Pests from A to Z

  • Rokill



These fast moving, minute, cream-coloured or light brown insects, only 1mm long, occur in small numbers in many premises. There are several species, known collectively as Psocids. All have soft bodies. Very few species have wings. They are not related to the parasitic lice (see Lice).

Sticky, pearl-coloured eggs are cemented to damp surfaces and, instead of a larval stage, the insect matures through four recognisable nymphal stages, taking about a fortnight in total.

The adult booklice are believed to feed on microscopic moulds that grow on the glue of book-bindings or on damp cardboard, damp food (especially cereals) or on the surfaces of plaster, leather or wood inside buildings.

They can occur in huge numbers in new properties where the plaster is still damp. One species of booklouse produces an audible tapping noise by banging its abdomen against paper or wood.


Large blundering insects also known as May-bugs which are attracted to artificial light and fly into houses or collide with windows on warm evenings in May and June.

The adult is 20 to 25mm long with a heavily built brown body and wing cases with the tip of the abdomen bent downwards.

Despite a rather formidable appearance, the May bug is harmless and is only a minor agricultural pest.


A long, narrow, brown insect 10 to 14mm long with characteristic “pincers” at one end, the earwig is often carried indoors in cut flowers or house plants and often invades from the garden through open windows, sometimes in large numbers.

Harmless in the house, but it can be discouraged by keeping creepers or vegetation cut back from walls near windows and dusting humid corners where they congregate with an insect powder. A garden insecticide may be used outdoors and on vegetation.


Small (2mm) wingless insects, flattened side to side, red-brown with backwardly directed spines and legs designed for jumping. All adult fleas are parasitic on warm-blooded animals. Larval stages live in the nest of the host and feed on skin, feathers and, most importantly, the blood-rich faeces of the adult flea. When fully grown the larvae spin well camouflaged silken cocoons. When fully developed the adult waits within this until it detects the vibrations caused by a potential host. Only then does it emerge.

The complete lifecycle takes about a month in the summer. Adult fleas feed on blood. Their bites can cause intense irritation around the central bright red spot. Different people react differently to a bite, both in terms of degree of reaction and time taken to react.

The Cat Flea is by far the commonest species of flea and readily bites humans. The Human Flea and the Bird Flea are next in importance. Dog fleas are rare, although other species may become temporarily attached to dogs.

Bird Fleas (Echidnophaga gallinacea):

Bird fleas are ectoparasites commonly found on birds, utilising them as hosts for blood-feeding. While there are various species, one notable example is the "sticktight flea" (Echidnophaga gallinacea), often affecting poultry. These fleas can cause discomfort and irritation in birds, leading to restlessness and decreased egg production. In some instances, bird fleas may bite humans, causing itching and skin irritation.

Cat Fleas (Ctenocephalides felis):

Cat fleas are similar to dog fleas but are more widespread and versatile in their host range. These fleas can infest domestic cats, dogs, and various mammals, including humans. Cat fleas are dark brown to black and possess a laterally compressed body. They are a significant concern for pet owners as their bites can lead to allergic reactions and skin irritation. Effective flea prevention and control are crucial for maintaining the health and well-being of both cats and dogs.

Dog Fleas (Ctenocephalides canis):

Dog fleas are a common ectoparasite that primarily infests domestic dogs but can also affect other animals, including cats and humans. These fleas have a reddish-brown to black color and a flattened body, equipped with specialized mouthparts for feeding on the blood of their hosts. While they can cause itching and discomfort in dogs, dog fleas are highly adaptable and can infest various environments, making effective pest control essential.

Human Fleas (Pulex irritans):

Human fleas are primarily associated with feeding on human blood but can infest other mammals as well. The most common human flea is the "human flea" (Pulex irritans). These tiny, reddish-brown insects can cause itchy bites and may transmit diseases. While less common today due to improved hygiene, human fleas can still be encountered in certain environments, especially those with poor sanitation conditions.

Oriental Rat Flea (Xenopsylla cheopis):

The Oriental Rat Flea is a specific species of flea that primarily infests rodents, especially rats. While its primary host is the brown rat (Rattus norvegicus), it can also infest other rodents. This flea is infamous for its role in transmitting diseases, particularly the bacterium Yersinia pestis, responsible for causing bubonic plague. The Oriental Rat Flea has a laterally compressed body, is dark brown to black, and has powerful hind legs for jumping.


The insect normally referred to as a gnat is actually a small mosquito – correct name: Culex pipiens. It is common in gardens on warm evenings. Another species, the true Window Gnat, is a slow-flying insect about 8mm long with wings more rounded than those of the mosquito.

The wings are strongly veined with dark tips. Eggs of the Window Gnat are laid on rotting fruit or vegetables or other moist food and the larvae may contaminate home-made wines or honeycombs.
It is one of several species known as “filter flies” which breed in sewage filters; so homes near to sewage works may be invaded by them.

Ladybirds (Harlequin)

There are many types of ladybird in the U.K. but quite recently, a new variety was introduced that has the potential to jeopardise the others. See the link on the right for more on this.

The Harlequin ladybird is found naturally in the Far East, including Japan and Korea. It was introduced into several European countries as a predator of pest insects such as aphids, in greenhouses. However it was soon found living ‘wild’ in Belgium in 2001, in Germany in 2003, and in the UK in 2005. Within the UK, it was first reported in the London area, but is now rapidly spreading north and west. At present it appears likely that the Harlequin ladybird will become widely established in the UK.

Numbers of large ladybirds active on the outside of buildings, and sometimes entering buildings, may cause concern to residents. The peak of this autumn activity is restricted to a few weeks only, but once inside wandering ladybirds may occur on mild days throughout the winter. When disturbed, the beetles produce a foul smelling liquid, which may also stain fabrics etc. They do no damage to the building itself.

Being more vigorous than our native ladybird species, there are concerns that it may have a negative impact on their numbers.


Small, flat, wingless, grey parasites about 2mm long with strong claw legs and which feed on human blood. There are two distinct forms of this sort of louse – the head louse and the clothing or body louse, but they are similar in appearance.

The pearly, oval eggs or “nits” stick to hairs or fibres of clothing and the nymphs moult three times before maturing, feeding as they go. The life cycle takes about 18 days. Past epidemics of typhus and trench fever transmitted by lice are now unlikely, but irritating bites can produce impetigo and similar afflictions.

Having lice does not necessarily imply that one is dirty, but the sooner treatment is sought, and the source eliminated, the better.


Most “mosquitoes” seen in houses are in fact the harmless and unrelated Crane Fly. True mosquitoes are very much smaller but have a similar long thin abdomen, long thin legs and strongly veined wings. The head has large eyes and a prominent proboscis. There are two main groups; the Culicine mosquitoes sit with their bodies parallel to the ground, the Anopheline mosquitoes sit “nose-down” to the surface, and most have dark spots on their wings.

The commonest species indoors, often mis-identified as a gnat, is Culex pipiens. It does not bite but is almost indistinguishable from Culex molestus which does!
In the tropics, mosquitoes transmit yellow fever, filariasis, dengue fever and malaria. Even in Britain they cause those familiar itchy bites with a red swelling around them. Near estuaries or marshes, Anopheles maculipennis – a brownish species with small spots on its wings – is fairly common indoors. It bites readily, especially at dusk.

Mosquito eggs are laid in batches in stagnant water and the small brown larvae hang from the surface of the water, turning into comma-shaped aquatic pupae in four to ten days. Within a day or two the adult emerges with a thirst for human or animal blood. Only the females feed and require a blood meal before they can lay eggs. Adult female mosquitoes hibernate in dark corners of houses, sheds, cellars and other sheltered sites.


See Cockchafer


A cigar-shaped, silver-grey, wingless insect about 12mm long, found in damp areas commonly in kitchens and bathrooms. Nocturnal in habit, but often trapped in baths, basins or chinaware as it cannot climb the smooth surfaces. Moves quickly and has three long bristles at the tail end.

Occasionally damages paper but feeds on residues of starchy substances such as glues, wallpaper paste and carbohydrate food debris. It may indicate damp conditions which need attention.

Eggs are laid in cracks and crevices and the nymphs grow by an indefinite number of moults. Can grow a new leg if they lose one. Adults can live for over three years. A closely related species, the Firebrat, is flatter and speckled, without the metallic appearance, and favours hot, dry situations, but can still be destroyed in the same way as its cousin.


Small, wingless insects which usually live in soil but occasionally come indoors, into damp kitchens, cellars and outbuildings. A leaping organ on the end of the abdomen provides the “jump” which gives them their name.


Social insects which may live in communities of many millions of individuals. In tropical and sub-tropical countries they are major pests of timber buildings.

Not presently a significant problem in the UK but global warming may allow them to establish in the south of England.


Woodlice are one of the few land crustaceans. They have oval, grey, segmented bodies 10-15mm long, with 14 legs and prominent antennae. Common names include ‘slaters’, ‘sow-bugs’ and ‘pill-bugs’.

There are three species that enter houses from the garden – one of which, the pill woodlouse, rolls up into a tight ball when disturbed. Woodlice are harmless feeders upon rotten wood or other vegetable matter in cool damp areas.

They normally live underneath stones, clumps of plants, logs, or doormats, from which they may crawl into dark corners of a house. Rockeries with aubrietia are great favourites with them.


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