Project Description

clusterfly2Cluster flies are found all over North America and earned their name from their clustering behavior before and after hibernation. They are larger flies, 8-10 mm long, dark grey with a black and non- metallic silver checker pattern on their abdomen and are easily identified by the gold hairs on their thorax(back).

They are attracted to light and can be considered a pest because of the stains they leave on curtains and walls when they emerge from hibernation and seek out light, clustering around windows. Their hibernation sites are generally in hidden areas of homes such as wall voids, attics, closets and empty rooms. Dead flies in wall voids attract other invaders such as larder beetles, spiders and centipedes which can spread to other areas of the home and become pests themselves. If a group of hibernating flies is disturbed, they emit a sickly, sweet odour.

Adult flies spend the warm days of summer outside and do not feed inside the house like other house invading flies, instead feeding on the nectar of flowers.

Cluster flies mate in spring and lay their eggs in the soil. The eggs hatch 3-7 days later and the larvae tunnel into the bodies of earth worms and feed on them until they emerge as adults in mid-summer. In late summer, the cycle is repeated with larvae overwintering in the bodies of earthworms.

Cluster flies can be seen sunning themselves on the side of homes in the fall before they go into hibernation. This is an indication that you are going to have problems with them in the future.

They are more common in rural areas due to the open fields and presence of more earthworms, equalling more breeding sites.

Spring and fall exterior treatments are the best way to control cluster flies. In extreme cases, summer treatments may be required.

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