Black widow spiders are widely recognized, often prompting questions about their size. Many wonder if these spiders are truly small, given their reputation. Understanding their actual dimensions and distinguishing features helps demystify these arachnids.
The Truth About Their Size
Adult female black widow spiders measure 8 to 13 millimeters (0.3 to 0.5 inches) in body length. With leg span, females can reach 25 to 38 millimeters (1 to 1.5 inches). Their abdomen appears spherical and plump. This size is comparable to a large pea or a small grape, surprising those who expect them to be microscopic or much larger.
Male black widow spiders are considerably smaller than females, about half their size. Their body length ranges from 3 to 6 millimeters (0.12 to 0.24 inches). Males also possess proportionally longer legs compared to their body size. While females are the larger and more commonly observed sex, neither are considered “tiny.”
Beyond Size: Key Identification Marks
Beyond their size, distinct markings help identify black widow spiders. Adult females are glossy black with a red or orange hourglass marking on the underside of their abdomen. This iconic hourglass can vary, sometimes appearing as two separate triangles, dots, or being faded. Some species may also display red spots or stripes on the top side of their abdomen.
Male black widows, in contrast, exhibit different coloration and markings. They are brown or gray, sometimes with lighter patterns, and may have red, orange, or yellow spots or stripes on their abdomen. Any hourglass marking on males is yellow or orange and less pronounced than on females. Both sexes have long, slender legs, with males having proportionally longer ones than females.
Preferred Habitats and Behavior
Black widow spiders inhabit dark, secluded, and undisturbed environments. They thrive in warmer climates across North America. Outdoors, locations include under rocks, in woodpiles, sheds, garages, hollow logs, and areas with debris.
Indoors, they seek out basements, crawl spaces, attics, and other dimly lit, cluttered areas. Black widows construct irregular, tangled, and sticky webs, close to the ground. They are shy and nocturnal, hanging upside down in their web, which makes their hourglass marking visible. These spiders bite only when threatened, particularly if their web or egg sac is disturbed.