Why do flies bug us so much? The CSIRO helps dispel urban myths
- From: News Corp Australia Network
- October 18, 2013
IT'S that time of year - the flies are out in force in Australia and they are very annoying.
There are around 20,000 different species of flies in this country, and at times it can feel like they all want to land on you at once.
But in reality, there is only one species that is attracted to us humans - and it's the Bush Fly, scientifically known as Musca vetutissima. Its cousin the House Fly, Musca domestica, is attracted less to us and more to things in our homes.
They are brought back by the seasonal cycle and have given us the "Aussie salute" - the flappy wave meant to keep them out of one's face.
But why are they attracted to humans so much? Why do they persist in trying to land on us?
CSIRO Senior Principal Research Scientist and Director of the Australian National Insect Collection Dr David Yeates said these flies are attracted to certain secretions on the skin which they can feed on, survive and help mature their eggs before they are laid.
"The Bush Fly has a very soft, fleshy mouth with parts that are like a sponge and when it lands on you and touches your skin, it won't bite, it will suck up secretions on the skin," he said.
"There's sweat, proteins, carbohydrates, salts, sugars and other chemicals flies are interested in feeding on.
"There are also dead pieces of skin coming off all the time which they can make a living on."
Dr Yeates said this type of fly also likes to get its nutrients from sitting around the eyes of livestock.
"It is hard to get it from anywhere else on hairy animals, which is also why they land more often on our skin."
But what about the urban myths around these flies? Here's some below:
Do they bite you?
No, Bush Flies/House Flies don't bite.
Do they suck your blood?
No. Dr Yeates said: "There are other flies that feed on blood like mosquitos, sandflies and blackflies. Stable flies that hang around horse and livestock stables also bite."
Are they attracted to fragrant scents?
No. Your perfume, aftershave or hair shampoo will not have any impact on how many flies try to land on you.
Do they poo on us?
They might. "They are not toilet-trained, but it's not noticeable," he said.
Do they vomit on you?
No. But Dr Yeates said: "One of the way these flies feed, when they land on a table and there's a grain of sugar, they don't have mouths to chew it up. So they walk up to it and regurgitate or spew on to it, turn it into a liquid they can suck up."
Some say they carry millions of germs, do they spread them?
No. They do not carry millions of germs. Dr Yeates said: "It's possible for them to carry some germs given what they do in their lifestyle, but in general, Bush Flies are not a giant health risk.
"If a fly has laid eggs on poo and comes to you, then whatever was on its feet could come to you too. It could be bad if they sit on an open wound, as it could lead to an infection.
"And Bush Flies transmit a bacteria that causes trachoma in some parts of Western Australia and the Northern Territory."
Do they lay eggs on our skin?
No. Dr Yeates said: "These flies go and lay eggs in sheep, horse, dog or cow poo. In very hot conditions, it will take a few days for them to hatch. Their life cycle is about 10 days to 2 weeks in summer. Depending on the size of the female, they lay about 100-200 eggs."
Finally, do we even need flies?
Yes. Flies have a large role in the recycling of nutrients from organic matter, which can be absorbed by plants.
Dr Yeates said: "The are nature's great recyclers. They are really important. If we didn't have them organic matter not able to be absorbed by plants. Flies are also important in pollination of native plants and crops, and predatory and parasitic flies also help to regulate the populations of other insects. In compost (for example), flies are doing most of the work. They eat scraps and then excrete and turn it into a substance plants can use when you put it back in the garden."