Prevention and control

The larvae, which are scattered in the soil, cannot be eradicated. Insecticides cannot effectively control the adult flies, flying around, either.

Adult horse flies can be trapped in traps, which consist of a rather large, dark object, which can be seen and is heated by the sun. Carbon dioxide (from dry ice) may increase the attractiveness of the trap. The horse-flies that are attracted, are trapped in a trap or in an adhesive that is placed in the trap. If strategically positioned, the trap can help the problem for grazing cattle. As mentioned, horse flies which have strayed indoors – do not bite, but can be controlled with a fly spray with pyrethrin, if you do not just let them out of the windows.

Fruit flies

Latin: Drosophila spp. Also called vinegar flies.

Fruitflies, Drosophila spp

Fruitflies, Drosophila spp

Season for fruitflies

During summer fruit flies live mostly outdoors. In autumn they seek into houses.

Fruit flies are quite rich on species. We know more than 6000 different species, but only a few of them are found indoors. Adult fruit flies are 3-4 mm long, yellowish brown. They typically fly quietly. The larvae are yellowish-white maggots. Pupae almost look like small brown seeds. Adult fruit flies are attracted to the smell of fermenting fruit and vegetables. It is the smell of the various alcohols, formed during the fermentation that they are attracted to. They also like wine, beer, vinegar, milk, ketchup and jam. The females lay their small whitish eggs, which are barely visible, in these foods. Each female lays about 25 eggs per day and up to 1000 in total. The eggs hatch after one day and the small larvae seek into the food. At room temperature, the larvae leave the food and pupate after 4-5 days. In the pupa transformation to adult fruit flies lasts 3 – 4 days. Fruit flies can begin to lay eggs as early as 24 hours after leaving the pupal stage. Under favourable circumstances, at 25-30 ° C the lifecycle is completed within just 10 days.

Fruitfly

Fruitfly

During the summer fruit flies breed in the wild, so one has to be aware of trash cans and compost piles that can act as hotbeds. If fruit flies are a problem for businesses and residential buildings near you, the solution is to dust surfaces of the larval development sites with insect powder. In companies that can and pickle vegetables and fruit must try to effectively block the flies out. In addition, make sure to keep the food, in which flies like to lay eggs, so they cannot get to them. It is easy to overlook how little space fruit flies need to develop. Returnable packaging in the form of barrels, jars and bottles holding slops can cause large fly populations and the same goes for poorly cleaned waste containers. The fruit fly pupae, which almost are cemented to surfaces, are difficult to remove and may give rise to complaints in connection with recyclable packaging. Adult fruit flies are sensitive to the common fly sprays with pyrethrin.

The cheese skipper

Latin: Piophila casei. Also called the meat skipper.

Cheese fly, adult and larvae

Cheese fly, adult and larvae

The small dark cheese skippers lay their eggs in dairy products, meat products and in excrements. Each female lays up to 500 eggs, which are placed in crevices directly in food or in the vicinity of food. At 27-32 ° C the eggs hatch in one day and the newly hatched larvae dig further into the food.

The larvae are 8 mm long and are called jumpers because they have an amazing ability to jump. They do it by doubling up, biting their own tails, tighten the muscles and then just let go. They can easily jump 15-20 cm into the air. The full-grown larvae leave the food and pupate in dark corners or crevices nearby.

The pupal stage lasts 6 – 8 days at temperatures between 25 and 30 ° C. The larvae are not easy to exterminate in foods where poison cannot be directly applied on them. They can live for hours at 50 ° C and up to three days at temperatures below 15 ° C. The full-grown larvae can survive for six months at 9-10 ° C.

The grey flesh fly

Latin: Sarcophaga carnaria.

The grey fleshfly

The grey fleshfly

The grey fleshfly

The grey fleshfly

11-13 mm long, gray striped chest and typically chequered abdomen. Just as the blowfly, the female grey flesh fly also seeks out dead animals to lays her eggs in. Grey flesh fly eggs hatch as soon as they are placed so in principle they give birth to live offspring.

Blowflies

Blowfly

Blowfly

Blowfly season

Blowfly season

The many species of blowflies normally live in the wild. Inside you can meet the heavy, blue-black blowfly, for example the species Calliphora erythrocephala and the slightly smaller, green-metallic shiny gold flies of the genus Lucilia.

Blowflies lay their eggs, the so-called flyblow, in dead animals and other decaying organic materials (excrement, cheese, etc.). The eggs hatch less than a day after they are laid and the larvae bore their way directly into the food. They grow quickly and are only between 4 days and a few weeks to become large enough to pupate. The larvae will then leave the carrion, dig into the soil and pupate there. The pupal stage lasts 1 – 2 weeks. When it is over the adult blowflies hatch and force themselves to the surface and fly away. Adult blowflies can live for a month. You can see them suck on juicy meat and many other kinds of food. Blowflies do not have to come into direct contact with whatever, they will lay eggs on. Females can lay their eggs though a fly screen and tiny holes in plastic and let the eggs fall on the meat. Flyblow hatch and the larvae can develop as long as the temperature is higher than 6-7 ° C.

Two blowfly species

Two blowfly species

Blowflies are generally heavily contaminated with micro-organisms. On average, there are three times as many bacteria on blowflies as on house flies. It is among others the bacteria of the genus Clostridium and Salmonella. Blowflies can smell meat and carcasses at a distance of several kilometres. In industries working with things that tempt blowflies, effective measures must be taken to block them out (see page 164). Blowflies can come from birds’ nests with dead chicks or from dead mice or rats under floorboards or in attics. A single dead rat may provide feed for 4000 maggots. The maggots will, under natural conditions, dig into the soil. When this is not possible they will wander far and wide to find a suitable site for pupation. They have a tendency to seek down and away from light. In containers with meat waste that has been there for too long, you will often see mass occurrences of migrant blowfly larvae. They can in large volumes search across courtyards and find their way in through doors and down basement stairs. This mass invasion is stopped most effectively by dusting with an insecticide powder against creeping and crawling insects. The blowfly larvae are however quite persistent and can survive for several hours before they stop crawling. After the dusting it will in most cases be rational to vacuum, sweep or wash away the dead larvae. In the summer, containers with meat waste must be emptied and cleaned at least three times a week if you want to be sure not to be bothered by maggots.

For use in food companies, including fish and game stores, there are light traps, which are quite effective against blowflies.

The lesser house fly

Latin: Fannia canicularis.

Lesser house fly

Lesser house fly

Lesser house fly, adult and larva

Lesser house fly, adult and larva

The lesser house fly is the typical house fly. It is 5 -7 mm. The males of this species can be seen in a tireless bouncing dance around lamps or other things hanging down from the ceiling. The lesser house fly lays its eggs one by one in very moist, decaying substances, for example, in moist manure or sink drains.

The larvae do not look like ordinary fly larvae. They are flat with a rough, grainy skin and longitudinal rows of thread-shaped, spiny appendages on the joints. The lesser house fly larvae move slowly and are difficult to spot because whatever they live in, sticks to its outgrowths. The pupa resembles the larva much. At 18 ° C development from egg to adult lasts 21 days, and at slightly higher temperatures, 21-26 ° C, it is, not significantly lower, 18 days.

Individual lesser house flies, which may live in birds’ nests, dog excrement, etc., can be found everywhere. Major invasions can almost always be traced back to a chicken or a mink farm. The larvae thrive in chicken or mink manure.

The common house fly

Latin: Musca domestica.

The common house fly

The common house fly

Season for house flies

In spring, there is great interest for advice on how to prevent flies from occurring. In summer, the question is mainly about what to do about the too many flies.

Originates from warm climates, but is now widely spread everywhere. An adult house fly is 8-9 mm long, with a wingspan of 13 – 14 mm. Females seek fresh manure or rotting or fermenting plant material and lay eggs there. The eggs are laid in clumps with approximately 100 eggs and a female lays 10 clumps of eggs in a lifetime. The eggs hatch in 6-8 hours, and the pale limbless maggots seek out places where the temperature is 30 ° C. In pig or calf manure the larvae mature in 3 – 4 days. Then they are approximately 12 mm long and searching for cooler places where they can pupate. Inside the brown, immobile pupae transformation into adult flies happens over a few days and the entire development from egg to adult is completed in about 7 days. After one day the new flies are ready to mate and a day later the females begin to lay eggs. In the lab, you can keep the house flies for six months, but in the European stables their average life span is only a few days. Adult house flies love heat and prefer temperatures between 35 and 40 ° C when choosing habitats. In warm weather, with temperatures above 16 ° C flies can live outdoors where they can lay eggs on the dung heap or sit and bask on walls, and more. House flies are diurnal and they diligently examine their surroundings, especially when they are hungry. They are oriented primarily by sight. The sense of smell also plays a certain role and they can taste through the taste organs that sit on the feet and probosces.

House fly, adult and larva

House fly, adult and larva

Experiments with labelled flies have shown that they can easily fly several kilometres. The flies that hatch where there is plenty manure and feed will mostly stay put. On the other hand, it is a fact that neighbours can get their share of the fly production. Stables and middens, which are the source of houseflies, smell and may obviously annoy neighbours.

Although maggots can develop in kitchen waste, fly infestation in foods are almost always attributed to a stable or manure in the surroundings. In this case measures against flies are primarily aimed at testing whether anything can be done. In practice, however, it is difficult to keep agriculture free from flies. Therefore, one must often supplement the extermination with actions to keep the flies out of the food. Light traps are not effective against house flies. They can catch a few flies, but are worthless for actual extermination. Flies can be exterminated with poison, but not always with success because over time they become less sensitive to the toxins that are used.

Flies

( Latin: Order Diptera)

Flies belong to the two-winged superfamily that with more than 80,000 different species includes all flies and mosquitoes. The two-winged family have one pair of wings. Almost all other insects have two pairs. The small, club-shaped bodies behind the wings of flies and mosquitoes are during escape very active. The wings are similar in function to the rear pair of wings of the other insects. This means that they have no elytrons. The flies that play a role in food have soft probosces.

Flies have complete metamorphosis (see Fig. 3.5). The larvae, known as maggots have no legs. Nor is the maggot’s head visible. The head is very small and averted into the body. Pupation occurs in a capsule, a pupa, which is formed by the exoskeleton of the previous larval stage. Some flies are attracted to food, carrion, excrement and other waste, which means there will always be a risk of them contaminating food with undesirable micro-organisms.

Prevention and control

Season for louse flies

Fig. 44. Louse flies are present from May to August, however they are mostly common in June.

One should not refrain from having birds on the house out of fear for louse flies. The risk of them getting inside the house is, after all, very little. If they show up, they are easily eradicated with one of the usual pesticide sprays with pyrethrin. Treating nest environments with an insect powder will usually stop a louse fly infection.

Life cycle

When louse flies breed, the larvae develop inside the mother, before being deposited to pupate.
Louse flies are mostly found on birds, and sucks blood through a short proboscis. However, the flies are also found in nests where you can also find the overwintering pupae, while the birds have migrated south during the winter. From the nests, the lice flies can sometimes stray into homes. This probably only happens if the birds, for some reason, leave the nest during the breeding season, or if the bird do not return to a nest in which louse flies are overwintering. Louse fly innovations happen in the months from April to August, mostly in June. Furthermore, you can get in contact with louse flies, if you are handling a dead bird. Louse flies rarely bite humans, but their flat body and crab-like walk make them appear rather eerie. They cannot live or multiply in human homes.