The golden spider beetle

Latin: Niptus hololeucus.
This spider beetle is studded with long golden hair. It infests the same types of products as the first two mentioned spider beetles. When occurring in a warehouse it is often because it has been able to eat dead insects, dry carrions or rodent droppings. The adult golden spider beetles do bite holes in woollen textiles. The beetles are shady, nocturnal, and are active in temperatures down to 5 ° C. The development time from egg to adult is one year at 15 ° C, and half a year at 18-20 ° C.

Wasps

Latin: Vespoides spp.

Hornets - wasps

Hornets – wasps

Season for wasps

Season for wasps

The wasp is a wide category that covers digger wasps, parasitic wasps, hornets etc. Wasps are well known in their black and yellow striped abdomens and no less for their ability to sting. In Northern Europe there are about a dozen species of social wasps, which are very similar to each other both in way of life and appearances.

At our latitude wasp colonies are annual. This means that the nests are only used the year they are built. Old nests from earlier years are empty. It is the young, fertilized queens that overwinter. They wake of hibernation in April and all alone they start the process of founding a new colony. In late May, the first workers are on their wings and then each society steadily grows until August, when there are about 5,000 individuals. The nests are usually spherical. It is built by a paper-like material that the wasps make of wood fibre chewed with saliva. The larvae feed exclusively on meat. Their preys are mostly insects, which the adults catch for them, or it may be chunks of meat that adults bite of carrion. In exchange for the meat chunk that the larvae receive, it regurgitates a sugary liquid up which the adult wasp eagerly eats. The adult wasps primarily live of sugar in the form of nectar, aphid excrement and the like. In the autumn the machinery of their society gets messed up. Workers stops taking care of the larvae and live from that time on by doing nothing until the frost takes them. Most of the summer wasps are not particularly visible. They are busy building their nest and gathering food for their offspring. At that time, they can also get meat from butchers and fishmongers.

In the late summer the wasps become bothersome everywhere. This is partly because the number of individuals now has become quite high and partly because the workers no longer take care of the larvae and they rather find sugar or sweet juice wherever this can be found. It is particularly amongst bakers and greengrocers, at ice cream parlours, etc. as well as place where people eat outdoors.

Hornet, wasp, worker

Hornet, wasp, worker

In businesses and in stores where it is not possible to keep wasps effectively out, light traps with ultraviolet light, where the wasps are captured or killed, clear the problem. The most rational way to fight a local wasp infestation is to find and neutralise the nest. Nests may be sprayed with an insecticide from the bottom up through the entrance hole. You wait until late in the evening when the wasps are all home and are relatively quiet. If the nest is hidden in a cavity wall or in the ground, you can dust the hole or the slot which the wasps fly in and out of, with an insect powder. The wasps will then bring the poison into the nest and a few days later it will be dead. Wasps are aggressive towards people who tamper with their nest, so do not linger at the nest when you fight them. The nest need not be removed.

The pharaoh ant

Latin: Monomorium pharaonis.

Pharaoh ant

Pharaoh ant

Season for Pharaoh ants

Season for Pharaoh ants

A tiny, bright yellow ant. The workers are only approximately 2 mm long. It is originally a tropical species, which has spread across the world through imports. In Northern Europe it has been known since the 1920s.
In Northern Europe, the pharaoh ant depends on heated buildings. The pharaoh ant is most often found in food stocks and businesses, but can also be troublesome in canteens, hotels, hospitals and in private households. All kinds of food may be eaten by this ant. Like the common black ant, the pharaoh ant also has appetite for jam, sugar and honey. Meat products, cheese, high-fat foods, dead insects, carrion and mouse droppings are also among the things that this ant eats. In hospitals, pharaoh ants crawl into sterile products and under the patients’ bandages. Furthermore they seek out waste, carrion and drains, so there is no doubt that the pharaoh ant can carry bacteria to food.

There are usually several queens in a pharaoh ant colony. The colonies are placed in dark cavities near heat sources. Temperatures between 27 and 30 ° C are preferred. There may be several colonies in one building. The colonies live in peaceful coexistence and have some degree of connection with each other.

Pharaoh ant seen from side

Pharaoh ant seen from side

It’s not easy to exterminate pharaoh ants. Start by examining their prevalence so that the extermination can be done throughout the whole infested area. For this purpose, one can lay out pieces of raw pig liver in plastic bags with holes in them or on tin foil. If there are pharaoh ants nearby, they will quickly be attracted to the bait. Knowing their prevalence you can begin the extermination in the outer edges of that area and systematically work your way towards the centre. The extermination itself is to take an insecticide (liquid and / or powder) and thoroughly treat the areas where the pharaoh ants live or move, and into all suspected cracks and crevices. Application of a pesticide in restricted belts in places where the ants have to pass, for example, pipe penetrations, lists, etc. is an addition to the extermination. To exterminate pharaoh ants, a youth hormone-like substance, methoprene, has also been used with success. The method is that the hormone – embedded in a mixture of the ants’ favourite foods – is laid as bait for the foraging worker ants. They bring the mixture into the colony as food for the larvae and queens. The mixture prevents larvae from developing into adult ants and queens lose the ability to lay eggs. The hormone has no effect on the adult worker ants and finished pupae of the colony. Therefore it will take a few months before all the ants have died naturally. These substances only work on insects and are therefore completely safe for humans and pets. One can then add traditional means after a period of a few weeks after the last use of hormone-bait.

The common black ant

Latin: Lasius niger.

The common black ant

The common black ant

Season for black common ant

Season for black common ant

This is the species most frequently encountered indoors. An ant colony usually consists of a dozen thousand ants, and the colony is placed in the ground. In buildings, the ants establish colonies in cavity walls and under floors. Outside, they have a certain fondness for building colonies under tiles. They penetrate anywhere through cracks to seek food. The common black ants live mainly of sweet liquids. In nature they live of aphid excrement, but also various small insects, which they overpower. In private households, shops and businesses the ants especially seek towards sweet and sugary foods. The common black ants hardly have any significance as disease carriers. Often the first signs of ant activity inside, are small piles of sand and gravel, which suddenly appear by panels. These are the ants’ waste piles and one can in the dredged material find insect remains, empty pupae and dead ants.

The most effective extermination will of course be to find and destroy the colonies. Unfortunately, this is often impossible when the ants live inside a building. In those cases you have to experiment with the next best option: to eradicate the adult ants gradually as they show themselves. For this you can use insect powder. Baits with honey and borax can also be effective, but due to the risk of poisoning bees these may only be used indoors. Take one part water to four parts honey and mix well. To 0.5 dl of this mixture, add a teaspoon of borax. It is important that the borax is properly dissolved. You can warm the mixture by shaking it under a hot tap to help that process on its way.

Common black ant, worker

Common black ant, worker

The bait must be set up somewhere that it does not bother having ants crawling around. The ants fill their stomachs with the poisoned honey and distribute it to other ants and offspring in the colony. Provide the ants plentiful before they suspect something. Do not tempt children or pets with this bait by placing or forgetting it in somewhere that they can get to it. Ants on the premises are particularly a spring phenomenon. In summer, they prefer to seek their food outside. However, they still live in or under the building.

The winged ants, which are found in the middle of summer, are males and females which in hot and sultry weather take off on a mating flight. When winged ants occur indoors, it is fortunately only for a short time. You cannot prevent them from flying in, but you can spray with an aerosol containing pyrethrin and then gradually vacuum or sweep the dead ants away.

Hymenoptera

The hymenoptera include ants, wasps and bees. They, like beetles, moths and flies, have complete metamorphosis. The larvae are limbless, blind and pale maggots. There are two pairs of transparent flying wings with relatively few but clear ribs. The rear wings are always smaller than the front wings. Mouth parts are arranged to either suck or bite. In most species, there is a clearly marked narrowing between the first abdomen joint and the following joints. In the rear, the females have a stinger, which for some is used for egg production and for others to sting.

The social hymenoptera, which have the most impact in foods in this country, form communities. The communities share hives, nests and colonies and are composed of males, queens and workers. The workers, which are the most numerous, are small females with undeveloped reproductive organs.

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 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.