March 26th, 2020 by Sarah Miles

Any kind of fly is as annoying as hell in your home but unlike houseflies, who tend to come on their own or maybe a pair, cluster flies bring all their mates – thousands of them! Just as the name suggests, cluster flies live in huge swarms and their strength is in numbers.

Technically, they are fairly harmless – they don’t seek out food or excrement to lay their eggs as other flies do so they don’t carry the same risk of spreading disease. However, they do have a pretty funky smell and they can stain your walls plus they can be pretty annoying when you find them around your home.

Where do cluster flies live?

Cluster flies are all about loft living – that’s where they tend to seek out because it’s quiet and warm and usually a big enough space to accommodate them. You may see some elsewhere in the house as a few go astray, seeking out light which they are attracted to.

Why do they come in?

Cluster flies usually live outdoors for the warm summer months, where they mate, but when the weather starts to turn cool they seek warmth and come into our homes. They can enter via open windows or voids in brickwork.

How do you know you have them?

There are a few tell-tale signs that you may have an infestation, even though they’re tucked away in the attic. You may see the odd stray one around the house (they look different to houseflies as they are larger and are slightly yellow or golden in colour). The biggest red flag that you have them is often a sickly sweet odour coming from the loft. This, delightfully, is cluster fly saliva which they deposit onto the walls.

When would you expect to see them?

They’re fair weather flies: while they spend their summer bumming around outdoors, they don’t like the cold so that’s why they seek refuge in your house. Therefore they will start to occupy your home in the autumn time, see out the winter there and then leave again in spring.

If they’re going to leave in the spring, why do I need to get rid of them?

Because, like the Terminator, they’ll be back! This is the greatest issue with cluster flies; that nasty fly spit they rub into your walls has a purpose: it contains pheromone which acts as a marker and allows the swarm to find its way back in the autumn, giving you an annual cluster fly infestation. This means that if you want to break the cycle, you have to get rid of them before they depart on their summer vacation.

How do you get rid of cluster flies?

The two main elements to getting rid of cluster flies are timing and mounting multiple assaults on them. The timing is important because you need to get them before they leave in the summer. If you leave it too late and they’ve already left, they’ll just come back.

What we mean by multiple assaults is that you need to use several different methods of extermination to make sure you get them all. The main issue with cluster flies is that there are just so many so they overwhelm standard fly killing solutions. It’s always best to use products that are specifically formulated for this purpose.

We recommend that you take the following measures:

Automatic aerosol dispensers

Using an aerosol in conjunction with an automatic dispenser means that the insecticide is released at regular intervals into the room. It also means that you don’t have to be up there physically spraying them (nobody wants that job!). We recommend this one from PreVent.

Smoke bombs

Smoke bombs are a really useful remedy for many types of flying insect as they can get into every nook and cranny of the space. This is really useful as it’s vital to make sure you get every single one of them or they could still return once they’ve recruited new friends. Try this one from Fortefog.

Electric cluster fly killers

While regular electric fly killers would kill cluster flies, their trays would fill in no time which could potentially be a fire risk if left. You can, however, get electric fly killers specifically designed for cluster flies with deeper trays and a high capacity zapping grid.

Treat and repeat

Because it’s so important to make sure you get all of them, it’s a good idea to repeat at least one of the treatments a few days later to take care of any survivors seeking to repopulate.