Black widow spiders are among the most recognized arachnids, largely due to their potent venom and characteristic appearance. Their features reveal nuances that help distinguish them from other spider species. This prompts a need for accurate identification and understanding of variations in their markings.
White Markings on Black Widows
Black widow spiders can indeed display white markings, though these are typically not present on adult female black widows. These lighter patterns appear under specific circumstances, often indicating the spider’s age or sex, or distinguishing certain species within the Latrodectus genus. Juvenile black widows frequently exhibit varied coloration, including shades of orange, white, and gray, often with pale stripes or banded patterns on their abdomen. As they mature, these initial markings typically fade, and the spider’s body darkens to the well-known glossy black.
Male black widows, which are considerably smaller than females, also commonly feature white or yellowish markings. These can manifest as stripes or spots on the top of their abdomen. In some species, such as the Western black widow (Latrodectus hesperus), the hourglass marking on the underside of the abdomen, while typically red, can occasionally be yellow or even white. Related species, like the brown widow (Latrodectus geometricus), often have white spots and marginal white stripes on their abdomen, alongside an orange or yellow hourglass.
Key Identification Features
Identifying a true black widow, especially an adult female, relies on several consistent characteristics. The most prominent and widely recognized feature is the bright red or orange-red hourglass-shaped marking located on the underside of its globular abdomen. While this marking is distinctive, its appearance can vary; it might sometimes present as two separate triangles or spots, or be somewhat faded.
The overall body of an adult female black widow is typically a shiny, jet-black. Their body size, excluding legs, usually ranges from approximately 8 to 16 millimeters (about 0.3 to 0.6 inches) for females. The spider also possesses long, slender legs, and some species have a specialized “comb foot” used for flinging silk over ensnared prey. Black widows construct irregular, tangled, and sticky webs, often found in dark, undisturbed areas.
Common Look-Alikes
Several spider species are frequently mistaken for black widows due to similar body shapes or dark coloration, but lack definitive identification markers. False black widows, belonging to the genus Steatoda, are common look-alikes. These spiders often have dark, rounded bodies, but they do not possess the iconic red hourglass marking found on true black widows. Their abdomen shape is typically less perfectly spherical than that of a black widow, and their bites are considerably less dangerous to humans.
Another group often confused with black widows are brown widows (Latrodectus geometricus), which are closely related but distinct. Brown widows vary in color from tan to dark brown, often with mottled patterns on their bodies. While they also have an hourglass marking on their underside, its color is typically orange or yellow, distinguishing it from the true black widow’s red emblem. Their egg sacs also provide a clear distinction, as brown widows produce spiky, tufted egg sacs, unlike the smooth sacs of black widows.