Gadfly Photo and description of the insect > Insects


Gadfly — a large parasite fly, about which you can hear many incredible stories, in particular about their terrible bites and larvae, which are not laid in the victim’s body. There are many misconceptions about habits, the lifestyle of these insects, and the main thing is that these large flies suck blood. In fact, adults are not blood-sucking — they do not eat at all during the entire period of their existence, but nevertheless can do much more harm.

Origin of view and description

Gadfly belongs to the family of diptera parasitic arthropod insects that are ecologically related to human settlements, that is, they are synanthropic flies. All of them lay their eggs in living flesh. At the moment, there are about 170 different types of gadflies, and some of them can harm human health and even cause their death. The oldest fossil remains of these flies were discovered in the United States in sediments over 50 million years old dating back to the Eocene era.

The most dangerous types of gadflies:

  • American cutaneous;
  • equine or gastric;
  • bovine subcutaneous gadfly;
  • cavity or nasopharyngeal sheep gadfly.

They all differ in the place of parasitism, the method of introducing their eggs into the body of a mammal, and the type of mouth opening. Each species prefers to use a certain animal to feed its offspring. The most dangerous for humans is the abdominal and gastric appearance.

An interesting fact: To infect these parasites, a person sometimes just needs to eat foods on the surface of which eggs of the gadfly have come to. Inside the body, the larvae begin to develop very actively, feeding on their prey, and the person loses vital energy. Migration of larvae through the body triggers pathological processes that can cause very serious health problems, human deaths are not uncommon.

Appearance and features

Photo: What a gadfly looks like

Despite the large number of types of gadflies, they all have common features in the structure of their bodies and a similar appearance:

  • their body length varies from 1.5 to 3 cm, depending on the species;
  • the oral apparatus is absent or reduced, and upon closer examination, church-shaped jaws can be seen on the head;
  • body with a large number of villi;
  • large eyes with multi-colored overflow;
  • body is roundish, wide enough;
  • the gadfly has 6 legs, the front legs are slightly shorter than the hind legs;
  • coarse-mesh wings are translucent, slightly longer than the body.

Depending on the species and habitat, the color of parasitic flies can be different. The southern latitudes are characterized by the presence of orange-black stripes on a particularly shaggy body. In the north, these insects have a calm, rather nondescript color: dark gray, brown, various shades of blue. Gadflies are often confused with horseflies, but if you carefully examine the appearance of these flies, the differences between these insects are quite significant, and the latter are blood-sucking.

An interesting fact: Gadfly is able to fly at a speed of up to 120 km per hour, which is comparable to the speed of movement of a dragonfly.

The worm-shaped larva of gadflies reaches a length of 2-3 cm. The body is dirty white in color divided into separate segments. She moves with the help of special outgrowths-hooks.

Where does the gadfly live?

Photo: Insect gadfly

These parasitic flies are widespread throughout the world, they live on almost all continents except for regions where it is very cold and keeps a constant minus. They are quite thermophilic and breed quickly in the southern latitudes — here you can find them in huge numbers. In Russia, some species are found even in the north of the country, the Urals, Siberia. Specimens that are especially dangerous for life and human health live only in hot, humid climates and they do not occur in our country.

Since for breeding they need the presence of large concentrations of mammals, they settle near livestock farms and pastures. A large number of adult gadflies can be observed near rivers, swamps, lakes. They love heat, sun and moisture. Quite often, gadgets scour the forests, fields and meadows, but they again return to their usual place of residence and remain there all their lives.

Interesting fact: Parasitizing on sheep, cows, gadflies cause great damage to livestock. If there are not enough objects in the field of view of an adult individual whose eggs can be laid in the body, then the whole huge portion of the larvae goes to one animal, which subsequently most often dies in torment. But even several cavitary or subcutaneous parasites can cause serious disturbances in the functioning of animal organs.

What does a gadfly eat?

Photo: Fly Gadfly

Adult individuals never feed, they do not even have a developed oral apparatus, and gadflies exist only due to pre-accumulated reserves, which, while still being a larva, “ate” inside the body of a mammal. During its short life, the adult gadfly loses about a third of its weight and dies due to severe exhaustion. In order to save energy and extend the period of their existence, in windy and cold weather, females try to move as little as possible, remaining in secluded places among the grass, in the bark of trees.

Larvae grow inside a mammal due to the nutrients found in the tissues of its body. They can migrate according to their host, choosing the most suitable and nutritious environment for themselves. Some species are found mainly in the intestinal tract and, ripening, go out with the feces of the animal, others do not go so deep, being close to the surface of the skin.

Sometimes the larvae reach the brain of their host, parasitize even in the eyeball, causing complete blindness. In the presence of parasites, the affected body rapidly loses nutrients, weight decreases, peculiar fistulas form on the surface of the skin, and the functioning of organs is disrupted.

Interesting fact: Cavity gadflies are viviparous insects, they give birth to their larvae and literally spray into the nostrils, the eyes of the future owner.

Now you know what happens when a gadfly bites. Let’s find out how an insect survives in the wild.

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Features of character and lifestyle

Photo: Gadfly in nature

Gadflies are characterized by the formation of so-called «male harems», when a huge number of males gather in the dry lowlands. Females during the mating season themselves fly to them, and then immediately go in search of a suitable animal for laying eggs. Depending on the type of parasite, the females behave differently during the attack: some make short flights and crawl imperceptibly to the victim, while others, on the contrary, circle over the herd, making a loud characteristic sound.

Gadfly is distinguished by its importunity, they do not leave the animal alone for a long time until they reach their goal. Cows feel the approach of these flies and often go in large groups, stopping drinking water and feeding. They behave very aggressively and if there is a large body of water nearby they tend to enter it through their nostrils, but even in this case the gadfly has a clearly developed tactic.

The beginning of the summer of gadflies, its duration directly depends on the zonal conditions of their development. It is much longer in the piedmont, mountainous regions, the middle lane and shorter in the southern regions, on the northern border of their habitat. Depending on the ambient temperature, wind and the presence of precipitation, flight dates can be shifted by 2-3 weeks.

Social structure and reproduction

Photo: Insect gadfly

The gadfly undergoes a complete transformation cycle: an egg, a larva, a chrysalis, and an adult — an adult. Life expectancy does not exceed one year, despite the fact that the imago exists from a week to one month, since it generally does not receive nutrition from the outside. After fertilization of the eggs, the female seeks to place them on the skin of the mammal as quickly as possible.

Some species of gadflies use mosquitoes to introduce their larvae into the body of the animal: for this, they attach eggs to the legs of these bloodsuckers and when the mosquito comes in contact with the surface of the victim’s body, the larvae hatch, penetrating through the puncture site. Hollow gadfly can place their eggs on plants, feed, which pets then eat.

Larvae continue their development in their intestines, and then go out together with litter in pupated form. Flies can also attach their eggs in the area of ​​the nostrils, livestock lips, so that when they lick the animals swallow them. A female at a time has up to 700 pieces of eggs, which she needs to quickly attach in a safe, warm place. Most often, the gadfly catches them to the hair of the animal, where larvae form inside the eggs under the influence of heat — only a fifth of the clutch survives.

Then the larvae pass through the epidermis and penetrate into the tissues:

  • at the initial stage, the body length of the larva is 1.5-2.5 mm, but it actively feeds on the host blood and increases several times over a short period;
  • at the second stage of its development, a grown and stronger larva tends closer to the surface of the skin and releases two spiracles for oxygen. Large fistulas form on the body of animals at this time;
  • a protective capsule from connective tissues begins to form in the fistula, here the larva matures to the stage of the pupa and then gets out;
  • the process of transforming a pupa into an imago takes from 20 to 40 days.

There are many ways for these parasites to enter the body of a mammal. The process of exit of adults from pupae takes only a few seconds and almost immediately a fly is born that is able to fly, mate.

Natural enemies of gadflies

Photo: Fly Gadfly

Gadfly has very few natural enemies in nature for the reason that an adult lives very little and prefers to hide in secluded, dark places. If females make flights, then males sometimes do not rise at all from the surface of the grass. Hunting for gadflies, while both adults and their larvae, can be mainly only birds, sometimes ladybugs and praying mantises join them. Often these insects are used as a biological weapon against gadflies.

In connection with the enormous damage that these insects inflict on animal husbandry, a constant struggle is being waged against gadflies. Various chemical compositions are used to spray their habitats, cattle skin is treated as a preventive measure — with timely treatment, animals can be protected from the penetration of larvae into the body. It has been observed that during the active summer of these parasite flies, livestock gain is reduced by a third, and milk yield by 15 percent.

An interesting fact: Gadfly prefer to live among dense vegetation, where they can hide, so sometimes it’s enough to remove bushes and cut grass to make them disappear from a certain plot of land.

A dangerous human gadfly cannot survive in our weather conditions, but in the conditions of Central and South America it feels very comfortable.

Population and species status

Photo: What a gadfly looks like

The amazing fecundity, adaptability of gadflies and the small number of natural enemies allows them to multiply to huge numbers, thereby causing large losses to livestock farms. Despite the actively applied measures on the part of humans against the propagation of gadflies, their population is rapidly recovering in a short period of time. The status of the species is stable and it is practically not affected even by changes in the ecological situation in its environment.

Adult gadflies never drink blood, but sometimes they can annoy at times more than ordinary horseflies and cause serious health problems, even death. For this reason, people also need to protect themselves from their attacks when they are outdoors with repellents, and observe a number of safety rules.

Interesting fact: If the gadfly larvae are detected in humans in time, then they are removed exclusively by surgery and the likelihood of infection of the body is virtually eliminated. If the larva is detected too late, then with a high degree of probability it will not be possible to avoid complications — sepsis develops. Another complication of the activity of the larvae inside the human body can be an allergic reaction of the body: from ordinary urticaria to a deadly anaphylactic shock.

Gadfly It’s not just an annoying large fly that you can meet while fishing, in a park or in a summer house — it’s a very dangerous parasitic insect whose offspring can cause significant harm to both livestock and humans, but, nevertheless, the gadfly is very peculiar a creature quite interesting to study.

Nasopharyngeal Cancer

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Nasopharyngeal cancer is a rare type of head and neck cancer. It starts in the upper part of your throat, behind the nose. This area is called the nasopharynx.

The nasopharynx is precariously placed at the base of your skull, above the roof of your mouth. Your nostrils open into the nasopharynx. When you breathe, air flows through your nose into your throat and nasopharynx, and eventually into your lungs.

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Nasopharyngeal cancer is also called nasopharyngeal carcinoma (NPC).

Causes of Nasopharyngeal Cancer

Scientists are not sure what exactly causes nasopharyngeal cancer. However, the cancer has been strongly linked to the Epstein-Barr virus (EBV).

Although EBV infection is common, not everyone who has EBV will get nasopharyngeal cancer. In the U.S., most people who have had an EBV infection never have long-term problems. Scientists are still researching how EBV leads to nasopharyngeal cancer, but it may be related to genetic material (DNA) from the virus affecting the DNA in the cells of the nasopharynx. The change in DNA causes cells to grow and divide abnormally, causing cancer.

The risk for NPC goes up if you eat a diet rich in salt-cured fish and meat. Tobacco and alcohol may also increase the risk, although their link to NPC is not clear. Some scientists believe that chemicals in these things further damage the DNA in cells.

Who Gets Nasopharyngeal Cancer?

Fewer than one in every 100,000 people in the U.S. gets this type of cancer, according to the American Cancer Society.

The cancer is most common in southern China and southeast Asia. It is also much more common in:

  • Other parts of Asia
  • North Africa
  • Inuit populations of Alaska and Canada
  • Chinese and Hmong immigrant groups in the U.S.

In the U.S., nasopharyngeal cancer has also been seen in African-Americans, Hispanics, and white people.

You are more likely to get this type of cancer if you:

  • Are male
  • Eat a diet rich in salt-cured fish and meats
  • Have a family history of nasopharyngeal cancer
  • Have certain genes linked to cancer development
  • Have come in contact with EBV

Some, but not all, studies have found a higher risk of nasopharyngeal cancer in people who:

  • Smoke
  • Drink a lot of alcohol
  • Work around wood dust or a chemical called formaldehyde


Nasopharyngeal Cancer Symptoms

Symptoms of nasopharyngeal cancer may include:

  • Lump in neck (most common)
  • Blurry or double vision
  • Ear infections that recur
  • Face pain or numbness
  • Headache
  • Hearing loss, ringing in the ears, or a feeling of fullness in the ear
  • Difficulty opening mouth
  • Nosebleeds
  • Stuffy nose
  • Sore throat

Keep in mind, such symptoms are more likely to occur with many other diseases and health conditions that are far less serious than nasopharyngeal cancer.

If you have any of the above symptoms, see your doctor or nurse. Only an experienced medical person can diagnose or rule out nasopharyngeal cancer.

How Nasopharyngeal Cancer Is Diagnosed

Your doctor or nurse will ask you questions about your symptoms, medical history, and family history, and perform a physical exam. This includes a detailed look at your ears, nose, and throat. You may be sent to a doctor who specializes in these areas, called an otolaryngologist.

The doctor or nurse will also feel your neck. Most patients with nasopharyngeal cancer have a lump in the neck. This is a sign that the cancer is spreading to the lymph nodes.

A flexible, lighted tube may be placed through your mouth or nose to help the doctor better view the nasopharynx. This is called a nasopharyngoscopy. It helps the doctor check the area for abnormal growths, bleeding, or other problems.

If the exam is abnormal, your doctor may recommend a biopsy. A biopsy is the removal of a small amount of tissue for examination under a microscope.

A biopsy may be taken during the nasopharyngoscopy. If there is a lump in your neck, the biopsy may be done by placing a very thin, hollow needle into the lump.

Imaging tests can help spot nasopharyngeal cancer or determine if it has spread. Imaging tests may include:

The following tests may also be performed:

If you are diagnosed with nasopharyngeal cancer, other tests will be done to determine if and where the cancer has spread. This is called staging.

Nasopharyngeal cancer is staged from Stage 0 (the earliest stage) to Stage IV (the most advanced stage). The lower the number, the less the cancer has spread to other parts of the body.

  • Stage 0 is called carcinoma in situ.
  • Stage I is early-stage nasopharyngeal cancer that has not spread to lymph nodes or distant parts of the body.
  • Stage II is nasopharyngeal cancer that may have spread to nearby tissues and lymph nodes but has not spread to distant parts of the body.
  • Stages III and IV are considered more advanced because of tumor size, extent of spread to nearby tissues, lymph nodes, and/or distant parts of the body.
  • If nasopharyngeal cancer returns, it is called recurrent cancer.


Nasopharyngeal Cancer Treatment

If you are diagnosed with nasopharyngeal cancer, you will need regular follow-ups with your medical team before, during, and after treatment.

Your treatment will depend on many things, including:

  • Location of the tumor
  • Stage of the tumor
  • Your overall health

Treatment may include:

Radiation Therapy . Radiation therapy uses X-rays to kill cancer cells and stop them from growing. It is usually part of the standard treatment for early stage nasopharyngeal cancer.

One type called IMRT delivers high-dose radiation directly to the tumor while minimizing damage to nearby healthy tissue. It may cause fewer side effects or complications than conventional radiation treatment to the nasopharynx, which can lead to:

  • dry mouth
  • inflammation of the lining of your mouth and throat
  • blindness
  • brain stem injury
  • death of healthy tissue
  • tooth decay

Chemotherapy. Chemotherapy uses drugs to kill cancer cells. By itself, it is not usually helpful for treating nasopharyngeal cancer. But it may help you live longer when combined with radiotherapy or biological drugs.

Surgery. Surgery to remove the tumor is not often performed because of the tumor’s location near nerves and blood vessels. It may cause permanent damage to the eye and other nearby structures.

Not all people with nasopharyngeal cancer can have surgery. Your doctor will consider the location and stage of your tumor when discussing your treatment options.

Biologic drugs. Biologic drugs affect how your body’s immune system fights disease. They include monoclonal antibodies such as cetuximab (Erbitux), pembrolizumab (Keytruda), and nivolumab (Opdivo). Biologics work differently than chemotherapy drugs and may be used more often in cases of advanced or recurrent cancer.

Palliative therapy. The goal of palliative treatment is to control symptoms related to cancer and cancer treatment and make you as comfortable as possible.

Clinical trials . If treatment does not work, consider joining a clinical trial. Researchers are always testing new ways to treat cancer, and they need your help. Ask your doctor or nurse if there are any clinical trials on nasopharyngeal cancer in your area.

Can Nasopharyngeal Cancer Be Prevented?

Many cases of nasopharygeal cancer are not preventable, but taking these steps may help lower your risk of nasopharyngeal cancer:

  • Avoid salt-cured fish and meats.
  • Do not smoke.
  • Do not drink a lot of alcohol.


American Cancer Society web site: «Nasopharyngeal Cancer.»

National Cancer Institute web site: «Nasopharyngeal Cancer.»

Cummings, C.W., Flint, P.W., Haughey, B.H., editors. Otolaryngology: Head & Neck Surgery. 5th ed., Mosby Elsevier, 2010.

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Carey, W.D., editor, Cleveland Clinic: Current Clinical Medicine 2010, 2nd ed., Saunders Elsevier, 2010.

American Society of Clinical Oncology: «Nasopharyngeal Cancer.»

Abeloff, M.D., Armitage, J.O., Niederhuber, J.E., Kastan, M.B., McKenna, W.G., editors, Abeloff’s Clinical Oncology, 4th ed., Elsevier Churchill Livingstone, 2008.

Hui, E.P., Chan, A.T.C., Le, Q-T. «Treatment of early and locoregionally advanced nasopharyngeal carcinoma,» UpToDate version 19.2; September 2011, last updated Nov. 14, 2011.

Colin S Poon, MD, PhD, FRCPC, Kerstin M Stenson, MD, «Overview of the diagnosis and staging of head and neck cancer,» 2019

Edwin P Hui, MD, Anthony TC Chan, MD, «Epidemiology, etiology, and diagnosis of nasopharyngeal carcinoma,» 2019


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Definition of parasite

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Synonyms for parasite


  • bloodsucker,
  • free rider,
  • freeloader,
  • hanger-on,
  • leech,
  • moocher,
  • sponge,
  • sponger

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Choose the Right Synonym for parasite

parasite, sycophant, toady, leech, sponge mean a usually obsequious flatterer or self-seeker. parasite applies to one who clings to a person of wealth, power, or influence or is useless to society. a jet-setter with an entourage of parasites sycophant adds to this a strong suggestion of fawning, flattery, or adulation. a powerful prince surrounded by sycophants toady emphasizes the servility and snobbery of the self-seeker. cultivated leaders of society and became their toady leech stresses persistence in clinging to or bleeding another for one’s own advantage. a leech living off his family and friends sponge stresses the parasitic laziness, dependence, and opportunism of the cadger. a shiftless sponge, always looking for a handout

Examples of parasite in a Sentence

These example sentences are selected automatically from various online news sources to reflect current usage of the word ‘parasite.’ Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

First Known Use of parasite

1539, in the meaning defined at sense 1

History and Etymology for parasite

Middle French, from Latin parasitus, from Greek parasitos, from para- + sitos grain, food

Parasitism: Definition and Examples

What Are Parasites and Why Do We Need Them?

  • Ph.D., Biomedical Sciences, University of Tennessee at Knoxville
  • B.A., Physics and Mathematics, Hastings College

Parasitism is defined as a relationship between two species in which one organism (parasite) lives on or within the other organism (host), causing the host some degree of harm. A parasite reduces its host’s fitness but increases its own fitness, usually by gaining food and shelter.

Key Takeaways: Parasitism

  • Parasitism is a type of symbiotic relationship in which one organism benefits at the expense of another.
  • The species that benefits is called the parasite, while the one that is harmed is called the host.
  • Over half of all known species are parasites. Parasites are found in all biological kingdoms.
  • Examples of human parasites include roundworms, leeches, ticks, lice, and mites.

The term «parasite» comes from the Greek word parasitos, which means «one who eats at the table of another.» The study of parasites and parasitism is called parasitology.

There are parasites belonging to every biological kingdom (animals, plants, fungi, protozoa, bacteria, viruses). In the animal kingdom, every parasite has a free-living counterpart. Examples of parasites include mosquitoes, mistletoe, roundworms, all viruses, ticks, and the protozoan that causes malaria.

Parasitism vs. Predation

Both parasites and predators rely on another organism for one or more resources, but they have numerous differences. Predators kill their prey in order to consume it. As a result, predators tend to be physically larger and/or stronger than their prey. Parasites, on the other hand, tend to be much smaller than their host and do not normally kill the host. Instead, a parasite lives on or within the host for a period of time. Parasites also tend to reproduce much more quickly than hosts, which is not usually the case in predator-prey relationships.

Parasitism vs. Mutualism vs. Commensalism

Parasitism, mutualism, and commensalism are three types of symbiotic relationships between organisms. In parasitism, one species benefits at the expense of the other. In mutualism, both species benefit from the interaction. In commensalism, one species benefits, while the other is neither harmed nor helped.

Types of Parasitism

There are multiple ways to classify types of parasitism.

Parasites may be grouped according to where they live. Ectoparasites, such as fleas and ticks, live on the surface of a host. Endoparasites, such as intestinal worms and protozoa in blood, live inside a host’s body. Mesoparasites, such as some copepods, enter the opening of a host body and partially embed themselves.

The life cycle can be a basis for classifying parasites. An obligate parasite requires a host in order to complete its life cycle. A facultative parasite can complete its life cycle without a host. Sometimes location and life cycle requirements may be combined. For example, there are obligate intracellular parasites and facultative intestinal parasites.

Parasites may be classified according to their strategy. There are six major parasite strategies. Three relate to parasite transmission:

  • Directly transmitted parasites, such as fleas and mites, reach their host on their own.
  • Trophically transmitted parasites, such as trematodes and roundworms, are eaten by their host.
  • Vector transmitted parasites rely on an intermediate host to transport them to their definitive host. An example of a vector transmitted parasite is the protozoan that causes sleeping sickness (Trypanosoma), which is transported by biting insects.

The other three strategies involve the parasite’s effect on its host:

  • Parasitic castrators either partly or fully inhibit a host’s reproductive ability but allow the organism to live. The energy the host would have put toward reproduction is diverted toward supporting the parasite. An example is the barnacle Sacculina, which degenerates the gonads of crabs such that males develop the appearance of females.
  • Parasitoidseventually kill their hosts, making them nearly predators. All examples of parasitoids are insects that lay their eggs on or inside the host. When the egg hatches, the developing juvenile serves as food and shelter.
  • A micropredator attacks more than one host so that most host organisms survive. Examples of micropredators include vampire bats, lampreys, fleas, leeches, and ticks.

Other types of parasitism include brood parasitism, where a host raises the young of the parasite (e.g., cuckoos); kleptoparasitism, in which a parasite steals the host’s food (e.g., skuas stealing food from other birds); and sexual parasitism, in which males rely on females for survival (e.g., anglerfish).

Why We Need Parasites

Parasites harm their hosts, so it’s tempting to think they should be eradicated. Yet, at least half of all known species are parasitic. Parasites serve an important role in an ecosystem. They help control dominant species, allowing for competition and diversity. Parasites transfer genetic material between species, serving a role in evolution. In general, the presence of parasites is a positive indication of ecosystem health.

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