All spiders can bite, though not all spiders can bite humans. Spiders posses fangs (called chelicerae), which they use to capture and kill their prey by injecting venom. Most of the spiders in the world are harmless to humans since their fangs are too small to pierce the skin. However, there are some spiders that should be treated with respect, as their fangs are large enough to be threatening and the toxins in their venom strong enough to be discomforting to humans. According to the British Arachnological Society, there are no species of spider in Great Britain poisonous enough to threaten a human life, but there are several populations of spiders found in the country that can inflict a painful bite to humans if provoked.
False Widow Spider (Steatoda nobilis)
Often mistaken at first glance for the very poisonous Black Widow, the false widow differs slightly in its markings and is not nearly as dangerous. The size of a fingernail, the false widow spider lacks the famous bright red hourglass marking of its venomous counterpart. One is most likely to run into the false widow spider around fences and buildings, where it builds its webs in corners. A bite from this spider is said to be more much painful than a bee sting and can cause significant swelling. Like the black widow, only females are poisonous.
Woodlouse Spider (Dysdera crocata)
Easily identifiable by its black body and monochrome (usually grey to tan) abdomen, the woodlouse spider has a conspicuous pair of fangs and can cause a painful bite. As its name suggests, this spider feeds exclusively on woodlice. It spends its days in a small silk cocoon around woody debris and is most active at dusk, when it emerges to hunt. In Britain, the woodlouse spider is also common in gardens and homes, so its potential to interact with humans is high.
Tube Web Spider (Segestria florentina)
The tube web spider has only six eyes instead of eight and is distinguishable for its six front legs facing forward and its back two racing the rear. Found in walls, trees and around stones, this spider makes a small, tube-shaped web, which it hides in with six tripwire-like strings of web extending outward. The spider sits in its tube and places its six legs on the trip wires, waiting for prey to pass by. The pain caused by the bite of the tube web spider is intense but short-lived.
Water Spider or Diving Bell Spider (Argyroneta aquatica)
The water spider spends its life under the water; therefore, bites by these spiders are a rare occurrence, but they can be extremely painful for a short period of time and can cause feverish symptoms. Found in lakes and ponds all over Great Britain, the water spider builds an airtight web under water, which it then fills with air and uses as a base for hunting aquatic insects. Males are usually larger than females, a characteristic atypical in the spider family.