Noble false widow vs False black widow
These two are easy to mix up. Here's how to tell a noble false widow from a false black widow, and whether either one bites or stings.
Noble false widow
Steatoda nobilis
False black widow
Steatoda grossa
≠The key differences
S. grossa is generally more uniformly dark and lacks the lighter, sometimes patterned dorsal markings often seen in S. nobilis; S. grossa also tends to have a less glossy abdomen.
S. nobilis is typically larger with more distinct cream or pale markings on the dorsal abdomen; S. grossa is usually darker and more uniformly colored.
⚖︎Side by side
| Noble false widow | False black widow | |
|---|---|---|
| To humans | Mildly venomous | Venomous bite |
| Size | 6-14 mm body length (females larger, up to around 14 mm; males usually 6-10 mm) | Females 6-10 mm body length; males 4-8 mm |
| Colours | Dark brown, Purplish brown, Cream | Dark brown, Purplish brown, Pale cream (faint markings) |
| Family | Theridiidae | Theridiidae |
| Habitat | Sheltered, synanthropic locations such as house eaves, garages, sheds, wall cavities and garden outbuildings; also under rocks and in cliff crevices in its native range. | Human structures (houses, basements, garages), sheds, under eaves, rock crevices and debris piles |
| Range | Native to Macaronesian islands; now widespread across western and central Europe, parts of North America, and other regions where it has been introduced. | Originally from the Mediterranean and Macaronesia region; now nearly cosmopolitan, commonly found across North America, Europe and many other parts of the world |
| Active | Active year-round in sheltered indoor sites; outdoors most active in warm months (spring to autumn) and at night. | Active year-round in heated buildings; outdoors most active spring through autumn and mainly nocturnal |
| Pest? | No | Yes |
🔍How to spot a noble false widow
- Rounded, glossy abdomen with variable pale cream or tan markings on a dark brown to purplish background.
- Body length about 6-14 mm with females noticeably larger and more bulbous.
- Messy, three-dimensional cobwebs in sheltered corners of buildings, sheds or eaves.
- Legs relatively short compared with some other house spiders and no prominent long spines.
🔍How to spot a false black widow
- Round, smooth, shiny abdomen; body length 4-10 mm depending on sex
- Uniform dark brown to purplish coloration; may show faint pale markings but lacks bright red hourglass
- Builds irregular, tangled cobwebs in sheltered corners, often near the ground or in undisturbed indoor areas
- Compare size and markings to distinguish from related species (see similar species)
?Frequently asked questions
What is the difference between a noble false widow and a false black widow?
S. grossa is generally more uniformly dark and lacks the lighter, sometimes patterned dorsal markings often seen in S. nobilis; S. grossa also tends to have a less glossy abdomen. S. nobilis is typically larger with more distinct cream or pale markings on the dorsal abdomen; S. grossa is usually darker and more uniformly colored.
Is a noble false widow or a false black widow more dangerous?
Noble false widow: Mildly venomous. False black widow: Venomous bite. Bites are uncommon and occur when the spider is squeezed or trapped against skin. Bites are uncommon and usually occur when a spider is pressed against skin.
Identification from photos is never certain: don't handle insects you can't identify, and get medical advice for bites, stings or allergic reactions.