Big Spider In The House: Is It Venomous And Dangerous?

A large, venomous spider: the “Nosferatu spider”, here with its fangs - the “chelicerae” - clearly visible

If you've found a big, unfamiliar looking spider in your house and wonder if it is venomous and dangerous, there's probably a good chance it's not some lethal "banana spider" that arrived from a tropical country and can kill you with its bite (though of course it could be ;-). The explanation for the presence of your eight-legged guest is more likely to be a little less exciting.

Large spiders that originally felt more at home in the south of Europe can increasingly also be found in more northern latitudes, a good example is the "Nosferatu spider" (Zoropsis spinimana) which has even found its way to London. Another traveler slowly making its way to the north (albeit still relatively rarely seen, but I found one in Switzerland - in my shower of all places), is the radiated wolf spider (Hogna radiata). This species is related to and closely resembles the "tarantula wolf spider", the infamous spider that gave tarantulas their name (even though it's not a tarantula).

The radiated wolf spider looks a lot like the tarantula wolf spider and was originally more at home in the Mediterranean basin, but can now already be found as far north as Switzerland.

Of course these arachnids are - like all true spiders - venomous, but they pose no danger to humans (at most to people suffering from allergies, but those should probably be more concerned about native "dangers" such as bees or wasps). Those big spiders mentioned above are able to penetrate human skin with their chelicerae when they bite, but the same is true for some of the larger native species such as Eratigena atrica (the giant house spider), which can also frequently be found in our homes.

A bite from these spiders can briefly be painful and cause temporary reddening of the skin on the affected area, but as mentioned, this is not dangerous. Furthermore, these spiders are not aggressive and will only bite if provoked (and often not even then). Above all, they are beneficial creatures that keep our homes free of all kinds of annoying bugs.

The Nosferatu spider resembles a wolf spider, but belongs to the Zoropsidae family

The photos were all taken in my garden in Ticino in Switzerland (but I found the spiders in the house; before I released them back into the wild, they had to endure a brief photo shoot :-)

A radiated wolf spider (Hogna radiata) cleaning its chelicerae

In case you're interested, you'll find my best nature photos here