Black widow spiders are among the most recognized arachnids, often sparking curiosity and sometimes apprehension due to their distinctive appearance. A common question arises about a specific red marking on their bodies. Understanding this feature and other characteristics helps in accurate identification of these spiders.
The Distinctive Red Marking
Adult female black widow spiders possess a bright red marking on their underside. This marking is most frequently seen as an hourglass shape, located on the underside of their abdomen. Its color ranges from vibrant red to darker shades, or even yellow. Variations exist, including markings that appear as two separate triangles or a broken hourglass shape. This marking serves as a warning signal to potential predators.
Other Identifying Features
Beyond the red marking, female black widow spiders exhibit several other recognizable physical traits. Their bodies are shiny and jet black. Females are larger than males, reaching up to 13 mm in body length, and have a rounded, globular abdomen. Their webs are distinctive, often appearing irregular and tangled yet are structurally strong and sticky. These webs are frequently found near ground level, in secluded, dark areas such as woodpiles or cluttered spaces.
Species and Regional Variations
The genus Latrodectus encompasses several species commonly referred to as widow spiders, and their markings can vary significantly. In North America, species like the southern black widow (Latrodectus mactans), western black widow (Latrodectus hesperus), and northern black widow (Latrodectus variolus) are found. The southern and western black widows generally have a complete red hourglass, while the northern black widow might have a broken hourglass or even a row of red spots on its dorsal side. Brown widow spiders (Latrodectus geometricus), another relative, typically have an orange-red hourglass marking and lighter brown bodies. Males and juveniles display different markings than adult females; males are smaller with red and white stripes or spots, or yellow or white hourglasses, while spiderlings are lighter (orange, brown, or white) and darken with molts.
Importance of Accurate Identification
Understanding how to identify black widow spiders is important for exercising caution. While these spiders are generally reclusive and will typically flee when disturbed, females may bite defensively if they feel threatened or are guarding an egg sac. The bite of an adult female black widow can be medically significant due to its neurotoxic venom, which can cause symptoms such as severe muscle pain, cramping, nausea, and sweating. Although fatalities are rare, particularly with prompt medical care, knowing how to identify these spiders helps in taking appropriate precautions and seeking medical attention if a bite is suspected. When encountering a suspected black widow, it is advisable to avoid direct contact and consider professional assistance for removal if necessary.