Common housefly (Muscadomestica)
Adults are 6-8mm long, with a wingspan of 13-15mm; the thorax is grey with four longitudinal dark stripes; the sides of the abdomen are yellowish and may be transparent; the larva also known as a maggot – undergoes larval moults, gradually increasing in size and changing colour from white to cream; pupa is about 6mm long and may be yellow, brown or black. Houseflies are potential vectors of a wide range of diseases such as dysentery, gastroenteritis and tuberculosis and can also transmit intestinal worms. These flies move from filth to food indiscriminately and may therefore move pathogens from dirty to clean areas. Fly spotting is produced when feeding and defecating.
Lesser housefly (Fanniacanicularis)
Adults are 5-6mm long, with a wingspan of 10-12mm and with a grey thorax, which has three indistinct longitudinal stripes on it; the abdomen has an extensive area of yellow at its base. Potential vectors of a wide range of diseases, such as dysentery, gastroenteritis and tuberculosis, they can also transmit intestinal worms. As with the housefly they may move pathogens from dirty to clean areas.
Fly spotting is produced when feeding and defecating.
Adults are 9-13mm long with a wingspan of 18-20mm; adults are large robust flies with a stout abdomen; the thorax and abdomen are black/blue and dusky in colour. Blow flies are attracted to rotting animal remains on which they lay their eggs. In their search, they can mistake stored meat as a suitable ‘host’. The possibility of disease spread is similar to the housefly.
Flesh fly (Sarcophagacarnaria)
Adults are 10-18mm long with a wingspan of about 22mm; they are bristly grey with three distinct black stripes on the thorax; the abdomen has checkered patterning, which changes according to the angle of view. The hind end of the larva is rounded and the posterior spiracles are sunk into a deep pit surrounded by fleshy lobes. Flesh flies exploit decaying organic matter for larval feeding sites, for example, rotten meat, open wounds, dung and carrion and they will also parasitise insect larvae and molluscs. They can also utilise stored meat as a larviposition site. Carcasses of birds and rodents are used by these flies as food sources for their larvae and therefore adults may be encountered as a nuisance in houses, though they are rarely found indoors in normal circumstances.
Fruit flies (Drosophila spp)
Adult fruit flies are small, yellowish/brown with a darkly striped abdomen; they have prominent compound eyes that are generally red in colour, although darker variants occur; the wings have two clear notches in the front border, which can clearly be seen with a hand lens. Fruit flies are commonly associated with human food preparation and storage areas. They are a source of annoyance in many kitchens, restaurants, etc. They are attracted to alcohol and waste fruit, and can build up to very large numbers when these food/breeding materials are present.
Moth flies (Family Psychodidae)
Adults are 3-4mm long with a wingspan of 10-12mm; they are greyish/brown in colour with wings covered in scales, as is the whole body, giving the fly the appearance of a small moth; the antennae of the moth flies are hairy in appearance with large hairs emanating from the intersegmental junctions. The adult flies are frequently abundant in sewage works. Females lay their eggs in a suitable medium, typically the wet organic matter found in drains. In a kitchen/food processing area these flies are often found breeding in the slime layer in floor traps. As flies are breeding in such areas, there is a possibility that they can transfer bacterial particles. These flies are really only a nuisance pest and not of any great public health significance.
Phorid flies / Scuttle flies (Family Phoridae)
Adults are 3-4mm long with a wingspan of 9-10mm; the thorax is usually dark brown/ tan in colour with a distinctive humped appearance. Phorid flies are found in association with moist decaying organic matter. They are often indicative of blocked or broken drainage systems. The adult flies have a characteristic habit of scuttling in a fast run instead of immediately taking to wing when disturbed, hence their name ‘scuttle flies’. Because they frequent unsanitary sites, there is always the potential of these insects carrying disease-causing bacteria.
General biology and behaviour
Flies have a complete life cycle, consisting of 4 main stages – egg, larva, pupa and adult. The duration of each developmental stage is very much dependent on temperature and food/ moisture availability. All true flies (adult stage) can only ingest liquid food. Should they land on a solid food source, they produce large quantities of saliva together with regurgitated gut contents. The mixture, rich in digestive enzymes, is vomited onto the food together with any living bacteria, viruses and protozoa present in the gut. The resulting liquid food is then sucked back up. This process may be repeated several times during which time the fly may defecate to reduce the overall body weight in readiness for flight. This feeding mechanism underlies the principle mode of food contamination with disease pathogens and spoilage organisms.
Pest status of flies
The fly is a highly mobile pest, able to fly from filth to food carrying with it a wide range of disease-causing organisms on its body. There are many thousands of species of flies; however, relatively few interact with humans. Those that do are among the most destructive of pest species, spreading diseases to man and domesticated animals as well as contaminating food and packaging. The increase and ease of international travel in the air and on the oceans mean that there are very few barriers left to stop the spread of insects worldwide. The mobility of flying insects is the primary reason why their status as pests is so important. This allows them to visit many diverse and contaminated habitats within the course of their relatively short life span. The increase and ease of international travel in the air and on the oceans means that there are very few barriers left to stop the spread of insects worldwide
Home remedies for fruit flies involve cleaning and removing any food or rotten produce. A spray window cleaner or water and bleach can be used to clean the areas where fruit flies gather. The cleaner and bleach will kill the fruit flies. Some fruit juice or wine left in a small bowl will attract the fruit flies. They will fall into the bowl and drown. Lavender oil on a sponge and placed in areas with fruit flies is another good home remedy.