giant house spiders invade
Giant house spiders are particularly big this year following the warm wet summerMàrtainn MacDhòmhnaill/Flickr

Giant house spiders with the leg span of small mice are invading homes across the UK, with this year's batch being "particularly big", a spider expert has said. Claire Rind, a reader in invertebrate neurobiology from Newcastle University, told IBTimes UK the larger giant house spiders are mostly found in the south, but have been spreading further north more recently.

The "invasion" of giant house spiders happens every year, she said, adding it is nothing to worry about: "But they are particularly big at the moment. I think because we've had a rather nice warm and wet summer, there have been plenty insects and other invertebrates that the spiders prey on, so they have come in rather early."

Arachnologist Chris Ayre told the Western Gazette people should expect to see these spiders coming inside over the next month. Giant house spiders – Latin name Eratigena atrica – is found across Europe, northern Africa, northern Asia and north America. It is one of northern Europe's largest spider species, with females normally having a leg span of about 4.5cm. Males move inside after their last molt of the year, going in search for females as they become sexually active.

"The males go and hunt the females and they are very insidious in their search," Rind said. "It includes going inside people's houses. The other thing is that with most spiders the females emit a pheromone and they lay it down in their silk so sometimes if the female is inside your house she lays it down a little silk trail that the males can follow."

After mating, the female will normally go back outside to lay her eggs: "Unless she had a really undisturbed dark corner in your house. But it's very unlikely though. They like old walls and stones. As we urbanise they come into more contact with houses.

"It is normal, but there is a giant house spider that is not distributed across the whole of the country but tends to be down in the south sort of spreading north. And these are very large giant house spiders – the leg span of a small mouse, but the body is much smaller than the body of a mouse. They are spreading and that's often what people see when they find a big spider in their house."

Luckily for arachnophobes in Wales, there appears to be a "dividing line" that these larger giant house spiders do not cross: "There are some geographic barriers or some reason why they're not spread everywhere," Rind added.

In terms of being bitten, this should not be a concern. "The thing is not to try to stand on them or hit them with a fist because they you might risk being bitten. The best thing is to put a container over them and scoop them up with a postcard and escort them out. The risk of a bite even inadvertently if you're in the garden is very small."

"If you treat them sensibly [there are nothing to worry about]. People have a deep seated fear but if you are brought up not to fear them you don't. I do appreciate some people have very deep phobias about spiders."