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Insects and other arthropods

How dangerous are spiders?

Poecilotheria regalis, India and Sri Lanka.
Photo: Insectarium de Montréal (René Limoges)
Poecilotheria regalis, India and Sri Lanka.
  • Poecilotheria regalis, India and Sri Lanka.
  • Phidippus johnsoni, Québec, Canada.
  • Latrodectus hesperus, Western North America.
  • Chiracanthium mildei, Québec, Canada.
  • Heteropoda venatoria, cosmopolitan.

Spiders rarely bite humans. Instead, they tend to flee danger. Most of they time, when they bite, it is because the spider accidentally gets stuck between a person’s skin and another object (such as sheets, clothing or shoes) or when people try to catch or handle them with their bare hands.

Are they poisonous? Do they cause allergies?

Almost all spiders produce venom to paralyze their prey before they eat it. However, if a spider does bite, only around 30 of the 47,600 known species of spiders produce venom that is dangerous enough to pose a threat to human health. None of these species live in Quebec.

Certain people can develop symptoms of allergies to spiders. However, this phenomenon is rare and varies from one person to another. Reactions to bites are not associated with the venom itself, but the allergenic proteins in the spider’s saliva. Allergic reactions can also be caused by inhaling hairs, scales or other small parts of the spider. These arthropods do not transmit diseases.

Can spiders sting us?

No, but they can bite us. They do not have stingers like wasps, bees and scorpions. Instead, they have two fanglike appendages called chelicerae, which they use to pierce the exoskeleton of their prey. In Quebec, and all over the world, a spider’s chelicerae are usually too small or fragile to pierce human skin. Spiders that do manage to bite us usually cause only mild pain.

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