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What Are House Flies?
House flies (Muscidae) are a small yet prominent species of nuisance fly found inside and outside our homes. The flies share a very close relationship with humans and human waste.
The size of house flies varies between just a 1-2mm. The common house fly is 7-8mm while the little house fly is 6-7mm in length.
Compound eyes appear red with the males and the larger females being distinguished by the width of the space between their eyes.
This fly species has only one pair of wings so falls neatly into the fly family of Diptera.
House Flies – Common Vs Lesser
Fortunately, telling the two apart is easy. The common housefly has four longitudinal dark lines on the thorax while the lesser house fly has three dark lines.
The common housefly is the fly more likely to be found inside while the lesser house fly prefers outdoor spaces.
Both variants of fly present as a persistent spring and summer nuisance and both flies are considered medically important to humans as vectors (carriers) of disease.
House Flies – Life-Cycle
Adult flies mate within 48 hours of hatching and females begin laying the first of several batches of 75-150 eggs within hours of mating.
Housefly (maggots) larvae hatch within a few days and take a few weeks to mature, pupate and hatch.
The literature on these flies is quite varied on the exact length of the lifecycle. In ideal conditions, the entire lifecycle is said to complete in just 7 days, but more usually in 14-28 days.
How Long Do House Flies Live?
Adult houseflies have a lifespan of 2-4 weeks. Life spans vary considerably on climate and food availability. Outside of the laboratory or controlled environments, the flies live between 7-14 days.
How Far Can House Flies Travel
The flies are easily carried from one location to the next assisted by prevailing winds. In calm conditions these flies will travel 1-2km at best. If conditions are good then travel over 7-10km is well documented.
Wind speed, wind direction, fly population densities, temperature and food availability all play a part in a flies need to extend its range beyond the immediate location.
Where Do House Flies Rest?
These flies have become notorious for flying around at head height, before landing on the exposed edges of lampshades, walls, and picture frames.
The house flies perching behaviour is what makes “sticky flypaper” so compelling.
This behaviour also provides reliable opportunities to apply residual pesticides or repellents to these surfaces, reducing a flies propensity to remain in vulnerable locations like kitchens and clinics.
Do House Flies Bite?
These flies do not have the machinery to bite, but they are closely related to the stable fly (Stomoxys calcitrans – “sharp-mouth – kicking”) which does bite!
Stable flies are exo-parasites, meaning they feed on the exterior of a host animal. They use a sharp bayonet-like tube to pierce a hosts skin to feed on their blood – not nice.
Are House Flies Dangerous?
Yes, in a matter of speaking they are. Control is vital to human health and wellbeing to prevent transmission of pathogenic (disease-causing) microorganisms via cross-infection. Microbes might include viruses, bacteria, fungi, protozoa, and nematodes.
How Do Flies Become Contaminated?
Flies make contact with disease-causing agents while they forage on food waste, sewage, manure and other decomposing material.
Pathogens contaminate their external body parts, mouthparts, and through their vomitus, and faeces.
Both microbiological and physical contamination are synergistic in the contamination of both human and animal food chains.
This disease risk underscores the importance of robust food safety precautions that must begin with fly control and exclusion.
How Do flies Spread Disease?
Houseflies can survive for two to four weeks, providing these flies with plenty of time to become heavily contaminated externally and internally.
When flies feed they vomit onto the material with vomitus rich in proteolytic enzymes to break down the food.
As the flies lap up the digested material, they inadvertently ingest any pathogenic organisms with it.
Pathogens include; Salmonella, Shigella, Campylobacter, E-coli, Enterococcus, Chlamydia, Typhoid, Dysentery, Tuberculosis, Anthrax, Ophthalmia, and Parasitic Worms.
Risks From House Flies
People in high-risk (elderly, young, and convalescents,etc.) groups are particularly at risk of serious medical consequences.
Although we regularly see fly control units and precautions diligently installed and implemented in the food industry, most hospitals and clinics we attend are still far behind with their understanding and implementation of fly control – a worrying thought!
Methods Of fly Control.
Cleanliness: the cleaner and more residue and food resource free an area are the less likely it will be that cross-contamination will occur or that the flies will have reason to remain.
Exclusion: fly screens and other devices that actively inhibit and prevent the access of houseflies into sensitive areas.
Non-Chemical and Mechanical Measures: flypapers, fly swatters, sticky boards and Electronic fly killers are all examples of non-chemical control.
Chemical Control: (when all other methods have failed or been considered) surface insecticides include those that are mixed with sugar and water to create an attractive feeding opportunity.
Once the flies feed they very quickly die.
Other pesticide delivery and treatment methods that are not suitable for food prep areas include fogging and the use of smoke generators.
All will have an effect on these insects, and a combined approach is the best possible way of effectively controlling these flies.
Further Reading Resources
- The House Fly – Penn State University
- Soldier Fly Control of House Flies – Oxford University Press
- House Flies – Nuisance Flies – University Of New Hampshire