this pest to regulate the entry of fruits into countries; heavy U.S. infestation in 1981 set off heated controversy between fruit growers and environmentalists; the aerial-spraying program that was finally adopted sparked renewed debates worldwide about the eradication of costly insect pests.

Much damage is done by fruit flies in tropical and semitropical climates. Especially harmful is the Mediterranean fruit fly (Ceratitis capitata). The fruit fly called Drosophila melanogaster has proved extremely useful in studies of heredity. It passes through its life cycle in a few days. The results of selective breeding, of diet, and of other influences can be observed within a short time.

Midges, group of flies belonging to the order Diptera, family Chironomidae; mosquito like in form but more delicate.

Horsefly (also called gadfly), a two-winged fly of the order Diptera, family Tabanidae; usually about 3 times size of housefly; has pointed proboscis; only females suck blood; males sip plant sap or nectar.

Flesh flies breed and lay their eggs in stored meats; bot flies, or heel flies, torment cattle, sheep, and horses; gall gnats damage fruit. Other annoying or vicious flies are the tiny midges, including the “punkies,” or “no-see-ums” (Ceratopogon guttipennis), of the northern woods; the swarming black flies (Simulium hirtipes), which have been known to drive animals into fatal frenzies; horseflies, which also bite humans; and the so-called bee lice, bat ticks, and sheep ticks, which are parasites and so have lost their wings.

More useful members of the order are the syrphus flies, which resemble bumblebees and wasps and destroy plant lice; drone flies, whose larvae live in foul water, eating decaying vegetable matter; and robber flies, which consume other insects. Less-known members of the group are the louse flies, the nimble flies, the humpbacked flies, the March flies, and the false crane flies.

Flies are among the oldest of insects. Their fossil remains are found in rocks of early geologic ages and may also be preserved in ancient amber.

Posted 2012/02/08 by Stelios in Education

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