Some flies are very big.
They like to fly in the sun. The moms bite to get food. This helps them make eggs. They live all over the world.
Have you seen a big fly?
Some flies are very big.
These flies like to fly in the sun. They do not like the dark.
The mom flies bite animals. They do this to get food. This food helps them make eggs.
They have big eyes. The eyes have many parts.
These flies live all over the world. They are not in the cold polar lands.
Horse flies and deer flies belong to a group called Tabanidae.
These flies are found all over the world. They do not live in very cold places like Greenland or Iceland. Most like to fly in the bright sun. They stay still at night.
Adult males and females eat nectar from plants. This helps them get power. But female flies need more food to make eggs. They bite animals to get blood.
Their mouths are very strong. They have sharp blades to cut skin. They also have a part like a sponge. This part laps up the blood.
These flies have large compound eyes. These eyes are made of many tiny parts. The eyes help them see colors and motion. Some flies have very long mouths for sipping nectar.
Female flies can pass germs from one animal to another. This happens when they bite. They can also make cows less healthy. This can lower how much milk a cow makes.
Horse flies and deer flies are part of a large family called Tabanidae.
These insects are found all over the world. They live in many places, from deserts to high mountains. However, they do not live in very cold areas like Greenland, Iceland, or Hawaii. Most of these flies like to fly in the bright sunlight. They stay inactive during the night.
Adult flies use different ways to find food. Both males and females eat nectar from flowers. Some species even help move pollen between plants. But female flies have a special need for protein to make eggs. They get this by biting land animals, including humans.
To do this, their mouths work like a tiny tool. They have two pairs of sharp cutting blades. These blades puncture the skin of an animal. Then, a sponge-like part laps up the blood that flows from the wound.
People have written about these flies for a very long time. In ancient Greece, the writer Aeschylus described a gadfly in a play. He wrote about a fly that chased a person named Io. Later, the philosopher Socrates used the gadfly as a symbol. He used it to describe how he asked many questions.
In 1665, Robert Hooke drew a very detailed picture of a drone fly. This was one of the first accurate drawings of these insects.
There are about 4,455 different species of Tabanidae. Many have different names depending on where they live. The genus *Tabanus* was first named by Pliny the Younger. The genus *Chrysops* was named by Johann Wilhelm Meigen in 1802.
Deer flies are often called *Chrysops* because they live near deer. Some people call them buffalo-flies or moose-flies. Other names like "stouts" come from their wide bodies. Some names like "cleg" come from the Old Norse language.
These flies have very interesting bodies and eyes. They have large compound eyes made of many tiny parts. These parts help them see motion and colors like blue and green.
Interestingly, they cannot see infrared light. This means they cannot detect heat from a distance. Their eyes are very important for finding where to land. Females have eyes that are far apart on their heads. In males, the eyes are almost touching.
Tabanidae is a large family of true flies within the insect order Diptera.
This family includes well-known insects like horse flies and deer flies. They are found across the entire globe. They live in diverse habitats ranging from dry deserts to alpine meadows. However, they are absent from certain islands like Hawaii, Greenland, and Iceland. They generally prefer warm environments and bright sunlight. They remain inactive during the night and avoid dark or shady areas.
Adult tabanids have very distinct physical features. They possess wide bodies and short antennae with three segments. Their large compound eyes are a primary feature. In female flies, these eyes are widely separated on the head. In males, the eyes are positioned so they are almost touching.
The eyes are often brightly colored in living insects. These eyes are made of many tiny optical units called ommatidia. Each unit contains a cluster of eight photoreceptor cells known as retinula cells. The outer cells detect motion and achromatic vision. The inner cells, called R7 and R8, detect color and light polarity.
Understanding how these flies see helps explain how they find food. The R7 and R8 cells are sensitive to specific wavelengths. R7 peaks in ultraviolet light. R8 peaks in blue or green light depending on the type of ommatidia. Because of this, tabanids cannot see infrared light. They cannot detect the heat of an animal from a distance. This disproves a common belief about their hunting methods. Instead, they rely on color and light polarization to target hosts.
Feeding habits vary between the sexes of the species. Both males and females consume nectar and plant exudates. Some species even act as pollinators for specialized flowers. Females have a different requirement because they need protein to produce eggs. To get this, they parasitize land vertebrates, including humans. The female mouthparts act as a stout stabbing organ. They use two pairs of sharp cutting blades to puncture skin. A spongelike part then laps up the resulting blood flow.
Different genera within the family show various specializations. The genus *Tabanus* contains the larger, stouter horse flies. These are often dark brown or black with metallic eyes. The genus *Chrysops* contains the deer flies. These are smaller and have striped abdomens and banded wings.
Some species in the subfamily Pangoniinae have an exceptionally long proboscis. This is a tubular mouthpart used for feeding. There are also yellow flies in the genus *Diachlorus*. These have yellowish bodies and purplish-black eyes with a green sheen.
Tabanids have a long history in human culture and science. The writer Aeschylus depicted a gadfly in his play *Prometheus Bound*. He described a fly driving the character Io to madness. Later, the philosopher Socrates used the gadfly as an ironic mascot. He compared his own persistent questioning to the fly. In 1665, Robert Hooke provided one of the first accurate depictions of a drone fly. He published this detailed drawing in his work *Micrographia*.
These insects play a significant role in many ecosystems and industries. There are approximately 4,455 described species of Tabanidae worldwide. Because females bite animals to feed, they can transfer blood-borne diseases. They have been known to carry the equine infectious anaemia virus and anthrax. They can also carry the filarial worm *Loa loa* and tularemia. In farming, they can reduce growth rates in cattle. They may also lower the milk output of cows if shelter is unavailable. This makes them a notable concern for livestock management.
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