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Non-Biting vs. Biting Flies - What Are the Differences?

Rowan Burgess |

The key to good fly control and preventative measures is understanding the different types of flies – biting and non-biting – and their lifecycle.

All flies pose a problem to herd health and animal welfare, with those that bite posing unique challenges and impacting yield and farm incomes. There are also significant environmental problems associated with fly infestations on agricultural premises. We know - not good.

Recognising the different fly species, whether or not they bite, their lifecycle, and how they might affect livestock is an essential part of good animal husbandry. Looking to inform yourself? Learn all about the different fly species in this user-friendly guide. 

Non-biting Flies

We’ll start with the good news. Non-biting flies are of less concern to people keeping livestock, as they don’t cause nearly as much bodily irritation as biting flies. Additionally, a non-biting fly bite won’t cause disease transference. Go ahead - breathe that sigh of relief.

However, fly control is still essential in animal living spaces, as non-biting flies do act as vectors for spreading disease. Drawn in via cattle, sheep, and pig manure, feeding spaces, and dirty bedding, these flies are not something to be messed with.

Physical Appearance

Most non-biting flies in the UK are dark-coloured, usually grey-brown or black - except the fruit fly, a lighter yellow-brown colour.

House flies and cluster flies are up to 10mm long, but bluebottles are significantly more extensive - often twice the size. And fruit flies? We’ve all seen them shaming us for not eating those bananas quickly enough. Fruit flies are quite a bit smaller, hovering at around 3mm in length.


Behaviour and type of flight depend on a few things: species, how and where they feed, and the larval cycle. Non-biting flies tend to cluster around a food source. Compare this with species that bite and feed individually, albeit there may be many on one animal. Yikes!

Examples of Non-biting Flies

House Fly

We surely recognise these friends, as they congregate in all locations - domestic, commercial, and agricultural. They’re attracted to human food, pet food, animal feed, food waste, and animal faeces. In short: they’re hard to miss.

Cluster Fly

Cluster flies tend to keep to themselves and prefer undisturbed areas of animal housing or barns. Like many of us, they’re looking for somewhere warm to hibernate over the winter. 


Named after their distinctive iridescent metallic blue-green colour, bluebottles are also called blow flies. These scavengers are attracted to pet faeces and decaying food. 

Fruit Fly

Fruit flies appreciate rotten or fermenting residues, and they’re commonly found in fruit orchards, breweries, vegetable gardens, and kitchens. They’re yellowish-brown in colour, and they tend to be darker with bright red eyes.

Filter Fly

Filter flies gravitate toward sewage beds and water treatment plants; their larvae feed on organic matter. The filter fly is also known as the drain fly, sewage fly, and moth fly.

Prevention and Control

Fly control programmes should be cyclical and proactively in tandem with insect lifecycle. Indeed, we encourage active insecticide control throughout the fly season for a healthy farm, as well automatic fly control solutions.

Ideally, you’ll want to keep animal housing and bedding as clean as possible. Practise the regular sanitisation of feeding stations to remove old or dry food matter. Flies love unkempt spaces!

We also recommend the regular use of insect control sprays and fly traps as needed. Products with longer residual action provide the best long-term value for your farm.

Let’s move on to biting flies. 

Biting Flies

Physical Appearance

Biting flies have more prominent and well-developed mouth parts, well befitting their hungry role. Commonly dark grey-brown or black, some biting flies - like the horse fly - are larger than a standard house or autumn fly.


Because the target of a biting fly is often moving and resistant to attack, they tend to have a more persistent, if not aggressive, flight. In short, they don’t give up a fight easily! You’ve probably seen it before: a brushed-off horse fly may easily re-attach itself elsewhere on the animal.

Examples of Biting Flies

Horse Fly

While they have a clever name, horse flies don’t only affect horses. They may persistently bite other livestock, causing severe irritation, a loss of condition, and potential yield reduction. 

Only the female bites and suck blood; the males feed from pollen and nectar. Their bite is very painful – to humans, too – with mouth parts that behave like tiny knives and slash the skin with a scissor-type motion. Ouch!

Unchecked, female horse flies will latch on and continue sucking blood until removed by the animal - if they can reach it. 

Horse flies often have colloquial names, which vary in different regions of the country; in Norfolk, they are known as clegs, and clags or breeze flies elsewhere.

Autumn Fly

Autumn flies affect cattle and horses and congregate on the face - often around moisture-sensitive eyes. Interestingly, they harvest protein from nasal mucous and tears, and their tiny teeth stimulate liquid from the eyes. Not a pleasant sensation, indeed. 

Autumn flies don’t just feed on animals but gather on the surface of manure. They also bite people with quite a sharp pinprick sensation. 

Prevention and Control

Biting flies require the same control levels as non-biting flies. These measures include active fly management during the warmer months via fly traps, insecticide programmes, and proper livestock management with hygienic housing.

Also, when needed, it’s essential to protect your stock from the double irritation and pain of persistent bites with topical fly repellent. While it may be impossible to get rid of every fly, keeping the fly population low will reduce the number attacking your innocuous animals.

Likewise, some animals require active and topical fly treatment in certain situations. This list includes newborns - particularly calves - and livestock with an unfortunate allergic reaction to fly bites.

Well-ventilated animal housing and effective farm design also play a role in fly prevention. Bonus: keeping manure and muck away from the stock themselves may provide more immediate relief.

Impact of Flies on Humans and the Environment

Transmission of Disease

How do flies affect humans and other animals? Easy - they carry and transfer pathogens. Indeed, flies are one of the best conveyors of disease within the natural world. 

It’s simple: flies like rotting food, faeces, and manure. Having landed on these gems, they then arrive on your meal - or your body. Species that bite may transfer disease when biting or sucking blood.

This Dracula is merely one of a range of biological vectors. A vector is an organism - frequently a biting insect - which transmits a disease or parasite from one animal or plant to another.

Vector-borne diseases account for more than 17% of all infectious diseases worldwide, causing 700,000 deaths yearly!

Flies may transmit pathogens that cause diseases like cholera, dysentery, typhoid fever, poliomyelitis, and tuberculosis. This is why vaccination is advisable before travelling to hot countries where fly control may be non-existent.

However, flies are truly global citizens - and they have significant impacts on the bottom line. 

Economic Impact

In dairy herds, persistent fly infestations may cause unnecessary stress to cows, affecting food consumption and, consequently, milk yield.

Nasty attacks of horse flies lead to weight reduction in beef cattle and reduced feed utilisation. Additionally, adult horse flies are vectors for disease agents, including viruses and bacteria.

Flies can also negatively impact poultry flocks, causing economic loss from increased disease spread, associated welfare costs, mortality, and food safety issues with egg and meat production. 

House flies and other non-biting flies don’t cause direct injury to poultry, but they do transfer pathogens and other bacteria onto the birds’ wings, legs, and other body parts.

Environmental Issues

Flies have a complex environmental profile - much like humans. They are the original airborne vector and bringer of unwanted diseases, but they also act as plant pollinators fulfilling a critical role in nature.

They mimic bees and are alternate pollinators for various plants, travelling from flower to flower. While not as efficient as bees at carrying pollen, flies act as pollinators for missed plant varieties that bees may not always visit.

The insects we love to hate also act as detrivores, meaning they eat dead organic matter and help with the decomposition process. While prevention is necessary for farms, flies add colour and pollen to an ever-changing world.

Frequently Asked Questions

How Many Types of Flies Are There in the UK?

There are a colossal 120,000 fly species worldwide today, but thankfully, only around a dozen of these are found in the UK. (Phew!) But what fly species lack in variety, they make up in number, particularly during a hot summer.

Which Flies Bite in the UK?

Horse or stable flies bite here, as well as the unpleasant moisture-oriented autumn flies. Keep in mind that midges don’t bite, although they do look quite similar to pesky mosquitos.

Final Thoughts

If you keep livestock, you’re well aware of the menace of flies. Non-biting flies spell trouble, and biting flies harass animals, causing unfortunate diseases and loss of condition.

Fly prevention and control requires 24/7 action and surveillance during the warmer fly season. Likewise, you’ll need targeted planning during colder months to avoid infestations, poor herd health, and veterinary costs.

Dalton Engineering supplies a comprehensive range of high-quality, proprietary fly prevention solutions to work alongside your animal management systems. Together, we can keep your livestock healthy, support animal welfare, protect farm income, and bring peace of mind.