Both the redback spider and the black widow spiders belong to the Lactrodectus spider genus. They have red markings and spherical abdomens as well. Despite these simple similarities, the spider are completely different. Once you understand the differences between these two spiders from the widow family, you won't mistake a redback for a black widow again.
The redback spider does share the red marking trait with the black widow spider, but those marking are distinct for both species. The black widow spider is very well known for the hourglass-shaped red marking on the abdomen of female spiders. The mark is quite clear, although the color tone may range from a orange-red to a bright red. The redback spider does have a red mark, but it is a simple vertical line that bisects the abdomen. The color tone of the mark on the redback spider may range from yellowish-red to bright red, but the mark is clearly a line and nothing more. Some females may have a broken hourglass on the underside of their abdomen. The shape loosely resembles that of the black widow spider.
There are significant differences between the genders of the spiders as well. Female and male black widow spider are black, while the redback females may be more of a brown color. The redback males are usually light brown. The males of both species have white markings on their backs. However, the black widow male's markings are lines that radiate horizontally from the center of the abdomen. Redback males have white spots or lines surrounding the faint brown hourglass on their back.
Where to Find Them
True black widow spiders are found throughout the North American continent. They live in crawl spaces, basements and outside in woodpiles and the hollows of trees. A redback spider, however, prefers urban environments that get heavy traffic and attract other insects. Black widows are more solitary spiders.
Scientists once considered the redback spider as a subspecies of black widow spiders. Over the years, the spider's habitats, physical traits and other characteristics have distinguished the two spiders as separate species. The bites of both spiders also are venomous and very painful. However, the first signs of a redback spider bite is a ferocious itching, while black spider bites are first detected by an excruciating pain at the bite site.