What is a false widow?
False widows are spiders in the genus Steatoda, family Theridiidae — the same family as true black widows (Latrodectus). The 'false widow' name reflects the superficial resemblance: both are dark, round-bodied, cobweb builders. But they're distinct genera with different venom compositions and very different medical significance. The confusion is purely cosmetic.
In Metro Vancouver, the two most commonly encountered species are Steatoda grossa (noble false widow — native to parts of Europe, widely introduced globally) and Steatoda nobilis (which has been expanding its BC range along the coast since the 2010s). Both species are established outdoor-to-indoor residents. Steatoda grossa is the one most commonly found in garages, basements, and outbuildings. Steatoda nobilis tends toward slightly warmer microhabitats — south-facing walls, fences, covered exterior areas.
| Species | Colour | Size | Distinctive mark | Web location |
|---|---|---|---|---|
| Steatoda grossa (noble false widow) | Dark brown to purple-black | 6-10 mm female | Pale front band on abdomen | Dark corners, basements, garages |
| Steatoda nobilis (noble false widow) | Dark brown | 8-14 mm female | Cream/grey skull-like pattern on abdomen | Exterior walls, fences, covered areas |
| Steatoda triangulosa | Brown with triangular pattern | 4-6 mm | Triangular abdominal pattern | Lower walls, corners |
| Black widow (Latrodectus hesperus) | Jet black, shiny | 8-10 mm female | Red hourglass UNDERSIDE only | Ground level, sheltered corners |
How to tell a false widow from a black widow
The key distinction is the red hourglass marking on the underside of the abdomen — this is the black widow's defining feature and false widows don't have it. Steatoda species have abdominal patterns that may include pale bands, mottled markings, or a cream pattern, but nothing that looks like a red hourglass. In terms of appearance, false widows tend toward dark brown rather than the jet black of a true black widow female. The black widow's abdomen is also notably rounder and more prominent — a teardrop shape — compared to false widows, which have a somewhat flatter abdomen relative to total body size.
Practically: if you flip over the rock, log, or furniture piece and see a shiny black spider with a red hourglass visible on the underside of its abdomen, that's a black widow. If you see a dark brown spider with a patterned abdomen but no red hourglass, it's almost certainly a false widow. When in doubt, don't handle either.
The bite reality: what media gets wrong
UK tabloid media ran multiple 'false widow crisis' stories between 2013 and 2020, attributing necrotic bites, hospitalisations, and terrifying symptoms to Steatoda nobilis — which had been expanding its range in the UK at the same time. The medical picture that emerged from actual toxicological research was considerably more modest. Steatoda bites produce what is called steatodism: a local reaction with pain that can be significant (described as similar to a wasp sting, sometimes more intense), sometimes radiating beyond the immediate bite area, lasting from a few hours to a day. Occasional cases include sweating and nausea. These are real symptoms and more significant than a typical house spider bite.
What steatodism does not produce: tissue death (necrosis), hospitalisation in healthy adults, systemic effects comparable to black widow latrodectism, or life-threatening reactions. The UK cases that were reported as serious hospitalisation events typically involved secondary bacterial infections from the wound, not the venom itself — the same misattribution problem that inflates spider-bite severity across all species.
Where to look for false widows in Metro Vancouver
- Garage corners and underside of shelving: Steatoda grossa commonly establishes in garages, particularly near floor level. Webs in lower shelf corners, under workbenches, in utility shelving.
- Basement utility rooms: the cool, undisturbed corners of utility rooms are occupied by both Steatoda and European house spiders. The false widow's web is coarser and more irregular than the house spider's funnel.
- Exterior south-facing walls: Steatoda nobilis particularly favours exterior wall locations with sun exposure — brick, wood siding, exterior fence panels.
- Outdoor furniture storage: false widows regularly occupy the gaps under stacked garden furniture and inside furniture storage boxes.
- Crawlspace entries and vent frames: any gap or enclosed structure at low level on the exterior.
Management: when to act
False widows in Metro Vancouver warrant management in the same situations that other non-widow spiders do: high density near occupied living spaces, egg sac presence in entry vectors, or situations involving vulnerable occupants (children, immunocompromised individuals). They don't warrant the emergency response appropriate for black widows. Treatment is the same standard perimeter pyrethroid application used for house spiders — false widows are not significantly more resistant to registered products.