We are all used to having one or two houseflies pay us an uninvited visit over the summer months. Whilst they can be quite annoying, they are not usually too much of a problem. Cluster flies, on the other hand, can be considerably more problematic.
There are 8 species of cluster flies found in Britain, the most common being Pollenia Rudis. Cluster flies gained their common name as the adults congregate in large numbers inside buildings, often on warm windows on sunny days or hibernating in clusters in roof spaces.
With cluster flies, even if you have only seen a few, the chances are there will be many, many more, with a possible infestation somewhere in your home; often eaves, fascias and attic spaces.
They are found throughout the UK and become a real pest in autumn, especially for rural areas, when they occupy buildings over winter.
They are next a nuisance when they become active again, returning outdoors to lay eggs during springtime after the weather becomes warmer. Whilst they are harmless t
o human health and do not bite, they are difficult to live with because of their sheer volumes; heavily infested buildings can house several thousand cluster flies!
Cluster Fly Identification
There are several cluster fly species, varying slightly in colour and size, but the most common variety you are likely to encounter are dark grey, with golden yellow hairs on the thorax, and a dark and light chequered pattern on their abdomen. Cluster flies are around 7mm in length and have overlapping wings at rest.
They typically move slowly in flight and are a seasonal pest, so stay vigilant during autumn, and again in spring.
They can be seen earlier if you keep your home very warm over winter, which can mislead them into coming out of hibernation early.
Prevention and Treatment
- Identify and seal entry points! Unfortunately, cluster flies can return to the same location year upon year. Use caulking around window and door frame edges, and other wall crevices to help hinder their entry into your building in the first instance.
- Suck it up! Use your vacuum cleaner to physically remove them from your property, reducing their numbers.
- Many Pyrethroid-based sprays and electric fly killers used at times of cluster fly activity can be effective in managing smaller numbers of exposed flies.
- Pest control contractors may use Permethrin-based smoke formulations or insecticidal fogs which may prove successful to clear heavier infestations.
- BAT CHECK FIRST! Due to the dramatic decline in their numbers, all bat species, their breeding sites and resting places are protected fully by law. Avon Pest Control strongly urges you to ensure that there is no presence of bats before you go ahead with any smoke treatments or install an electric fly killer. We recommend contacting a professional. Professional exterminators will know what signs to look for to make sure you do not unintentionally break the law
If cluster flies are causing you a problem, give Avon Pest Control a buzz on 01926 632 929 for professional advice, information, and removal or treatment pricing.