Cluster flies can be very problematic pests in homes especially during the colder months. Their “clustering” behaviour caused by operating in large groups can cause distress and unrest.

Learn how to get rid of cluster flies fast and effectively.

What are cluster flies?

Cluster flies are medium sized, about 10mm in length. They are greyish olive in colour and adorned with golden hairs which makes them quite distinctive to the trained eye.

They get their name from their characteristic behaviour of congregating in groups of hundreds and even thousands in lofts, small spaces and around windows.

What causes cluster flies in your home?

During the Winter cluster flies hibernate and don’t typically feed or reproduce.

During this colder period they are known to seek the warmth and light of our homes, typically residing in warmer areas such as lofts, attic spaces and wall voids.

You will often find cluster flies “clustered” around windows or window sills where it can be both light and warm.

How to get rid of cluster flies

There are two main types of products that can be used to get rid of cluster flies...sprays and smoke bombs.

Smoke bombs

Cluster fly smoke bombs are great for tackling entire rooms or areas including lofts and attics as the fumes can reach inaccessible, penetrating all cracks and crevices where cluster flies may be hiding, eliminating them instantly.

Insecticidal sprays

Cluster fly sprays can be used on a multitude of surfaces to neutralise the pheromones and eliminate any visible flies. These lacquer based sprays will also leave a “barrier like” residue behind for future protection.

Signs of a cluster fly infestation

If you believe you may have a cluster fly infestation use these common signs to know for sure.

Visible sightings

The most obvious sign of cluster flies is noticing them congregating in large groups. You may notice them “clustered” together around windows or in more secluded areas such as attics, wall voids and basements.

Sickly, rich smell

If you have a cluster fly problem you may smell a sweet, sickly odour. This smell is omitted from the saliva they deposit on the walls and windows they occupy.

Activity around light

You may notice an increased fly activity around windows and hear increased buzzing noises around light sources. Cluster flies will typically bunch up on windows or light fixtures.

Dead flies

Once cluster flies have entered and settled in your home you may begin to notice more dead flies in the corner of rooms, on the floor or in window sills when cleaning.

How to prevent cluster flies

Cluster flies will typically enter homes through cracks, crevices and other openings around our homes. Sealing these up will help prevent potential infestations especially during the colder months.

Seal up entry points

Cluster flies will typically enter your home through cracks and crevices or even around window frames, especially casement and sash windows.

Inspect your home and seal up obvious entry points. It’s also worth inspecting your lofts or attics for any visible cracks or gaps where they may enter.

Install window screens

Screens can be installed on windows to prevent cluster flies getting inside whilst still allowing air circulation.

Remove attractants

If you live in an area surrounded by grassland and forests you may be more prone to an infestation.

Regularly trimming vegetation and removing earthworms can help eliminate potential attractants towards your home.

Where are cluster flies usually found?

Cluster flies are typically found in and around windows or in lofts and attics. Other places you may find them are within wall cavities, shafts of sash windows, internal frame cavities of double glazed units, wall voids and any other cracks and crevices.

Do cluster flies cause damage?

No, unless they are present in significant numbers. Even though they don’t cause damage they can be of high annoyance due to the large numbers they travel in.

Do cluster flies pose any direct health risks?

Cluster flies have no recognised importance as carriers of disease, so are not a significant pathogenic risk. They should only be viewed as an unsightly nuisance and not as a sign of poor hygiene.

What is important to think about is that cluster flies will hibernate with other flies that ARE carriers of disease, such as blow flies found on faeces and rotting meat, the latter possibly attracted by the smell created by large cluster fly populations.