Spider IdentifierBlack widow comparison guide
Black widow traits and common look-alikes
The familiar glossy black adult female is only one widow appearance. Immature females and males can be striped or spotted, while false widows and other cobweb spiders can share a dark, rounded body and an irregular web. Use several visible traits together and keep a safe distance.
Quick answer
Start with several clues
An adult female black widow often has a red or orange hourglass on the underside of a rounded abdomen, but the hourglass can be incomplete, faint or absent. Compare age-related patterning, body form, web, retreat, and broad location. Never turn over or handle the spider to inspect a marking.
Color alone cannot identify a spider. A photo-based result is educational, may be wrong, and is not a guarantee that a spider is safe.
Identification clues to record
Underside marking
The red or orange hourglass is on the underside of the abdomen and varies from connected triangles to separated spots or a barely visible mark. Record it only when it is already visible from a safe angle.
Age and sex
Immature females and adult males may be gray, tan, or dark with white, yellow, or orange spots and stripes. Males are smaller and more elongated than mature females.
Body and web
Mature females have a bulbous abdomen and occupy a sticky, irregular cobweb rather than a symmetrical orb or a dense funnel. Web shape supports a comparison but does not prove species.
Retreat and location
Widows favor dark, undisturbed holes and sheltered spaces near the ground, including wood or stone piles, outbuildings, garages, and utility boxes. Include only a broad geographic location.
Adult females, immature widows, and males look different
Colorado State University Extension describes the mature western widow female as shiny and dark with a rounded abdomen. Its underside hourglass varies widely in shape and intensity, so a perfect red hourglass is not required and black color alone is not enough.
Immature widows and adult males can retain white, yellow, red, or orange spots and stripes on the top and sides of the abdomen. Males are much smaller and have a more elongated form, which means a patterned spider can still belong in a widow comparison.
False widows and other cobweb-spider look-alikes
False widows in the genus Steatoda share a rounded abdomen and irregular cobweb. UC Statewide IPM describes the false black widow as chocolate brown without red coloration on the underside, while Penn State Extension notes that pale abdominal markings can be faint or difficult to see.
Lighting and camera exposure can hide brown tones or pale markings. A dark spider without a visible hourglass remains unresolved when the underside, web, or body pattern is missing from the photo.
- False widows can be dark and rounded, but they lack the red underside hourglass of a true widow.
- Other cobweb spiders may be mottled brown or carry a white band or pale marks on the abdomen.
- Brown widows can range from pale brown to very dark and may resemble immature black widows; their spiky egg sacs are a stronger supporting clue when naturally visible.
Photograph markings without disturbing the web
Never turn over or handle the spider to inspect its underside. Use zoom from outside the web, capture the full body and surrounding retreat, and photograph an egg sac only when it is already visible without moving objects or reaching into a hidden space.
A photo result cannot guarantee that a spider is safe and cannot diagnose a bite. If contact or a possible bite has occurred, use the Safety page and seek appropriate professional guidance instead of relying on this comparison.
- Photograph in neutral light so glossy black, dark brown, and pale markings remain distinguishable.
- Include one wider view showing whether the web is irregular, exposed, near the ground, or connected to a retreat.
- Keep children and pets away while an unknown spider remains in an occupied web or hidden space.
Sources and further reading
- Colorado State University Extension: Western widow spider — Peer-reviewed identification, age and sex differences, web form, habitat, and look-alikes; reviewed August 2025.
- UC Statewide IPM: Widow spiders and their relatives — Hourglass variation, immature widows, brown widows, false widows, and egg-sac distinctions.
- Penn State Extension: False black widow spider — Current false-widow appearance, indoor habitat, and comparison with true widows.