Insects have always had a close association with humans.

Even prior to the evolution of Homo sapiens a number of insect species must have already developed an intimate relationship with man's ancestors. Possible candidates for this honour are mosquitos (as prevalent then in swampy habitats, as they are now), and the so-called 'human' flea, which even today is primarily a parasite of hole- and cave-dwelling animals such as the fox and the badger.

The cohabitation of insects and humans dates back at least to when our ancestors evolved from tree-dwellers to inhabit the lakeside, savannah or cave. In addition to those insects already indigenous to the damp recesses of caves, others would have arrived as a result of human occupation.

Elsewhere, the construction of temporary shelters and camps, the collection of wood for fires, and the presence of food and animal hides would have provided many opportunities for insects to find themselves sharing their habitat with those early humans. Certain insects, having become specially adapted to living with early man, will have evolved into distinct species. And the domestication of animals will have added other opportunities for insects to become associated with man.

As the early hominids began to build simple dwellings, insects would have found many opportunities to seek shelter and food within those warm and dark surroundings. Humans have always used natural materials to construct and adorn their dwellings; but even the advent of non-organic materials has not deterred insects from invading modern houses.

Often it is other animals in the house, invited or otherwise, that bring insects with them. Examples of such animals include nesting birds, bat roosts, rats and mice, as well as a range of domestic pets.

The inclusion of house plants has added further opportunities for insects to enjoy the creature comforts of modern living. In turn the presence of insects has provided incentives for other opportunistic arthropods such as spiders to set up home alongside us humans.

A survey of the insect family reveals how varied this association is. Taking a tour of the inside of the typical house in the UK could bring one into contact with many examples of the different orders of insect.

The Kitchen

We shall start our tour in the kitchen, a rich habitat for insects.

The Silverfish

Most of us will have seen the silverfish (Lepisma saccharina). Up to 2cm long, with its unmistakable armour-plated shiny scales, tapered form and long bristle-like antennae, it can be spotted disappearing as we open cupboards late at night. This is a primitive insect which would definitely have inhabited caves of early man. Typically they feed on scraps of paper, glue and spilled food.

The Firebrat

A close relative of the silverfish, the firebrat (Thermobia domestica) - as the name suggests - enjoys the warm surroundings where bread is baked. It feeds on flour.

The Cockroach

If unlucky, we may encounter the Cockroach (Blatta orientalis). These are relatively large, carnivorous insects, reddish-brown in colour. The German cockroach (Blattella germanica) is much smaller and yellow-brown, and can also fly. During the day both types reside under floorboards and in cracks in the wall, emerging at night to consume unprotected meat. Their presence in large numbers, and their characteristic smell, creates a natural antipathy in humans. They readily carry disease, so their appearance in commercial kitchens results in understandable concern. It is also not unknown for the cockroach's larger American cousin (Periplaneta americana) to take up residence, possibly as a refugee from a terrarium¹.

The Ant

The black garden ant (Lasius niger) is the only native ant that makes expeditions into houses, foraging for sugar-based foodstuffs as the colony rapidly expands in early summer.

The pharaoh ant (Monomorium pharaonis), yellow in colour, and the Argentine ant (Iridomyrmex humilis), of a blackish hue, are both smaller than the other native ants and have been introduced from the tropics. Very much a civilising influence in the ant world, they can only be found inhabiting warm buildings, making their nests in wall crevices near food supplies.

The Cellar

Moths

Moving downstairs to the cellar, there are several small moths which inhabit food storage areas. Typical is the flour moth (Pyralis farnalis), the larva of which - as its name suggests - feeds on stored cereals as well as fruit and nuts. The moth which is most likely to be seen is a drab grey-brown colour and, except to expert entomologists, is indistinguishable from many other moths.

Beetles

Many beetles also invade food storage areas. Good examples to watch out for are the eponymous larder beetle (Dermestes lardarius), its relative the bacon beetle (Dermestes maculates), and the grain weevil (Sitophilus granaries).

The aptly-named cellar beetle or churchyard beetle (Blaps mucronata) is also found in most dark places. Mainly a scavenger unless it becomes an infestation.

Flies

The frit fly (Oscinella frit) is only 1.5mm long. It is mainly an agricultural pest, but is found in the autumn in food stores, where the larvae burrow into stored cereals and fruit.

On the other hand, the cheese fly (Piophila casei) is a small shiny black fly which, as the name suggests, enjoys a mature cheddar.

Finally, the vinegar fly or fruit fly (Drosophila melanogaster), beloved by geneticists, is attracted to anything that ferments, from wine to fruit.

The House Cricket

Unlike the other inhabitants, the house cricket (Acheta domesticus) is generally considered by those who enjoy hearing its melodious chirping as 'mostly harmless' (to coin a phrase), although it does attack stored food. Originally a North African species, it is attracted inside by warmth in winter, so that it might survive the unsuitable climate. The female may lay up to 1000 eggs during its lifetime. The nymphs feed on food scraps.

The Living-Room

As we move into the living-room, we can find a number of insects relaxing in the comfortable surroundings also much enjoyed by humans.

The Carpet Beetle

The carpet beetle (Anthrenus sp) enjoys a variety of natural fibres, including carpets, curtains or furs. Look out for the larvae, which are known as 'woolly bears'.

The Woodworm or Furniture Beetle

The woodworm or furniture beetle (Anobium punctatum) is one of several species of wood-boring beetle that infest wood, leaving their mark in the form of neat round holes and a small pile of dust.

The Devil's Coach Horse

You might spot The Devil's Coach Horse (Ocypus olens) scurrying across the floor in the evening. It is a friend rather than a foe, for it feeds on the larvae of other insects such as flies.

The Cockchafer and the Crane Fly

On warm evenings in spring, if the window is open you may be visited by the cockchafer (Melolontha melolontha). In the late summer another frequent intruder is the crane fly or daddy-long-legs (Tipula paladosa). Neither are strictly fellow-inhabitants as such, but they are mentioned here due to their tendency to cause a stir when they bumble around the room.

Flies

No doubt every living-room will be home from time to time to one or more of the many species of larger flies such as the common house fly (Musca domestica) and the bluebottle (Calliphora vomitoria). These insects have followed man to most parts of the world he has explored.

They are considered to be among the worst domestic pests, on account of their capacity to carry and transfer many germs dangerous to man. Any organic material associated with man is likely to be attractive to flies. Their habit of semi-digesting food by first dispersing enzymes in their saliva onto food and then sucking it up makes them particularly effective at transmitting bacteria to humans. Fly eggs are usually laid on decaying material. Under warm conditions, the capacity of the fly to complete its life-cycle within two weeks can cause explosions in its population.

The Library

On the bookshelf one may encounter one of several members of the booklouse family (Troctes sp). It is not only the paper that is attractive to these insects, but also the microscopic mould growing on the pages of old books. Clearly, these insects have evolved to exploit man-made inventions. They would have been present in houses before books made from paper appeared, as they are also found in bark, but this species has made an easy transition from bark to paper.

The Bedroom

As can be expected, some of the insects to be found in the bedroom have more intimate relationships with humans.

The Bed-bug

The bed-bug (Cimex lectularius), at around 6mm in length, has probably one of the most ancient associations with man. It primarily feeds on human blood. Although less common today, it resides in bedding during the day and emerges to attach to humans and feed at night. It has relatives that feed exclusively on specific other mammals, including household pets.

The Assassin Bug

To redress the balance, one should welcome the appearance of the assassin bug (Reuvius personatus), which may take the opportunity to feed on bed-bugs.

Moths

Elsewhere in the bedroom, various species of moth can be found. Typical is the common clothes moth (Tinola bisselliella). Inhabiting the wardrobe or carpet, the caterpillar may be found feeding on fabrics of vegetable origin, such as cotton, as well as hair, fur and silk.

Despite its more exotic name, the fur beetle (Attagenus pellio) and the tapestry moth (Trichophaga tapetzella) do not limit themselves to the more lavish materials, and will happily go down-market and dine out on any fabric of animal or vegetable origin respectively.

The Earwig

It is perhaps appropriate to mention here the earwig (Forficula auricularia) which, as superstition would have it, has a penchant for the human ear. True earwigs sometimes seek the warmth of houses, and they do like dark crevices, but that's as far as it goes!

The Bathroom

While in the bathroom, it is most appropriate to refer to matters of hygiene.

The Human Louse

The human louse (Pediculus humanus) comes in two forms, the head louse and the body louse each remaining faithful to their particular parts of the anatomy.

The Human Flea

The human flea (Pulex irritans) has a long association with man. Originally confined to foxes and badgers, it adopted humans once they began to inhabit caves. The absence of proper hygiene can result in rapid infestation and consequent spread of disease transmitted by the bite of these insects.

Of course, other species of flea also inhabit our furniture, but enjoy the delights provided by our domestic pets instead.

The Attic

Depending on what one chooses to store there, the attic can be prime territory for the infesting insect.

The Death Watch Beetle

More specific to this location is the notorious, but thankfully rare, death watch beetle (Xestobium rufovillosum). The larvae, by tunnelling extensively through the rafters, can reduce them to dust very rapidly. The name derives from the pneumatic-like 'knocking' of the adults as part of the mating call.

The Tree Wasp

Elsewhere in the attic may be found a colony of tree wasps (Dolichovespula sylvestris). Their nests are made of 'paper' produced by scrapings of wood chewed and mixed with saliva to make a pulp, then applied to make a dome-shaped home.

Outside

The materials used to construct the house will dictate which insects might share one's abode.

The Mason Bee

Typically, a brick-built house will be visited by mason bees (Osmia rufa) which excavate holes in the mortar to lay eggs in cells packed with pollen and nectar for their offspring.

The Mason Wasp

The mason wasp (Odyneurus apinipes) has a similar habitat, but their larvae with caterpillars instead.

Termites

There have been reports of colonies of termites (Reticulitermes sp) attacking the damp timbers of old houses on the South Coast from time to time, but the cool climate has thankfully prevented them becoming a resident pest in the UK.

The Ladybird

During the winter, underneath window-sills may be found another 'friendly' insect, possibly hibernating singly or in large numbers huddled together: the seven-spot ladybird (Coccinella 7-punctata).

Butterflies

Other hibernating insects include several species of butterfly, including the peacock (Inachis io) and the small tortoiseshell (Anglais urticae), which produce two or three generations each year. The adult butterfly emerging in the late summer will seek a warm dry corner inside or outside the house in which to shelter for the winter.

Insects Don't Have It All Their Own Way

Ecologists will tell you that if flies were left to their own devices we could find ourselves knee-deep in them within a matter of months following an invasion. Luckily, in addition to several carnivorous insects mentioned already, we have to thank the resident members of several other Arthropod classes for keeping the house in order.

The House Spider

Arachnids are much maligned. The house spider (Tegenaria domestica), at up to 6cm across, dark-brown and very hairy, adds spice to our lives - especially when, curled up on the hearthrug, it makes an unannounced appearance on one of its nocturnal hunting expeditions.

The Harvestman

Another arachnid joining us temporarily in the winter months is the Harvestman (Phalangium opilio). Up to 30mm across, with its unmistakable features, very long legs, and a compact body, it can be seen stalking the open prairies of the house for its insect prey.

The House Scorpion

A close relative of both the spiders and the Harvestman, but very different in appearance, is the ancient order of pseudo (or false) scorpions, such as the house scorpion (Chelifer cancroides). Despite being only 5mm long, with a mean set of pincers resembling the true scorpions, they are a match for most insects of similar size that they might encounter in the environs of the skirting-board.

The Centipede

Another favourite companion of ours is the Centipede, such as the long-legged variety (Scutigera coleoptrata), which is found only in houses. Beware, as it does not reserve its painful bite for insects alone!

Whose House Is It Anyway?

One might believe, in this age of man-made materials and chemical treatments, that humans could call their house their own. Insects will have none of that, however. So despite our best efforts we will be continuing to share our living space with insects. Let's hope that they will in turn continue to tolerate us living alongside them.

Further Reading

• The Amateur Naturalist by Gerald and Lee Durrell is the book that first stimulated the idea for this Guide Entry.

• Highly recommended is the Collins Field Guide - Insects of Britain and Northern Europe by Michael Chinery, 3rd edition. HarperCollins Publishers, ISBN: 0002199181.