House Guests, House Pests

Whilst I have commandeered the title of this post from the book by Richard Jones, and whilst I am using his book as part of my research, I am focusing specifically on the pest side of things today.  As is true throughout this month, I will not be looking at spiders… *shudders*

What makes an insect into a pest?

The world is filled with insects, they live everywhere and fill all kinds of ecological niches but we don’t consider them all to be pests.  We value butterflies for their beauty but we consider moths in our home to be a nuisance.  What is the difference?

Well, Richard Jones highlights a crucial divide between our inner and outer worlds, our private homes and the space outdoors.  This invisible line, when crossed, can turn an insect into a pest.  We pay to encourage nature to come closer but we also pay to remove nature when it crosses the arbitrary line of the doorstep.  What seems interesting or magically suddenly becomes unwelcome and disgusting.  The home is a scared space, it’s private and shared only by invitation.  By violating these symbolic boundaries, animals become intrusive.

Why do insects like our homes?

All of the things we value about our homes are the very same things that insects value.  They are looking for somewhere dry to shelter, somewhere warm where food is available.  In winter, for example, butterflies seek the warmth of buildings but then central heating can cause them confusion about the time of year and affect their behaviour.  The same is true for ladybirds.  And wasps and bees can hide in cavity walls until unwittingly disturbed when they may attack.

“Our houses, our food, our belongings and our very existence are under constant attack from a host of invaders eager to take advantage of our shelter, food stores and soft furnishings.”
– Richard Jones

Because of how successfully these insects have lived alongside us, many of them no longer exist in the wild.  They have become so specialised and so well adapted to live in our homes that they cannot survive without us.

When we started wearing clothes 100,000-40,000 years ago, lice evolved to live on us.  There are three kinds; crabs, head lice and body lice.  The latter actually lived in clothes and spread typhus and relapsing fever but is now thankfully rare.  If you could afford a change of clothes you could escape the lice and as such it was something which predominantly affected the poor and reports of 30,000 lice on one person was not uncommon.  It is likely because of these murderous body lice that head lice have such a bad reputation.

Our homes are also an excellent place to find something else that insects like; us.  The blood of mammals and birds is a high protein source and comes helpfully available as a liquid for easy consumption so it is no wonder than some creatures chose to nibble on us.  In mosquitoes, it is the female who goes after our blood and we can’t blame her too much, she needs it to get enough protein for the eggs which are developing inside her.  These vampiric bloodsuckers carefully insert a needle into the bloodstream and have anticoagulant chemicals they use to stop the wound from clotting.  It is the immune response to the chemical that causes itching and swelling but with it they can also transmit malaria, sleeping sickness, the plague, typhus and viruses.  For humans, the amount of blood lost is trivial but the diseases contracted can be deadly.

Another answer to why we have pests in our homes is explained by Danish folklore – the flea was sent to pester mankind as a punishment for laziness!

Today about 3000 animal species pollute human habitations.  This includes obligate parasites such as lice, facultative parasites such as fleas and commensals which are organisms that live with us without harming us or our belongings.  But those which do harm us shape our attitudes to the rest.

Attitudes to pests

It is very revealing that when I was searching google for information on this post most of the results where about extermination or the horrors of insects and creepy crawlies in the home.

As we saw with the lice example, pests and infestations of insects has social meaning and stigma attached and often the presence of bugs in the home is taken as a sign of dirt, of poor living and of laziness even which this isn’t true.  We see pests as symbolising people who are lower in social status than ourselves even though we can all be affected by them – think of how quickly head lice can run through a primary school.

“Scientists have found that some pillows, even in clean houses, are 40% dustmite faeces by weight.”
– Gordon Grice

Towards the end of the 19th century, entomologists who had previously contemplated nature, invoking the creator’s wisdom and artistry, began to view insects as pests in need of eradication.  This was happening alongside the industrial revolution and the discovery of bacteria, which spelled bad news for insects, in particular for house flies.  This also opened up a market for pest control chemicals and it was thus in the interest of industry to perpetuate the negative attitudes to insects.

As time went by, we got more and more sure that humans could and should control nature and Silent Spring is a good commentary on the negative impacts this had.  It was written after the harsh chemicals, developed during the war, began to feature in households and in agriculture.  Through Carson, we get a glimpse into how we perceived, and still perceive, insect life in the western world.  They are very much viewed as something to eliminate.  And some of these attitudes can be seen in words and phrases such as buzz off, stop bugging me, a swarm of teenagers, pests, he’s a cockroach, nitwit etc.

Even where our house guests don’t cause us harm, we still rail against them.  We are precious about our belongings and feel violated when insects nibble on clothing and furniture, somehow the insect existing feels like a personal attack on us.  But of course, some do more than make holes in your favourite jumper.

The danger of pests

Most household insect pests pose little risk unless you happen to be allergic to them.  It’s unlikely to be a problem for you, unless you are not a land dweller, but in 1593, larder beetle larvae nearly caused a ship to sink as the hull had been reduced to honeycomb.

Having said that, some insects are better at killing us that any other animal.  Cockroaches can bite and are attracted to the milk around the mouths of sleeping babies which is pretty unsettling.

“In areas where they pose a serious hygiene problem, roaches outrank even spiders as a focus of phobia”
-Grice

Given that they invade orifices of the human body I think this is a reasonable fear, especially as their legs are covered with bristles which cause immense pain on our sensitive inner body surfaces. Again, they are a vector of disease and the dust they create is the leading cause of asthma in inner city children in the US.

But the deadliest of our enemies, according to Grice, is the fly.  The most dangerous of which is the mosquitoes.  It’s the mechanism by which the mosquito sucks blood which makes it so deadly – there is a regular exchange of blood and saliva and it is this which opens up opportunity for disease to spread.  And this can include malaria which kills over 2 million people a year and makes many more ill.  The most deadly forms of malaria evolved alongside the agricultural way of life in Africa.  People settled in one place, they needed to be close to water, and in doing so they found themselves living near the breeding places of mosquitoes.

More than 40 diseases are spread by flies and they don’t even have to bite us to spread them.  Drinking water invested with eggs is a major reservoir of cholera.  The common house fly spreads at least a hundred different disease causing agents including typhoid, cholera, dysentery and anthrax and can infect us in three different ways; the bristles on their legs and abdomen carry bits of whatever they’ve previously landed on and so by walking on humans can spread diseases, they defecate indiscriminately and digestion is partly exterior – they vomit digestive fluids onto a substance and then suck up the half digested mess.

Another deadly disease spread by insects is the plague.  Through transmission by fleas, this disease which ravaged many people and shaped our culture and history.

In a later post I’m going to look at the ill effects of insects outside the home and we’ll see more ways in which these creatures have shaped human history.  I will also be balancing this out with a look at the benefits of them and of course, we should value all animals for themselves, not for what they do or don’t do for humans.

Further reading:

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