Flies - A Blessing And A Curse
Flies belong to the order Diptera, and are classified as insects with a single pair of wings. The order contains an astonishing 240,000 estimated species, including gnats, midges and mosquitoes. It doesn't include other insects known as flies, such as dragonflies, as these have more than one pair of wings and belong to a different order. Only 'true flies' have a single pair of wings.
Flies have evolved to be great fliers, and have short and streamlined bodies for the purpose. The part of their bodies that contains the flight muscles is greatly enlarged, while the rest is much reduced. The third segment of a fly's body (or thorax) contains structures known as halteres. These were originally a second set of wings, but have adapted over time to help stabilise flight.
The most common of all domestic flies is the housefly. They're easily recognised by their grey thorax, four dark lines on their back, large red compound eyes and short hairs covering their bodies. Adults are generally 8 to 12 mm long, the females tending to be larger than the males.
Houseflies only consume liquid food. They feed on faeces, sputum and decaying organic matter such as food and flesh. To eat, flies predigest food by spitting saliva on to it, then sucking it up using their specialised mouthparts. A fly can also regurgitate partially digested food and pass it back into the abdomen.
Because of their high food intake, houseflies expel faeces almost constantly, which makes them a significant carrier of pathogens. They can also carry organisms on their body hair and mouths. Houseflies are known to contribute to the spread of cholera, typhoid, dysentery and also viruses, and as they can fly up to a mile at a time, it's little wonder they're such a key vector of infectious diseases.
Flies in general are important transmitters of disease. Mosquitoes in particular carry a huge number of serious illnesses, with malaria being perhaps the most well-known. However, they also contribute to the spread of dengue fever, yellow fever, the West Nile virus and encephalitis. Small wonder mosquitoes are not highly regarded, especially in the developing world where these illnesses cause a large number of deaths every year.
On top of this, flies have even played their part in Greek mythology. Zeus sent a fly to bite Pegasus, causing him to throw the hero Bellerophon from his back and preventing him from reaching Mount Olympus, home of the gods. And of course flies are a useful symbol in horror films, signifying death, or even creating the horror themselves in movies like 'The Fly'. So flies are considered a nuisance and parasite, but they have occasionally brought something positive to the world.
Flies have evolved to be great fliers, and have short and streamlined bodies for the purpose. The part of their bodies that contains the flight muscles is greatly enlarged, while the rest is much reduced. The third segment of a fly's body (or thorax) contains structures known as halteres. These were originally a second set of wings, but have adapted over time to help stabilise flight.
The most common of all domestic flies is the housefly. They're easily recognised by their grey thorax, four dark lines on their back, large red compound eyes and short hairs covering their bodies. Adults are generally 8 to 12 mm long, the females tending to be larger than the males.
Houseflies only consume liquid food. They feed on faeces, sputum and decaying organic matter such as food and flesh. To eat, flies predigest food by spitting saliva on to it, then sucking it up using their specialised mouthparts. A fly can also regurgitate partially digested food and pass it back into the abdomen.
Because of their high food intake, houseflies expel faeces almost constantly, which makes them a significant carrier of pathogens. They can also carry organisms on their body hair and mouths. Houseflies are known to contribute to the spread of cholera, typhoid, dysentery and also viruses, and as they can fly up to a mile at a time, it's little wonder they're such a key vector of infectious diseases.
Flies in general are important transmitters of disease. Mosquitoes in particular carry a huge number of serious illnesses, with malaria being perhaps the most well-known. However, they also contribute to the spread of dengue fever, yellow fever, the West Nile virus and encephalitis. Small wonder mosquitoes are not highly regarded, especially in the developing world where these illnesses cause a large number of deaths every year.
On top of this, flies have even played their part in Greek mythology. Zeus sent a fly to bite Pegasus, causing him to throw the hero Bellerophon from his back and preventing him from reaching Mount Olympus, home of the gods. And of course flies are a useful symbol in horror films, signifying death, or even creating the horror themselves in movies like 'The Fly'. So flies are considered a nuisance and parasite, but they have occasionally brought something positive to the world.
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