HortFACT
Identification
The adult is dark, mottled with grey and usually 6-7mm long with a 13-15mm wingspan. The transparent wings are folded back over the bode when at rest and the compound eyes are reddish brown in colour. The mouthparts are the ''sponging" type and therefore houseflies cannot bite. The body has a yellowish shade on the side and four dark bands lengthwise on top which are clearly visible in the front. The fourth vein in the wings bends sharply and nearly meets the third vein at the wing margin.
The eggs are pearly white, cylindrical and about 1mm long. They resemble minute pine kernels or rice grains.
The larva or maggot is white, legless and when fully grown about 12mm long. The body consists of thirteen segments arranged to form a shallow cone. The mouth is at the point of the cone. At the posterior end there are two large, black, D-shaped spiracles for breathing. The tough cuticle is thin and flexible.
The puparium is barrel-shaped, over 6mm long and changes during development from yellow through reddish-brown to black.
Hosts
Houseflies are not agricultural pests but are vectors of human and animal diseases. Indeed they are the greatest carriers of dirt and disease known to man. They breed in a wide variety of substrates which provide moist, fermenting or putrefying conditions.
Maggots feed and develop on the manure of all animals, grass clippings, decaying fruit and vegetables and garbage. Adult flies feed on manure piles, sewage, garbage, sputum, food of all kinds and the carcasses of animals. They will also gather round the lips, eyes and nursing bottles of very young children.
Adults can take food only in a liquid state and solids must first be dissolved in their saliva. The adults have a keen sense of smell.
Damage
Houseflies annoy man and his animals and they are extremely important as disease carriers. By crawling over and feeding upon filth, the flies gather disease germs on their legs and bodies and take them into the digestive tract with food. In later visits to human foodstuffs the flies leave behind some of these organisms. Their habit of disgorging some of their food and expelling faeces, both of which may contain germs, thus contaminates food used for human consumption.
Diseases spread by flies include typhoid, diarrhoea, amoebic and bacillary dysentry, cholera, poliomyelitis, anthrax and tuberculosis. They also act as intermediate hosts for roundworms which they transfer to sores and to the lips and eyes of horses. They can also carry tapeworms which infest poultry.
Distribution
The housefly is world-wide in distribution and lives in close association with human dwellings.
Life cycle
| Egg |  |
| Larvae | |
| Pupae | |
| Adult | |
| Days |
Breeding continues throughout the year in warm parts of the country. In colder climates the larvae or pupae over winters and adults enter a resting state (diapause) in sheltered situations.
Mating may occur within 24 hours of emergence from the puparium and one successful mating is sufficient to fertilise the female for her lifetime. Under normal conditions, houseflies are sexually mature in 3-4 days and commence depositing eggs from the ninth day after emergence. Egg-laying may continue throughout the lifetime, i.e. for more than two months. Eggs are laid singly with 100-150 piled up into a mass and 2-7 batches may be deposited by a single female. The average production from one fly may be 500 eggs, however there is a record of 21 batches totalling 2387 eggs laid during 31 days from emergence.
The whole life cycle from egg to adult may be completed in 8-20 days depending on ambient temperature and a new generation may be started anywhere from 2-20 days later. Under favourable conditions the eggs hatch in 8-30 hours and larval development through three instars is completed in 5-14 days. Pupation occurs over 3-10 days and the pre-oviposition period ranges from 2-23 days. Adults may live from 19-70 days. Some 10-12 generations can be completed during the warmer months. A typical life cycle in summer is depicted opposite.
PRITAM SINGH