MPD3223_VECTOR AND PEST CONTROL: FLIES

True flies are insects of the order Diptera (from the Greek di = two, and ptera = wings). The most obvious distinction from other orders of insects is that a typical fly possesses a pair of flight wings on the mesothorax and a pair of halteres, derived from the hind wings, on the metathorax. (Some species of flies are exceptional in that they are secondarily flightless). The only other order of insects bearing two true, functional wings plus any form of halteres are the Strepsiptera, and in contrast to the flies, the Strepsiptera bear their halteres on the mesothorax and their flight wings on the metathorax.

Types of flies :

TYPES OF FLIES	BLOW FLY	BOTTLE FLY	DRAIN FLY	FRUIT FLY	GNATS
LATIN NAME	Family Calliphoridae	Family Calliphoridae	Family Psychodidae	Family Drosophilidae	Order Diptera Several Families and Species
APPEARANCE	-Metallic in appearance, with feathery hairs on the terminal antennal segments of the males. -Adult blow flies have sponge-like mouth parts, while maggots have hook-like mouth parts.	-Also called blow flies, are common, large flies known for their metallic blue or green color.	-Measure about 1.5 to 5 mm long with a light gray or tan body and lighter colored wings. The body and the wings are covered with long hairs, giving the fly a fuzzy appearance. -When at rest, the drain fly folds its wings over the body in a characteristic roof-like manner.	-Adults are 3 to 4 mm long, may have red eyes, though some are dark eyed, and a tan thorax. -The abdomen is black on top, gray underneath. -Can appear to be brown or tan in color.	- Gnats typically are small and long-legged insects. -They often are weak fliers.
BEHAVIOR , DIET & HABITS	-Attracted to decaying meat and are typically the first organisms to come into contact with dead animals. -The meat of dead animals is essential for larval survival and growth. -Also attracted to plants that give off the smell of rotting meat and as such, can be a pollinator for those plants. -Typically lay their eggs on decaying meat.	-Create a buzzing sound while flying and are scavengers that feed on decaying meat or organic substances. -Transmitters of diseases and are considered to be pests. -Typically found outdoors. If a large number of bottle flies is found inside, an indoor breeding site may have been established. To eliminate bottle flies, it is important to implement stringent sanitation measures, which include cleaning garbage containers and making sure that the lids are seated tightly . -Breed in damp, organic matter such as dead animals.	-In homes, adults are found on bathroom, kitchen or basement walls. -More active at night, drain flies do not bite and, surprisingly, do not transmit human diseases. Drain flies feed on organic matter and sewage. -Eggs are laid in irregular masses almost anywhere decomposing organic materials are found	-Populations tend to build during the summer, becoming very abundant at harvest time. -Indoors, fruit flies are frequently active at all times of the year. -Fruit flies eat ripened fruit and vegetables and fermenting products. -Larvae of fruit flies develop in moist areas	-Contrary to popular belief, these tiny flying insects are not “babies,” they are adults. -The tiny flying insects that many people call “gnats” could really be fruit flies or fungus gnats. -Depending on species, gnats can be biting or nonbiting and will feed on plants, other insects or blood. - Depending on the species, gnat eggs are laid on land or water.

TYPES OF FLIES

HOUSEFLY

The common housefly, Musca domestica, lives in close association with people all over the world. The insects feed on human foodstuffs and wastes where they can pick up and transport various disease agents. In addition to the housefly, a number of other fly species have adapted to life in human settlements, where they present similar problems. In warmer climates, the filth fly, M. sorbens is of particular interest in this regard. It is closely related to the housefly and considered important in the spread of eye infections. Blowflies (Calliphoridae) and other flies have been associated with the transmission of enteric infections.

The house fly, Musca domestica Linnaeus, is a well-known cosmopolitan pest of both farm and home. This species is always found in association with humans or the activities of humans. It is the most common species found on hog and poultry farms, horse stables and ranches. Not only are house flies a nuisance, but they can also transport disease-causing organisms. Excessive fly populations are not only an irritant to farm workers but, when there are nearby human habitations, a public health problem could occur.

LIFE CYCLE OF HOUSEFLY

The house fly has a complete metamorphosis with distinct egg, larval or maggot, pupal and adult stages. The house fly overwinters in either the larval or pupal stage under manure piles or in other protected locations. Warm summer conditions are generally optimum for the development of the house fly, and it can complete its life cycle in as little as seven to ten days. However, under suboptimal conditions the life cycle may require up to two months. As many as 10 to 12 generations may occur annually in temperate regions, while more than 20 generations may occur in subtropical and tropical regions.

Life cycle of thehouse fly, Musca domestica Linnaeus. Clockwise from upper left: eggs, larva, pupa, adult.

Egg: The white egg, about 1.2 mm in length, is laid singly but eggs are piled in small groups. Each female fly can lay up to 500 eggs in several batches of 75 to 150 eggs over a three to four day period. The number of eggs produced is a function of female size which, itself, is principally a result of larval nutrition. Maximum egg production occurs at intermediate temperatures, 25 to 30°C. Often, several flies will deposit their eggs in close proximity, leading to large masses of larvae and pupae. Eggs must remain moist or they will not hatch.

Adult and eggs of the house fly, Musca domesticaLinnaeus.

Larva: Early instar larvae are 3 to 9 mm long, typical creamy whitish in color, cylindrical but tapering toward the head. The head contains one pair of dark hooks. The posterior spiracles are slightly raised and the spiracular openings are sinuous slits which are completely surrounded by an oval black border. The legless maggot emerges from the egg in warm weather within eight to 20 hours. Maggots immediately begin feeding on and developing in the material in which the egg was laid.

The larva goes through three instars and a full-grown maggot, 7 to 12 mm long, has a greasy, cream-colored appearance. High-moisture manure favors the survival of the house fly larva. The optimal temperature for larval development is 35 to 38°C, though larval survival is greatest at 17 to 32°C. Larvae complete their development in four to 13 days at optimal temperatures, but require 14 to 30 days at temperatures of 12 to 17°C.

Nutrient-rich substrates such as animal manure provide an excellent developmental substrate. Very little manure is needed for larval development, and sand or soil containing small amounts of degraded manure allows for successful belowground development. When the maggot is full-grown, it can crawl up to 50 feet to a dry, cool place near breeding material and transform to the pupal stage.

Pupa: The pupal stage, about 8 mm long, is passed in a pupal case formed from the last larval skin which varies in color from yellow, red, brown, to black as the pupa ages. The shape of the pupa is quite different from the larva, being bluntly rounded at both ends. Pupae complete their development in two to six days at 32 to 37°C, but require 17 to 27 days at about 14°C). The emerging fly escapes from the pupal case through the use of an alternately swelling and shrinking sac, called the ptilinum, on the front of its head which it uses like a pneumatic hammer to break through the case.

Prepupa and sequence of puparia by age for thehouse fly, Musca domestica Linnaeus.

Adult: The house fly is 6 to 7 mm long, with the female usually larger than the male. The female and can be distinguished from the male by the relatively wide space between the eyes (in males, the eyes almost touch). The head of the adult fly has reddish-eyes and sponging mouthparts. The thorax bears four narrow black stripes and there is a sharp upward bend in the fourth longitudinal wing vein. The abdomen is gray or yellowish with dark midline and irregular dark markings on the sides. The underside of the male is yellowish.

Adults usually live 15 to 25 days, but may live up to two months. Without food, they survive only about two to three days. Longevity is enhanced by availability of suitable food, especially sugar. Access to animal manure does not lengthen adult life and they live longer at cooler temperatures. They require food before they will copulate, and copulation is completed in as few as two minutes or as long as 15 minutes. Oviposition commences four to 20 days after copulation. Female flies need access to suitable food (protein) to allow them to produce eggs, and manure alone is not adequate. The potential reproductive capacity of flies is tremendous, but fortunately can never be realized.

ADULT HOUSEFLY

General Characters :

The habits of housefly make it eminently suited for the spread of disease. The most important breeding places of flies in order of importance are

(a) Fresh horse manure

(b) Human excreta

(d) Garbage

(e) Decaying fruits and vegetables

(f) Rubbish dumps containing organic matter

(g) Ground where liquid wastes are spilled.

Behaviour of housefly :

The housefly does not bite. It is attracted to food by its sense of smell. It cannot eat solid food it vomits on solid food to make a solution of it and sucks in a liquid state.

Adult flies delight in sputum, faces, discharges from wounds and open sores. The fly is a restless insect and moves back and forth between food and filth. This helps in the spread of infection mechanically. As the fly vomits frequently, the 'vomit drop' is often a culture of disease agents. Flies have a tendency to rest on vertical surfaces and hanging objects.

They have a tendency to fly towards light. Normally houseflies remain close to their breeding places, but they disperse frequently up to 4 miles, and sometimes' even longer from the point of their origin. During the day, flies are mainly gathered on or around feeding and breeding places, where mating and resting also take place (Fig. 6.4). Their distribution is greatly influenced by their reactions to light, temperature, humidity, and surface colour and texture. The preferred temperature for resting is between 35°C and 40°C. Oviposition, mating, feeding and flying all stop at temperatures below 15°C. Flies are most active at low air humidities. At high temperatures (above 20°C), most houseflies spend the time outdoors or in covered areas near the open air.

When not eating, flies rest on horizontal surfaces and on hanging wires and vertically suspended articles and ceilings indoors, especially at night. A detailed study of local resting places is essential for successful control.

Transmission of Disease:

Flies are potential factors of many diseases:

Typhoid and paratyphoid fevers, diarrheas and dysenteries, cholera, conjunctivitis and in fact most diseases that can be spread by mechanical contamination. Flies transmit disease in the following ways:

(i) Mechanical Transmission:

Houseflies are exceptionally efficient mechanical spreaders of disease. They transport microorganisms on their feet and hairy legs. Therefore the houseflies are called ' porters of infection".

(ii) Vomit Drop:

The vomit drop is a rich bacterial culture and by its habit of frequent vomiting, the housefly infects food and thereby transmits disease.

(iii) Defecation:

The excrement of housefly has been found to contain numerous micro organisms as well as cysts and ova of intestinal parasites. By its habit of constant defecation, the housefly spreads these diseases.

Fly Control Measures:

(i)Environmental Control:

The elimination of the breeding places and overall improvement in the environmental sanitation on a community-wide basis is the best way to control houseflies. A clean house with clean surroundings is the best answer to the fly problem.

(ii) Insecticidal Control:

Insecticides such as, D.D.T. B. H. C. Parricides, Baits etc. should be applied to control the houseflies. D.D.T. or B.H.C. may be applied indoors or outdoors using hand or power sprayers. But they produce only a temporary effect on adult fly populations; consequently, repeated applications are necessary. This will be more effective if used for the treatment of fly breeding places. Special care should be taken to prevent contamination of food or water during spraying operations, However, it may be stated that insecticides, at best, only a supplement, but not a substitute for sanitation.

(iii) Fly Papers:

In certain cases sticky fly papers are used to control the house flies. These papers can be easily made by mixing 2 lbs of resin and one pint of castor oil which should be heated together until the mixture- resembles molasses. This should, while hot, be. Smeared on paper by using an ordinary paint brush. Although a slight reduction of flies may occur, no lasting benefits will result from the use of fly papers.

EXAMPLE OF FLY PAPERS

(iv) Protection against flies:

Screening of houses, food markets, restaurants and all other similar establishments will give considerable relief from houseflies. But this, is expensive for general use,

(v) Health Education:

It is difficult to achieve fly control without the willing co-operation of the people. It is only through health education that a fly consciousness’ can be created among the people and they can be motivated with a desire to get rid of flies permanently.

(vi) Sanitation or cultural control :

Good sanitation is the basic step in any fly management program. Food and materials on which the flies can lay eggs must be removed, destroyed as a breeding medium, or isolated from the egg-laying adult. Since the house fly can complete its life cycle in as little as seven days, removal of wet manure at least twice a week is necessary to break the breeding cycle. Wet straw should not be allowed to pile up in or near buildings. Since straw is one of the best fly breeding materials, it is not recommended as bedding. Spilled feed should not be allowed to accumulate but should be cleaned up two times a week. Ordinarily, fly control from 1 to 2 km around a municipality prevents prevents house fly infestations.

Killing adult flies may reduce the infestation, but elimination of breeding areas is necessary for good management. Garbage cans and dumpsters should have tight-fitting lids and be cleaned regularly. Dry garbage and trash should be placed in plastic garbage bags and sealed up. All garbage receptacles should be located as far from building entrances as possible.

For control at waste disposal sites, refuse should be deposited onto the same area as inorganic wastes to deteriorate the capacity of breeding resources, or the disposed refuse should be covered with soil or other inorganic wastes (15 cm thickness) on every weekend or every other weekend.

Around homes and businesses, screening or covering of windows, doors or air doors, and trash containers proves useful in denying access of flies to breeding sites. Packaging household trash in plastic bags, and burying trash under at least 15 cm of soil and in sanitary landfills also helps to eliminate breeding. Trash cans and dumpsters should have tight-fitting lids; failing this, slow release fumigant insecticide dispensers are sometimes installed on the inside of the lids to reduce fly survival.

In agricultural areas, manure can be scattered over fields so that it quickly dries and becomes unsuitable for egg and larval survival. Composting of manure can be effective if the compost is properly maintained, including regular turning. Manure can also be liquefied and stored in lagoons anaerobically, though at some point the solids need to be separated.

(vii) Traps :

Fly traps may be useful in some fly control programs if enough traps are used, if they are placed correctly, and if they are used both indoors and outdoors. House flies are attracted to white surfaces and to baits that give off odors. Indoors, ultraviolet light traps collect the flies inside an inverted cone or kill them with an electrocuting grid. One trap should be placed for every 30 feet of wall inside buildings, but not placed over or within five feet of food preparation areas. Recommended placement areas outdoors include near building entrances, in alleyways, beneath trees, and around animal sleeping areas and manure piles. Openings to buildings should be tightly screened with standard window screen, thereby denying entrance to flies.