Many spiders resemble black widows, leading to frequent misidentification and concern. Understanding a true black widow’s features and how they differ from other dark spiders is important for accurate identification. This article clarifies black widow characteristics and distinguishes them from common mimics.
Identifying True Black Widows
True black widow spiders, particularly females, possess several defining characteristics. Female black widows typically have a glossy, jet-black body, a hallmark feature. Their abdomen is distinctly globular and rounded, often described as spherical or “shoe-button” shaped.
A prominent red or reddish-orange hourglass marking is located on the underside of the female’s abdomen. This marking can sometimes appear as two separate triangles or be faded.
Female black widows typically range from 8 to 13 millimeters (about 0.3 to 0.5 inches) in body length, excluding their legs. With legs extended, they can appear larger, reaching approximately 25 to 35 millimeters (1 to 1.5 inches).
Black widow spiders construct irregular, tangled webs that often appear messy. These webs are known for their strength and stickiness. They are commonly found in dark, undisturbed areas, such as woodpiles, sheds, garages, and basements, often near ground level. While males and juveniles exist, they are smaller and often have different markings, making the adult female the primary focus for identification.
Common Black Widow Mimics
Several spider species are frequently mistaken for black widows due to shared dark coloration or body shape. Among the most common are false widow spiders, belonging to the genus Steatoda. These spiders, such as Steatoda grossa (cupboard spider) and Steatoda nobilis (noble false widow), often have dark, sometimes shiny, bodies and globular abdomens, contributing to the confusion.
Many false widow species are dark brown to black, leading to misidentification, especially in low light. Some Steatoda species may also have pale or lighter markings on their abdomen. These markings, while not an hourglass, can be misinterpreted as a variation of the black widow’s distinctive symbol.
Beyond false widows, other dark-colored spiders, similar in size or body shape, may also cause confusion. These might include certain types of orb weavers or funnel weavers that share a dark hue. However, their specific features typically diverge upon closer inspection.
Key Distinctions for Identification
Distinguishing true black widows from their mimics involves observing specific features. The most definitive characteristic of a female black widow is the vibrant red or reddish-orange hourglass marking on the underside of her glossy, jet-black abdomen. In contrast, false widows (genus Steatoda) generally lack this distinct red hourglass.
While some false widows may have pale, white, or cream markings on their abdomen, these are typically not hourglass-shaped and are often located on the top rather than the underside. Subtle differences also exist in body sheen and shape. True black widows have a notably shiny, almost lacquered, black appearance, while many false widows, even if dark, often appear duller or have a brownish-black hue. Although both can have globular abdomens, the black widow’s abdomen is typically very rounded and smooth, often described as spherical. False widows might have slightly less pronounced roundness or a more varied texture on their abdomen.
The webs also offer clues for differentiation. Black widows build a three-dimensional, irregular, and often messy web composed of strong, sticky silk. This web often makes a crackling sound when broken. While false widows also construct irregular, tangled webs, they might not possess the same degree of strength or stickiness as a black widow’s web.