It’s a bad day for arachnophobes: according to spider experts (aka arachnologists), there’s an army of giant spiders about to invade our homes to lay their eggs.

Cue millions of us lining up the old glass and cardboard combo – or quite frankly, doing away with it altogether, as we run away screaming.

Why are giant spiders moving in?

As the weather turns cooler and wetter this month, these giant house spiders, which can grow up to 12cm long, will emerge from as they hunt for female partners.

“Spiders don’t specifically want to enter your home; in fact they’d rather stay away as there’s less food and it’s too dry and clean,” says Simon Garrett, head of learning at Bristol Zoological Society, which runs Living With Spiders phobia courses.

[Read more: Cannibal ladybirds, giant slugs and the other foreign creatures invading our gardens]

“Most species of spider stay outside all the time and never come in houses. However, in autumn, mature male house spiders start to move around in search of mates.

“Although most remain outside, some will move into a house if there is an entry point for them. It is this need to mate that changes their behaviour, so it seems as though they suddenly come from nowhere at certain times.”

What you need to know giant house spiders

While the females rarely leave their nests, and only then to feed, the males are often spotted from now until October wandering around looking for a mate. The females can lay hundreds of eggs and in each egg sac there can be up to 60 ‘spiderlings’.

Like many spiders, these brown bugs seek out corners to build their webs, so you’ll spot them between boxes in cellars, behind cupboards, in attics, near window openings and in other spots where they’re relatively undisturbed.

Unfortunately, there’s not a lot you can do to stop them coming into your house. “If they come across any small opening, they can easily get in,” says Garrett.

“Some people say you can stop spiders by using conkers, but after a short time they dry up and nothing will really repel them fully. The best you can do is make sure there aren’t any leaky pipes or openings.”

But the good news is, these giants prefer to run away than attack humans – and their bites aren’t harmful, although they can sting a little if they manage to pierce the skin.

“Very few species of spider will bite people and of those that try, only a small number can even break our skin,” explains Garrett.

“There are no inherently deadly species of spider found in the UK as their venom is designed for killing much smaller, simpler creatures for food, such as insects.”

Still, they look scary enough to give you nightmares…

Have you spotted any big spiders? Share your stories in the Comments box below.