Insects This article is more than 9 years oldHairy, scary and lethal: how dangerous are Britain’s household spiders?
This article is more than 9 years oldThere have been lots of stories about deadly spiders invading the UK, but the arachnids we’re most likely to meet won’t bite. So what should we look out for?Spiders are in the news again. It happens this time every year. Why? Because now is the time for spiders, in their more-or-less annual life cycle, to reach maturity – in other words, their maximum adult size. And yes, some of them can seem very big. They especially grow large when they have had plenty to eat and, being insect predators, they have grown fat on the full and wholesome menu of all those flies and bugs that nice, warm, sunny 2014 has delivered in such abundance.
First, a key fact: all spiders are venomous. That’s how they catch their insect prey, by injecting venom down hollow fangs into their struggling victims. But they don’t really bite humans. We are much too big and taste foul. Think about it. The largest garden spider, seemingly the size of a ping-pong ball hanging ponderously in its web, just cannot get its delicate jaws open wide enough to bite even the daintiest finger. It would be like a human vainly trying to bite a giant pumpkin. Of Britain’s 600 different spider species, just half-a-dozen can open their mouths wide enough, and have fangs long enough to deliver a venomous nip. Despite tabloid horror headlines, it feels like a wasp sting. Even a mild cat scratch can become infected and ooze pus. Deaths from spider bites still hover around the zero mark.
This may not placate nervous householders, though. Once across the threshold, entering the home, domestic invaders are imbued with a menace beyond their still modest size. This is a different group of species from those found in gardens, slightly smaller perhaps, but often longer-legged. They too have benefited from excellent nutritional input this year. Still nothing to fuss about though.
Five household spiders likely to be seen, but still not very likely to bite
House spider (Tegenaria domestica and several similar species)
Appearance: Mottled, often chevron-patterned grey body to 20mm, bristly leg span to over 100mm.
Habitat: Falls in baths, creeps across carpets, these usually males looking for mates. Makes messy, flat-matted web in corners behind furniture, pouncing on insects that dare cross the silk. Harmless.
Daddy long-legs spider (Pholcus phalangioides)
Appearance: Pale short grey body to 10mm in gantry of over-long legs to maybe 100mm.
Habitat: Hangs motionless in feeble, untidy web on cornice or ceiling, but vibrates strands wildly to become a blur if disturbed. Can survive months without food. Good at eating other spiders. Harmless.
False widow spiders (Steatoda nobilis and S. grossa)
Appearance: Globular body to 10mm, legspan to 25mm. Abdomen glossy black variously marked with handsome pale fleur-de-lis, frond or blotch markings.
Habitat: Loose, untidy web in sheds, garages and outbuildings. Unfortunate common name, “rabbit-hutch spider”, would be more appropriate. Can nip if picked up between finger and thumb. So don’t.
Cellar spider (Segrestria florentina)
Appearance: Dark velvet heavily built body to 22mm, legspan to 50mm.
Habitat: Makes retreat in hole in mortar in old wall, picked out by elegant, spoke-like trip-wire silk lines across the brickwork, radius about 60mm. Beautiful bottle-green mouthparts with long fangs that can deliver painful bite. Rare, mostly London and Bristol, old port cities that indicate its Mediterranean origins.
Woodlouse spider (Dysdera crocata)
Appearance: Dusky pink body to 18mm, legspan to 40mm.
Habitat: Under stones and logs with its main prey items – woodlice. Sometimes indoors, in porches or garages. Mouthparts shining pink, with long red fangs necessary to puncture tough crustacean shells. Can deliver painful nip if handled incautiously.
Richard Jones is a naturalist and environmental writer; his latest book, House Pests, House Guests: A Natural History of Animals in the Home, is published by Bloomsbury on 5 December 2014.
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