Black Widow Spider

Identification

  • Colour Of most importance, female black widows are best known for their jet black appearance with red markings on the underbelly
  • Size 6 mm to 13 mm long. The adult female is around 12 to 13mm (not including the legs), and the male is about half that size.
  • Description Black widow spiders are all black to brown in colour and differ slightly in appearance based on gender. The female has a red hourglass-shaped marking on the underside of its globular abdomen, while the male black widows have yellow, red and white bands and spots over their backs, as do both sexes of black widows in their immature stages.
  • Notes Only the adult female black widow is dangerous to humans; males and juveniles are harmless. The female black widow will, on occasion, kill and eat the male after mating.

General Facts

Why do I have black widow spiders?

Black widow spiders like to live in a warm climate, in dark, undisturbed locations, typically under stones, in wood piles, under furniture and clutter, and in basements and storage areas. They have also been known colonize freshly disturbed landscapes, such as new-home construction sites. Although not common in Canada, on several occasions they have been brought into the country with produce or shipments from warmer regions of the US. Once inside your home, the carnivorous and predatory black widow spider go on the hunt for woodlice, millipedes, centipedes, and other arachnids, to ensnare in their webs.

How worried should I be about black widow spiders?

Black widow spiders are not aggressive to humans, and only bite when threatened, but their venom is a neurotoxin. This affects the nervous system, causing symptoms, such as, abdominal and chest pain, difficulty breathing, nausea, chills, swelling, sweating, weakness and fever. If bitten by a black widow spider, you should seek immediate medical attention. The female black widow lays approximately 300 eggs. The eggs incubate for some 20 days in a small, round papery sac, that is attached to the mother’s web. After hatching, the baby spiders stay in the cocoon fro up to one month. Due to the risk of painful bites and the spiders' potential for rapid reproduction, it is imperative you take action as soon as you suspect an infestation. Only a professional pest control service will be able to stop a black widow spider infestation in their tracks.

How can I prevent black widow spiders invading?

Reduce clutter in basements and garages by storing items off the floor and away from the wall. Piles of lumber, firewood, stones, or other debris should be moved as far from the home or structure as possible, and stored off the ground. Cut away heavy vegetation and keep tall grasses mowed and trimmed. Repair any holes in brick and exterior stucco. Seal all cracks in the foundation. Use weather stripping around doors and windows. Place screens over vents and other access points. Change outdoor lights to yellow bulbs that deter insects

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