Fannia canicularis
Small flies repeatedly circling beneath a lampshade or light can be hard to ignore.
In kitchens, pubs and other customer areas, their persistent movement can annoy staff and customers and make the space feel uncomfortable.
These may be lesser house flies, also known as farm flies. They are often associated with farms and other places where suitable breeding material is present. The first step is to identify the fly and consider where it may be coming from.
Why lesser house flies are a nuisance
Lesser house flies often hover or move in repeated loops beneath lights and around indoor spaces. They can gather in kitchens, dining areas and other places where people are trying to work or relax.
Their presence does not necessarily mean they are breeding inside the room. They may be coming from a nearby outdoor source, such as animal waste or other damp, decaying organic material, then entering through open doors or windows.
What does a lesser house fly look like?
Lesser house flies are small, grey flies, usually around 4 to 6 mm long. They are smaller than the common house fly. Males can have three dark stripes on the thorax, though these may be faint.
Their hovering and looping flight can help distinguish them from other flies, but identification from behaviour alone is not certain.
A little about their life cycle
Lesser house flies develop through four stages: egg, larva, pupa and adult.
Eggs are laid in suitable organic material. The larvae develop there before pupating and emerging as adult flies. Animal manure and other damp, decaying material can provide suitable breeding conditions, particularly around farms and livestock areas.
How to reduce lesser house flies
The most useful approach is to exclude them, reduce the conditions that support them and control them where appropriate.
1. Exclusion
Keeping flies outside is often the most effective step. Fly screens for windows and doors, including suitable screened or vented door systems, can help reduce their entry while allowing ventilation.
2. Restriction
Keep outdoor waste and bin areas clean and make sure waste is managed regularly. Where the source may be associated with a farm or other outdoor area, the breeding material may need to be identified and managed.
3. Destruction
Guardian can assess whether outdoor fly bait bags or other suitable measures may help. Where a breeding source is identified, treatment with a larvicide may be considered in more severe situations.
In Guardian’s experience, conventional UV electric fly killers often have little effect on lesser house flies, so they are not usually the main answer. Limited indoor insecticide treatment may sometimes be considered, but it can disrupt customers and staff. We’ll explain the options and any precautions before recommending treatment.
Frequently asked questions
Why do lesser house flies circle beneath lights?
They are often noticed hovering and looping around lights and other indoor areas. The repeated flight can make them particularly irritating in kitchens, pubs and dining spaces.
Are lesser house flies the same as common house flies?
No. They are a different species. Lesser house flies are smaller and are often recognised by their hovering or looping flight.
Where do lesser house flies breed?
Their larvae develop in suitable damp, decaying organic material. Around farms, animal manure can be a source. A fly seen indoors may have come from outside rather than breeding in the room.
Will a UV electric fly killer solve the problem?
It may have little effect. In Guardian’s experience, lesser house flies are not reliably controlled by conventional UV fly killers, so it is important to consider exclusion and the outdoor source as well.
Can Guardian treat lesser house flies?
Yes. We can assess the site and advise on suitable measures. Depending on the situation, this may include screens or door systems, outdoor fly control, treatment of a breeding source or limited indoor treatment.
