Flies and Wasps - Preferred Breeding Ground

  • Musca domestica (Housefly) - rubbish tips, moist foods, damp mops.
  • Fannia canicurlaris (Lesser Housefly) - semi-liquid decaying organic matter.
  • Culicidae (Midges and Mosquitoes) - requires water for larval and purpae stages.
  • Pollenia rudis (Cluster Fly) - eggs in soil, larval and purpae stages in earthworms. Adults cluster in roof spaces in autumn.
  • Calliphoridae (Blow Flies, Blue and Green bottles) - meat products, dead animals including rodents.
  • Drosophila spp (Fruit Flies) - fermenting vegetable matter.
  • Psychodidae (Filter Flies) - sewage, wet, rotting material.
  • Ceratopogonidae (Biting Midges) - damp soil, boggy areas.

Control of Fly Infestation

  • Identify the species
  • Locate the breeding sites
  • Instigate removal of breeding sites
  • Insecticidal control measures
  • Use of electric Fly Killers
  • Adults can sometimes be controlled by treatment with fogs or smokes

The identification of species will guide you to the likely breeding sites. Adults can be prevented from entering premises through screening off measures. If breeding sites can be found, these can be removed. This can be virtually impossible in poultry houses, but it has been achieved in intensive animal breeding stations. Locating where adults congregate can lead to nearby breeding sites. Look for fly marks on light and alighting surfaces. Larval food must be moist so look for areas, where this accumulates for example, drainage channels, under equipment. Anywhere where waste food tends to accumulate. Is there a soggy residue in the base of bins? Look in residues for larvae

Encourage removal of breeding sites as a priority. Treat alighting and breeding sites with insecticides. For large numbers of flying insects use Microgen. Sprays of dust are useful in treatment of refuse

Control of Wasps
Wasps (Vespula species) belong to the same order of insects as Ants (the Hymenoptera). They are a highly evolved order of insects with a caste system, where workers (sterile females) build the nests, raise the young and forage for food under the direction of the queen wasp.

All pest wasps have a narrow waist which gives the abdomen great mobility, elbowed antennae, mouth parts with powerful mandibles and fore and hind wings, linked by minute. They also have a characteristic black and yellow colour and the ovipositor is modified to form a sting.

The Importance of the Control of Wasps

  • Prevention of contamination e.g. wasps in food products.
  • Loss of goodwill. Adverse publicity due to prosecution or the presence of wasps in restaurants etc.
  • Prosecution for selling contaminated foodstuffs.
  • Discontent. Staff working in premises infested by wasps are agitated by them.
  • Fear and discomfort. Wasps stings are unpleasant and painful and can be dangerous, especially to susceptible people.
  • There are two common wasp species, Vespula vulgaris (common wasp) and Vesppula germanica (german wasp). Both species prefer to form their nest or colony in the ground, but become pests when they nest in caves, outhouses and cavity walls. Wasps also achieve pest status when they forage for food around waste containers and manufacturing areas of confectionery and preserve factories and cake shops.

Wasp Life Cycle
A single fertilized female or 'queen' begins each colony in the spring. Having mated the previous autumn she emerges from her winter hiding place and seeks a suitable site or nest. This is usually in April, depending upon the weather conditions. The queen scrapes shavings of wood from fence posts, dead trees etc. and chews them to make 'wasp paper'. The wood fragments bound together with adhesive saliva form a thin but strong paper when dry.

The female begins her nest with a few hexagonal cells suspended at the end of a small stalk or pedestal attached to a ceiling or surface. Over this is an umbrella-like cover.

The queen lays her eggs, one in each of these cells. They hatch in 3-5 days. When the larvae emerges she feeds them with fragments of insects she has captured. The life cycle from egg to adult takes between 3 and 4 weeks.

The next generation emerges as sterile workers who take over the work of nest building and food gathering. New cells are formed in a horizontal layer of "comb". When this has reached a certain size a similar layer is constructed, suspended from the preceding layer by short columns of stalks. Six or seven "combs" may be formed and covered by an envelope of paper.

The shape of the nests varies and each cell may be used two or three times. An average nest may produce 25,000 - 30,000 wasps during the season.

In the summer months special large cells are constructed, containing the larvae destined to become "queens". At the end of the summer the "queen" lays unfertilized eggs. Some workers also reproduce without fertilization. These unfertilized eggs all develop into males and mate with the young "queens". Fertilized young "queens" fly away to find a resting-place to hibernate. The rest of the colony dies out in autumn. The nest is never re-used the next year.