Cluster Flies

Fruit Flies

Flies are a serious nuisance and transmit diseases such as food poisoning (gastro-enteritis), dysentery, TB, typhoid and cholera – they carry bacteria, vomit digestive juices onto their food to soften and digest it, and lay their eggs in rotten material. They may also carry the eggs of parasitic intestinal worms. The adult is 6-8mm long with a wingspan of 13-155mm. The thorax is grey with dark stripes. The pupa is about 6mm long, and may be yellow, brown or black. The larva is a typical maggot, changing colour from white to cream as it grows. Adult flies live for 1-3 months, depending on the temperature. During her lifetime, an adult female may lay 400-750 eggs in moist or rotting material.

Fly Infestation

Fly infestations are surprisingly common. Inside the house you may find swarms of flies which cling to surfaces, lampshades and plants. They can be very persistent. In this situation it is best to seek expert help for fly control. You should also consider the source – the flies are likely to be inhabiting your house as there are good food sources for them.

How to get rid of Flies

Fly infestations can be treated with various chemical treatments. Professional treatments will tend to be more effective than those bought off the shelf. You can also use electric flytraps for effective fly control.

Treatment for Flies

Food and refuse should be kept sealed and protected, and good hygiene practices followed. Following treatment for a fly infestation, it is best to have a thorough clear out, including behind units or white goods where rotting food may be caught.

Cluster flies are so called because they cluster together in large numbers to hibernate. The clouds of flies can be very unpleasant and leave a strong smell. They can be very difficult to get rid of because of the inaccessible spaces they choose to inhabit for the winter. They will typically find a suitable site that is warm in the winter such as within a wall cavity, roof space, attic room or window frame.

Increasing numbers of cluster flies

The flies are dark greyish colour, about 8mm long with overlapping wings and yellowish hairs on the back. Once they have found a space to inhabit in your home or office, they will emit a pheromone to attract more flies, increasing the size of the group. Where a large group of cluster flies are gathered the smell of the pheromone will be present – it is a sweet cloying aroma. If the site is dry and warm they will come back every winter, with the group increasing in numbers every year.

How to get rid of cluster flies

If your home or office is invaded by cluster flies in the late autumn or winter it can be very unpleasant. To get rid of them, pest control experts will supply an ultra-low volume insecticidal treatment supported by crack-and-crevice treatments. Once the treatment has been applied, to ensure the cluster flies elimination, you should make certain that any opening are sealed.

Lifecycle of cluster flies

After hibernating through the winter in a large group, cluster flies will emerge in the early spring months to warm up and feed. They swarm around garden walls, hedges, fence and roofs taking in the warm sunshine. Spring is the time that the cluster flies will lay their eggs, so after swarming around the garden they will look for a suitable place. Typically they will lay eggs in leaf mulch, compost heaps or other piles of garden debris. The eggs hatch and the larvae will feed and grow.

Parasitic cluster flies

Cluster flies are parasitic insects, choosing earthworms as their hosts. Once the eggs have hatched the larvae will infest earthworms, where they feed on the live host. They will then emerge through the earthworm skin when the host dies and enter the pupae stage in the surrounding soil. After 12-14 days the developed adults leave the soil and fly around in garden areas, looking for nectar in flowers and plants. As the autumn approaches and the weather gets colder they will start to cluster into groups and look for indoor warm spaces such as home or office to invade.


Small flies about 3mm long, with red eyes and a slow, hovering flight. They are associated with rotting fruit and vegetables or fermenting liquids or sour milk. Eggs are laid near the rotting matter, where the larvae emerge to feed for 5-6 days before crawling away to pupate. The entire life cycle can be complete in just 8 days. They can potentially carry disease-causing bacteria onto food products.

Treatment for Fruit Flies

Good hygiene and sanitation is necessary to control fruit flies, plus residual insecticides and electric fly traps.

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