Where do the biting and irritating organisms come from?

From outside, through windows and doors:

  • Gnats, mosquitoes
  • Stable flies
  • Thrips

From birds’ nests or nesting boxes:

  • Bird fleas
  • Poultry mites
  • Pigeon ticks
  • Martin bugs
  • Forest flies

From dog or cat, or from their quarters:

  • Fleas
  • Certain mites

From other humans:

  • Itch mite
  • Head lice
  • Body lice
  • Crab lice
  • Human fleas

From foodstuffs:

  • Certain mites

When travelling (in hotel rooms):

  • Bed bugs
  • Fleas

From second-hand furniture or paintings:

  • Bed bugs

From public lavatories:

  • Crab lice

At home, after being in garden or woodland:

  • Animal fleas
  • Ticks
  • Flower bugs

KEY III, insect larvae

With prolegs on the abdomen mealworms or caterpillars

Without prolegs

With powerful, functional legs
Without legs, or with small rudimentary legs

With dense hairs. The rear end with a tuft of hairs dermestid larvae
With scattered hairs, or naked certain beetle larvae

The larva is curled

The larva is not curled

With small legs certain beetle larvae (including powder posttles, furniture beetles and spider beetles),

Legs completely lacking beetle larvae (weevils and bark beetles)

Found in timber, sometimes under bark Found in other places

Broad in front cerambycid larvae
Not broad in front, with spine at rear end wood-boring wasp larvae

Small (less that 5 mm long), with hairs flea larvae

Normally more than 5 mm long, without hairs, but very variable in appearance fly larvae

KEY II, animals with 3 pairs of legs; insects

Wings well developed…………..
N.B. Front wings may be developed as ‘shields’ which cover the flight wings when these are not in use.

Wings lacking…….

Wings small, with hairy fringes. Small animals, less than 2 mm Thrips.

All the wings transparent, possibly with a few hairs

Front pair of wings not transparent

With a single pair of transparent wings flies.

With 2 pairs of transparent wings

Front pair of wings larger than back pair wasps, bees, chalcids, ichneumons, ‘flying ants’,

Wings all about the same size, transparent or smoke-coloured winged termites.

Wings all about the same size, greenish lacewings.

Wings densely covered with scales, which are easily rubbed off butterflies and moths

Front pair of wings as shields which are parchment-like, leathery or hard
Front wings short, covering only front part of abdomen

Front wings covering whole of abdomen, or nearly so

Abdomen in a pair of forceps earwigs.

Abdomen not ending in forceps staphylinid beetles

Front part of front wings leathery, rear part clear and transparent true bugs

Front wings (tegmina) leathery with distinct veins. Antennae long, whip-like cockroaches or crickets

Front wings (elytra) forming hard shields, without distinct veins. Antennae normally short, never whip-like beetles

Elongated, worm-like certain insect larvae

Elongated or plump, with dense hairs certain insect larvae
Not worm-like, and without hairs

With three long segmented ‘tails at hind end silverfish

With a ‘wasp waist’ ants
Without long ‘tails’ and without a ‘wasp waist’

Large animals, i.e. the adults are larger than an ordinary black garden ant

About the size of a black ant, but pale termites

Smaller than an ordinary black ant

With biting mouthparts, and very long whip-like antennae cockroaches
With sucking proboscis, folded in beneath head

Body outline almost circular bed bugs.

Body outline oval, always covered with dust fly bug (nymphs)

Dark, shiny, hard (almost impossible to squash)
Pale and soft (easily squashed)

Sluggish, living as parasites on man and animals lice.
Active, free-living

With a forked springing organ at rear end springtails.

Without a springing organ booklice.

KEY I, animals with 4 pairs of legs; spiders, mites, scorpions etc.

Abdomen with distinct joints

Abdomen without distinct joints

Abdomen elongated, forming tail with sting scorpions.
Abdomen not ending in tail..

Small animals (less than 5 mm),
With claws false scorpions.

Larger animals with very long legs harvestmen.

Body clearly divided into two parts spiders.

Very small animals with undivided body mites.

Key to the Main Groups

Without legs
With three pairs of legs. Often with wings insects
N.B. Newly hatched mites also have three pairs of legs, but they are extremely small, under 1 mm.

With four pairs of legs spiders, mites, scorpions etc.
With more than four pairs of legs.

It may be a slug slugs

It may be a worm worms.

It may be a maggot-like insect larva insect larvae.
With three pairs of true legs, and prolegs on abdomen certain insect larvae.

With 7 pairs of legs woodlice.
With many legs, more than 14 pairs

Flat animals, legs protruding laterally centipedes.

Cylindrical animals, legs attached ventrally millipedes.


Cat flea and human flea

Cat flea and human flea

( Latin: Siphonaptera )

Fleas (Siphonaptera) constitute an order of insects. Their biology is similar to that of flies. Some researchers believe that fleas were once a kind of flies, who lost their wings and adapted to a life as bloodsuckers on birds and mammals.

Fleas are usually the most obvious possibility when insects bite people. In Denmark, there are about 45 different flea species. Each species is more or less dependent on a few specific hosts, in which they live and whose blood they suck. The environment of the host animals’ home or nest is important to the flea larvae development. The adult fleas can suck the blood of other animals than their actual host, and certain animal biting fleas occasionally attack humans. Fleas lay eggs. Small flea larvae emerge from the eggs.

The last of the larval stages spins a cocoon and the adult flea is developed inside the cocoon.


Mosquito, Aedes vexans

Fig. 30. Mosquitoes, the species Aedes vexans (PEUS)

Aedes mosquito - Bedbugs, Bites, Stings and Itches - Page 57

Aedes mosquito

Mosquitoes, of the family Culicidae, are slim, elegant, 5-6 mm long, grayish midge-like flies. There are also some peaceful midges, which are similar to the mosquito in appearance, for example the non-biting midges or chironomids, which are often seen in large swarms over lakes and bays. Mosquitoes are characterized by the long, thin, flexible proboscis on the front of the head, as well as by the fine scales that cover most of the body.

The mosquitoes have long sensory palps. Male mosquitoes have bushy palps, while female mosquitoes have shorter hair on their palps. Only female mosquitoes bite. In Denmark, there are 30 different biting species of mosquitoes, which may bite people when the opportunity presents itself.

Controlling pests in kitchens and food factories

When one has identified a pest species, possibly with the help from the keys, tables and descriptions, the next step is to find out the goods it is likely to attack.

In a factory the control of pests will usually require expert assistance. In a house, on the other hand, one can sometimes do it oneself and the following lines of action are suggested.

a) empty the cupboards and perhaps throw away any lining paper.

b) thoroughly clean all cupboards and shelves, preferably with a vacuum cleaner which can remove insects and dirt from cracks and crevices. Laundry should be properly dried, as damp encourages most pests.

c) examine the goods before putting them back in place. It is usually best to throw away any that are infested.

d) if the goods are only slightly infested or if one has any doubts, it is often possible to save them by warming them in an oven; a temperature of 80° C will kill all stages in the life cycle within a few minutes. The same result can be achieved by putting the goods in a deep freeze for a week.

e) in spite of thorough cleaning it will sometimes be necessary to treat in- accessible cracks and crevices with an insecticide. It is obvious that the strictest precautions must be taken if such substances are to be used in a kitchen or food store. In most cases insecticides based on pyrethrum (p. 219) will be the most suitable for use in the kitchen.

Prevention of damage by pests in kitchens and food factories

As in so many other situations prevention is better than cure, and a kitchen or store should be built so that conditions are as unfavourable as possible for pests. During the actual construction of a building care should be taken to avoid leaving any cavities or cracks in which dust and scraps of food can accumulate and which are too inaccessible for proper cleaning. Such places may be ideal for certain pests. Bookcases and cupboards should either fit tightly to the floor or be free-standing with a clear space below them.

Cupboards and drawers should close properly and it is better to avoid panelling on walls and ceilings with cavities behind. In food factories the covers to machinery should be easily removable, so that frequent and thorough cleaning presents no problem. Foodstuffs must be kept as cool and dry as possible. In a store the goods should not be stacked right up against an external wall, but placed on low racks so that there is ventilation from all sides, and it is possible to sweep underneath them.

Cleanliness is important as dust and waste in cracks and crevices provide favourable breeding grounds for all sorts of pests.

In a kitchen or dining room it is best to store foodstuffs in tight-fitting containers, but there is no guarantee that they have not been infected beforehand. Many pests have an incredible ability to find their way into containers that seem sealed. Foodstuffs should not be kept longer than is absolutely necessary, especially if there has been a previous history of pest infestation in the kitchen. It may be better, at first, to buy food in smaller amounts and to keep those items most liable to attack in the refrigerator until one is quite sure that the pests have been eradicated. As already mentioned (p. 10) pests must come from somewhere and one way of preventing their spread is to go out and look for the source of infestation. In a factory such animals often arrive with raw materials. Suspicious looking parcels should therefore be examined and possibly treated before they come into the work area or at any rate kept separate from the finished goods for as long as possible. Returned goods and packing, empty sacks and containers with production waste are also a common source of infestations. Here again the same principle applies, and they should be kept well apart from raw materials, finished goods and packing material.

Sometimes pests are found in groceries in the house. If such animals are observed in newly purchased items it is in the interests of the grocer to tell him about this so that he can examine his store and isolate any infested goods. In a block of flats the animals may also come from other flats via ducts and piping.

Netting over windows and doors can be very effective in keeping occasional flying insects out of food factories or houses. In cases where the doors have to remain open owing to the volume of traffic it is possible to install a kind of air vent, the opening having a continuous stream of air through which the insects cannot fly.

It will always be easier to keep insects and mites out of food factories if a belt (about 2 metres broad) around the building is kept free of vegetation. If it should be necessary to spray or powder with poison in order to keep away undesirable intruders this can be done in such a belt, without adversely affecting the surrounding fauna.

Rat proofing and eradication

In most civilized countries serious attempts are made to control and eradicate rats, and in some places regular inspection of properties is required by law.

All means of access should be made secure against rats. Windows should either be completely glazed or fitted with galvanized wire netting with a mesh of 1-2 cm, the wire itself having a diameter of at least 0.7 mm. Ventilation ducts opening to the outside should also be fitted with netting. Doors should close tightly and any holes or cracks in the floor and walls should be filled with cement.

Holes made in walls for pipes and ducts must be covered with a close-fitting plate or secured with netting and cement.

Holes should be fitted with rat proof covers, and drainpipes from the roof and outlets from the kitchen sink should also be inspected to ensure that they are not providing access routes for rats.

Rats that manage to get into houses very often enter via the drainage system, either because the drains are old and crumbling, or because the new drains have been installed poorly.

Naturally rats cannot enter if the drains are below a well-cemented cellar floor, but if there is a badly finished join between the floor of a room and the earth they will often manage to dig their way up.

When the presence of rats has been confirmed the normal practice is to put down poison, but if they are under the floors it would be better to catch them in traps, as dead rats produce a dreadful smell.