Black Widow spiders, belonging to the genus Latrodectus, are highly recognized arachnids across the United States. Understanding where these spiders live and how to properly identify them is important for general awareness. Three primary species are native to the US, and each occupies a distinct, yet sometimes overlapping, area. This overview focuses on defining their physical traits and mapping their presence across the continent.
Identifying US Black Widow Species
Three species of Black Widow spiders are commonly recognized across North America: the Southern Black Widow (Latrodectus mactans), the Western Black Widow (Latrodectus hesperus), and the Northern Black Widow (Latrodectus variolus). The mature female of each species is generally shiny black with a large, globular abdomen. Adult females are significantly larger than males, measuring approximately 0.5 inches in body length.
The Southern Black Widow is characterized by a complete, distinct hourglass marking on the underside (ventral side) of its abdomen, which is typically a vibrant red or orange-red color. The Western Black Widow also features an hourglass marking on the ventral side of the abdomen, though this marking can occasionally be yellow or white. The Northern Black Widow often presents the most variation, as its ventral hourglass marking is frequently broken into two separate triangular or rectangular red spots. The Northern species sometimes retains a row of small red spots along the top (dorsal side) of the abdomen.
Geographical Distribution Across the United States
The presence of the three Black Widow species can be largely segmented by major geographical regions, though their ranges do overlap in certain areas. The Southern Black Widow (L. mactans) is primarily found throughout the southeastern states, extending as far north as Ohio and west into Texas, Oklahoma, and Kansas. This species thrives in the warmer, often more humid climates characteristic of the Southeast.
Conversely, the Western Black Widow (L. hesperus) dominates the western half of the continent, with a range that stretches from the Pacific Coast eastward to the Rocky Mountains and into the western portions of the Great Plains. This species is particularly common in the four deserts of the American Southwest. The boundary between the Southern and Western species is generally considered to be the Rocky Mountains.
The Northern Black Widow (L. variolus) generally inhabits the Middle Atlantic states, including New Jersey, Delaware, and Maryland. It extends north along the Eastern Seaboard into New England, overlapping considerably with the Southern species.
Preferred Habitats and Hiding Spots
Black Widows seek out specific micro-environments to establish their irregular, tangled cobwebs. These spiders are attracted to dark, secluded, and undisturbed spaces that offer protection from the elements and predators. This preference means their webs are typically built close to the ground in areas with minimal human traffic.
Common outdoor habitats include woodpiles, stacks of lumber, under stones, and inside hollow logs or rodent burrows. Human-made structures also provide ideal shelter, with webs frequently found beneath outdoor furniture, inside utility boxes, or tucked into the dark corners of sheds and garages. The messy, disorganized structure of their web is a key indicator of their presence.
When Black Widows move indoors, they gravitate toward areas that mimic their preferred outdoor conditions: darkness and minimal disturbance. Basements, crawl spaces, and attics are common indoor locales, especially if they are cluttered with stored items that provide many small crevices for shelter.
Distinguishing Black Widows from Lookalikes
The most frequently confused species is the False Black Widow (Steatoda grossa), which shares the globular body shape and dark, glossy coloration of the true Black Widow. A primary distinguishing feature is the absence of the prominent, bright red hourglass marking on the underside of the False Black Widow’s abdomen.
False Widows are typically chocolate brown or purplish-brown and may have subtle, light-colored markings on the top of the abdomen. Another related species, the Brown Widow (Latrodectus geometricus), does have an hourglass, but it is typically a dull yellow or orange color and less distinct than the red marking of the Black Widow. The Brown Widow can also be identified by its unique egg sac, which is spherical and covered in small, spiky tufts, unlike the smooth, pear-shaped sac of the Black Widow.