House spiders prefer the shed, shock!

31 October 2010

They may be called house spiders, but these long-legged arachnids, often seen darting across the room at this time of year, prefer to live outdoors in the garage or shed.

One of the long-legged UK house spiders in the Tegenaria genus

One of the long-legged UK house spiders in the Tegenaria genus © Wikipedia Commons

However, between August and October the males of the Tegenaria group of spiders sneak indoors through open windows and cracks under doors, to search for a mate.

During this time they can give a fright to unsuspecting humans, especially if they've fallen into the bath.

House spiders were the top enquiry at the Natural History Museum's Identification Advisory Service (IAS) for August and September.

Many IAS enquirers think the house spider is a foreign species or that they are dangerous. However, they are harmless, although they can sometimes bite if picked up.

Six species of house spider

Adult house spiders are grey-brown with long legs and can be thought of as quite large, by UK standards.

There are 6 species of house spider native to the UK, all in the genus Tegenaria. The leg span of the largest, Tegenaria parietina, can reach over 12cm (5 inches). It is known as the Cardinal spider because Cardinal Wolsey was afraid of them.

The intermediate-sized Tegenaria agrestis and Tegenaria gigantea can only be distinguished by looking at microscopic details.

House spiders feed on flies, beetles, earwigs and cockroaches.

Spider habitat and webs

The natural habitat of the house spider is caves and hollows in trees, but they readily adapt to buildings.

Their cobwebs are permanent and can become quite large, and dusty, if left in an undisturbed corner. They are made up of a silken sheet that funnels into a retreat at the back.

Life cycle

Young house spiders resemble small versions of the adults. They hatch from the egg sac and grow to maturity within a year.

Males usually die in the autumn soon after mating, but many females survive to the next year.

Adult males are distinguished by the sex organs on the ends of the palps that look like a pair of boxing gloves!

Where did they come from

Most of the UK house species were probably introduced during the last few hundred years via imported cargoes from the Mediterranean region.

In Britian, Tegenaria house spiders are expanding their range northwards to the north of England and Scotland.

So, if you'd rather not have a house spider as a guest, get your draft excluders and insect screens out or shut your windows. Or, if you're brave enough, just carefully put them back outdoors.

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