The gadfly is a large parasitic fly, about which you can hear many incredible stories, in particular about their terrible bites and larvae, which are not deposited in the body of the victim. There are many misconceptions about the habits and lifestyle of these insects, and the main one is that these large flies suck blood. In fact, adults are not blood-sucking – they do not feed at all during the entire period of their existence, but nevertheless they can cause much more harm.

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Photo: Gadfly

Photo: Gadfly

Gadflies belong to the family of diptera parasitic arthropod insects, which are ecologically associated with human settlements, that is, they are synanthropic flies. They all 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 death. The oldest fossils of these flies were found in the United States in sediments over 50 million years old dating back to the Eocene epoch.

Video: Gadfly

The most dangerous types of gadflies:

  • American dermal;
  • horse or stomach;
  • bovine subcutaneous gadfly;
  • cavitary or nasopharyngeal sheep gadfly.

They all differ in the place of parasitism, the way their eggs are introduced 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 cavitary and gastric species are considered the most dangerous for humans.

An interesting fact: To become infected with these parasites, it is sometimes enough for a person to only eat foods on the surface of which gadfly eggs have fallen. Inside the body, the larvae begin to develop very actively, feeding on their prey, and the person is deprived of vital energy. The migration of larvae throughout the body triggers pathological processes that can cause very serious health problems, and death of a person is not uncommon.

Appearance and features

Photo: What a gadfly looks like

Photo: What a gadfly looks like

Despite the large the number of species 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 mouth apparatus is absent or reduced, and upon closer examination, church-shaped jaws can be seen on the head;
  • the body with a large number of villi;
  • large eyes with a multi-colored overflow;
  • the body is rounded, fairly wide;
  • the gadfly has 6 legs, the front legs are somewhat shorter than the hind ones;
  • the wings with a large mesh are translucent, slightly longer than the body.


Depending on the species and habitat, the color of parasitic flies can be different. For southern latitudes, the presence of orange-black stripes on a particularly furry body is characteristic. In the north, these insects have a calm, rather nondescript color: dark gray, brown, various shades of blue. Very often, gadflies are confused with horseflies, but if you carefully study the appearance of these flies, then the differences between these insects are quite significant, besides, the latter are bloodsucking.

An interesting fact: Gadflies are capable of flying at speeds up to 120 km per hour, which is comparable to the speed of a dragonfly.

A worm-like larva of gadflies reaches a length of 2-3 cm. The body is dirty white colors are divided into separate segments. She moves with the help of special growths-hooks.

Where does the gadfly live?

Photo: Gadfly Insect

Photo: Gadfly Insect

These parasitic flies are widespread throughout the world, they live on almost all continents except for regions where it is very cold and there is a constant minus. They are quite thermophilic and multiply rapidly precisely in the southern latitudes – here they can be found in huge quantities. In Russia, some species are found even in the north of the country, the Urals, and Siberia. Particularly dangerous to life and human health, specimens live only in a hot, humid climate and they are not found in our country.

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

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

What does the gadfly eat?

Photo: Gadfly fly

Photo: Gadfly fly

Adult individuals never feed, they do not even have a developed mouth apparatus, and gadflies exist only at the expense of pre-accumulated reserves, which, while still being a larva, “ate” inside the mammal’s body. During its short life, an 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.

The larvae grow inside the mammal due to the nutrients found in the tissues of its body. They can migrate through their host, choosing the most suitable and nutritious environment for themselves. Some species are found predominantly in the intestinal tract and, when mature, exit with the animal’s feces, others do not go as 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 organism rapidly loses nutrients, weight decreases, peculiar fistulas form on the surface of the skin, and the functioning of organs is disrupted.

Interesting fact: Gadflies are viviparous insects; and literally sprayed into the nostrils, the eyes of the future owner.

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

Character and lifestyle features

Photo: Gadfly in nature

Photo: Gadfly in nature

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

Gadflies are distinguished by their 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 huddle in large groups, ceasing to drink water and feed. They behave very aggressively and, if there is a large reservoir nearby, they tend to go into it up to their very nostrils, but in this case, the gadflies have a well-developed tactic.

The beginning of the flight of gadflies, its duration directly depends on the zonal conditions of their development. It is much longer in the foothills, 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 precipitation, the flight dates can be shifted by 2-3 weeks.

Social structure and reproduction

Photo: Gadfly Insect

Photo: Gadfly Insect

The gadfly goes through a full cycle of transformation: egg, larva, pupa, imago – an adult. Life expectancy does not exceed one year, despite the fact that the imago exists from a week to one month, since it does not receive food from the outside at all. After fertilization of the eggs, the female seeks to place them on the skin of a mammal as quickly as possible.

Some species of gadflies use mosquitoes to introduce their larvae into the animal’s body: to do this, they attach eggs to the legs of these bloodsucking and upon contact of the mosquito with the surface the bodies of the prey larvae hatch, penetrating through the puncture site inside. Cavernous gadflies can place their eggs on plants, feed, which pets then eat.

The larvae continue their development in their intestines, and then come out with the litter in a pupated form. Flies can also attach their eggs in the region of the nostrils, lips of livestock, so that when licked, the animals swallow them. The female has up to 700 eggs at a time, which she needs to quickly attach to a safe, warm place. Most often, the gadfly clings to the fur of the animal, where larvae are formed inside the eggs under the influence of heat — only a fifth of the clutch survives.

Then the larvae pass through the epidermis and invade the tissues:

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

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

Natural enemies of gadflies

Photo: Gadfly fly

Photo: Gadfly fly

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

Due to the enormous damage that these insects cause to livestock, there is a constant struggle against gadflies. Various chemical compositions are used to spray their habitual habitats, cattle skin is processed for preventive purposes – with timely processing, animals can be protected from the penetration of larvae into the body. It has been observed that during the active summer of these parasitic flies, livestock gain is reduced by a third, and milk yield by 15 percent.

Interesting fact: Gadflies prefer to live among dense vegetation, where they can hide , therefore, sometimes it is enough to remove thickets of bushes and mow the grass so that they disappear from a certain piece of land.

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

Population and species status

Photo: What a gadfly looks like

Photo: What a gadfly looks like

The amazing fecundity, adaptability of gadflies and a small number of natural enemies allows them to multiply to huge numbers, thereby causing great losses to livestock farms. Despite the actively applied human measures against the reproduction of gadflies, their population is quickly restored in a short period of time. The status of the species is stable and is practically not affected even by changes in the ecological situation in its habitat.

Adult gadflies never drink blood, but sometimes they can annoy many 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 in nature with the help of repellents, follow a number of safety rules.

Interesting fact: If gadfly larvae are found in time in humans, then they are removed exclusively surgically and the likelihood of infection of the body is practically excluded. 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 larvae inside the human body can be an allergic reaction of the body: from ordinary urticaria to deadly anaphylactic shock.

The gadfly is not just an annoying large fly that you can meet on fishing, in the park or cottage — this is a very dangerous parasitic insect, the offspring of which can cause significant harm to both livestock and humans, but, nevertheless, the gadfly — a very peculiar creature, quite interesting to study.

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