When it comes to unwanted guests, none are worse than the kind that eat all your food without asking, stay up all night when you're trying to sleep, wreck your furniture, borrow your clothes, defecate on your floors, and bite you if you get too close. And some of them are sadly unattractive to boot. And they smell.
We're talking, of course, about infestations of insects and rodents.
They're the kind of company for whom most people would happily swap a houseful of alcoholic in-laws who stay a month and boast about having spent nothing.
This is the time of year when the minds of many insect species turn to love, and thence to posterity. They begin mating and egg-laying like there's no tomorrow (which, for many of them, there isn't). And they'll make use of whatever facilities you're careless enough to make available, be it a leftover Chinese takeaway or a conveniently placed blood vessel.
Here's an overview of the top 10 most troublesome infestations, and what to do about them. Some you can manage yourself, whereas for others you'll have to call in the experts.
Unfortunately, the experts agree that the best prevention is to clean your house and garden to the point of neurosis.
False widows and other spiders
The false widow, Steatoda nobilis, is thought to have arrived in Britain in the 19th Century, and it didn't take long for the creature to arrive here.
They're now found all over Ireland, causing acute hysteria wherever they go.
A school in Gloucestershire in England was forced to close last autumn because of an infestation of false widows that were said to be "rapidly multiplying".
False widows, so-called for their similarity to the more dangerous black widow, are venomous and will bite when provoked.
For most people the bite is reportedly no worse than the sting of a wasp, though some people are allergic to it and can suffer more serious symptoms including stiffness in the affected limb and chest pains.
"We've had quite a few queries from people who suspect they have the false widow spider," said Ciaran Murray, technical administrator of Owl Pest Control in Dublin. "People panic, but really you've more chance of getting stung by a wasp."
Other spiders in the home include the common house spider, the wolf spider and the cellar spider – the one that does the samba on the end of its cable when you disturb it. They're harmless, but if you don't want them around you know what to do: spiders like houses that aren't vacuumed often.
Go online to get brush headed grabbers on a stick for lifting them humanely and dropping them outside.
The spread of loose packed imported foods have caused a surge in cockroaches in apartment blocks and Mountjoy Prison is among the complexes which has suffered from the crawlers.
If you turn on the kitchen light at night and hear scuttling, you've got cockroaches.
As well as being unsightly and smelly, they carry typhoid, salmonella and dysentery. They enjoy breeding and are very good at it.
There are three main kinds – the stripey German cockroach, the slightly bigger Oriental cockroach, and the relatively massive American cockroach (everything being of course bigger in America).
If it's a small localised infestation, a proprietary pesticide should work.
But cockroaches are famous for spreading rapidly to adjoining properties, so if you live in a terrace or apartment block, it may not be possible to control them without professional intervention.
"Cockroaches are quite easy to control," said Ciaran Murray. "There are quite good insecticides nowadays.
"The problem is more often about housekeeping issues."
Bed bugs feed on human blood and leave painful bites. People often take them home from holidays as unwitting souvenirs in their luggage.
This means they can occur in even the cleanest households, but the only way to get rid of them is to disassemble the bedding and hoover every centimetre of it, steam clean the soft furnishings and then, after all that, clean the vacuum cleaner itself.
Freezing also kills them. But you may need to get rid of your mattress.
Like cockroaches, bedbugs spread easily from property to property.
For that reason, Rentokil Ireland recommends asking your neighbours if they have bedbugs, which may or may not be a good idea.
It's up to every householder to choose between bedbugs and a decade of frosty relations with the people next door.
Animal fleas make merry in the warm summer weather. They don't live on humans, but they will lay eggs in your carpets and gorge opportunistically on your ankle blood. On the plus side, if you've got fleas because you've got cats, at least you won't have rodents.
Proprietary flea treatments are available, but often won't be enough to annihilate the whole life cycle. You'll have to wash all your pets' bedding and hoover everything – carpets, curtains and soft furniture – like a maniac.
If you're using a household flea treatment against cat fleas, avoid anything containing permethrin. It's dangerously toxic to cats and fish.
Rats and mice
Mice in the house are a common enough problem, and as they're extremely amorous, you can end up with a lot of them very quickly.
Rats represent more of an emergency as they carry salmonella, E. coli, TB and Weil's disease. The epic flooding of the past few winters led to serious rat problems in some urban areas. Ciaran Murray said rodent activity should usually slow down at this time of year, as rats and mice find alternative food sources outdoors. He added: "But for the past few years with exceptionally wet summers, we've been getting a lot of call-outs about rats and mice – rats in particular."
There are good reasons not to tackle a rat infestation yourself: one is the risk of disease, and the other is the danger associated with blood-thinning rat poison.
Both rats and mice gnaw through wood and cables, so there can be a fire risk. The secret is to find out how they're getting in – a young rat can get through a 1cm opening – and stop them. And of course do more cleaning.
Wasps do more than just ruin picnics. A wasp's nest in your attic or under the eaves in an outbuilding will place the area more or less out of bounds, especially if you're allergic to wasp stings.
It is, however, possible to remove a small wasp's nest yourself. It's important to do it early in the year, before the wasps become aggressive in defending their young. Also it's best done in the dark, when they're least active, but this means you can't risk using a torch.
A small nest can be cut off and put in a sandwich bag in the freezer. Freezing temperatures kill wasps. Or you can spray the nest with insecticide. Wasps' nests are vacant in winter, so if you find one, then don't hesitate to knock it down.
Black ants, sometimes called pismires in this country, can be a nuisance in the house, but never more so than in summer when they begin their nuptial flights. They sprout wings and often alarm everybody by turning up indoors in great numbers.
Ciaran Murray said ants are the most common reason for calls to Owl Pest Control at this time of year.
They do bite, but the irritation is said to be minor unless you're allergic.
As they don't carry disease, ants aren't much of a threat. But if you want to discourage them from coming in, what you have to do is – yes, you've guessed it – clean everything, and under everything, so they can't find food.
The woodworm is the larval stage of various wood-munching beetles, including the furniture beetle and the deathwatch beetle.
The problem is not as common as it used to be because, with warmer houses, timbers are drier and less hospitable to the worm. From May to October they begin crawling out of the woodwork.
Treating a half-dozen flight-holes in your coffee table is a simple matter of using an aerosol or liquid woodworm killer. But if there's worm in any of the structural timbers, seek professional help immediately.
If you're organised enough to have different wardrobes for winter and summer, you may notice a moth infestation when you take your seasonal clothes out of storage. On the other hand, if you're as organised as that, you probably won't have moths – they don't like clean clothes.
The larvae of the clothes moth used to die back over winter in the days when all our houses were chilly for half the year. Now, with central heating, they flourish.
It's not just clothes and linens that are susceptible. Moths are also partial to sheep's wool insulation, which could lead to some quite expensive destruction.
Mothballs are no longer recommended, but both cedar and lavender oil can help. And of course vacuum regularly.
Flies can carry salmonella, dysentery, TB, cholera and parasitic worms. They're both unsanitary and stupid.
Everyone gets one or two flies in the kitchen in summer, bashing their brains out two inches away from the open window they just came in.
But if you're plagued by swarms of flies, you need to seek an underlying cause.
A plague of bluebottles may indicate there's something dead in the house, possibly a mouse you dispatched earlier.
House flies feed on decomposing food and animal faeces. That includes the contents of your bin, dog poo in the garden, and bird poo in your guttering.
Blocked gutters and drains near the doors will draw flies into the house. Make sure there's no uncovered standing water outside to draw flies, especially midges. Inside you have to clean all surfaces to make sure they can't find places to lay their eggs.
A new old wives' tale on getting rid of flies is hatched every minute; methods include clove, lavender and basil. One quirky suggestion is hang a vodka bag at the door, as flies reportedly hate vodka. However, there may be better uses for vodka after all that cleaning.