Black widow spiders are arachnids often recognized by a distinctive red marking. This common perception does not always reflect their true appearance. Accurate identification of these venomous spiders is important for safety, as their bites can cause severe reactions.
The Iconic Red Mark
The classic red hourglass marking is a widely recognized feature of female black widow spiders. This bright red symbol typically appears on the underside of their shiny, globular abdomen. Its striking color and placement serve as a warning to predators. While iconic and frequently depicted, it is primarily present on adult female black widows.
Beyond the Red: Other Markings and Colors
Not all black widows possess the classic red hourglass, and their markings can vary significantly. Some adult female black widow spiders may have red markings that are not hourglass-shaped, appearing as two separate triangles, two spots, or a broken hourglass. Some adult females might have no red marking at all. Beyond red, markings can sometimes be orange, yellow, or white.
Body coloration varies within the Latrodectus genus. While many adult females are shiny black, species like the brown widow (Latrodectus geometricus) are tan or dark brown with an orange or yellow hourglass. Immature black widows often display a lighter coloration, appearing orange, white, or yellowish, and gradually darken with molts. Male black widows are typically smaller than females and often exhibit more varied patterns, such as red and white stripes or spots on their upper abdomen, and may have less distinct or absent markings.
Identifying Black Widows Without Red
Since the red marking is not universally present, other physical and behavioral traits are useful for identifying black widow spiders. Female black widows generally have a distinctive shiny, globular abdomen and slender legs. Adult females are larger than males, with body lengths typically ranging from 3 to 13 millimeters, and including their legs, they can measure up to 38 millimeters.
Black widows construct irregular, tangled webs, often found near ground level in dark, undisturbed locations. They are nocturnal and are frequently observed hanging upside down in their webs, which can expose any ventral markings. Another characteristic is the presence of a “comb foot,” a row of strong, curved bristles on their hind legs used to wrap prey in silk.
Species Diversity and Regional Variations
The term “black widow” is a common name encompassing several species within the Latrodectus genus, which contains 34 recognized species. This genus includes various “widow spiders” found across different continents. In North America, common species include the Southern black widow (Latrodectus mactans), Western black widow (Latrodectus hesperus), and Northern black widow (Latrodectus variolus), as well as the brown widow (Latrodectus geometricus) and red widow (Latrodectus bishopi).
The appearance of these spiders, including their markings and coloration, can vary significantly depending on the specific species and their geographic region. For instance, the Northern black widow may sometimes lack the hourglass, while the Southern black widow typically has a complete hourglass. These species-specific differences contribute to the wide range of appearances observed in black widow spiders.