The Latrodectus genus is all under the family Theridiidae. It is a large family of spiders, also known as the tangle-web spiders, cobweb spiders and comb-footed spiders. The diverse family includes over 2200 species in over 100 genera).
The origin of the brown widow is uncertain as specimens have been independently discovered in both Africa and the Americas. In the US, they can be found in the southern half of the country. Other countries such as Australia, Afghanistan, Japan, Tanzania, South Africa and Cyprus have reported also presence of the arachnid.
The spider is lighter in color than the black widow. It ranges from tan to dark brown to black. Like the black widow, it also has an "hourglass" marking on the underside of the abdomen that is a vivid orange or a yellowish color.
The brown widow also has a black-and-white geometric pattern on the dorsal side of its abdomen. The Latin name comes from this pattern but the pattern can become obscured when the spider's coloring darkens over time.
Are brown widows displacing black widow spiders around southern California homes?
Brown widow spiders are relatively new to North America, where they were first documented in Florida in 1935, and even newer to southern California, where they were only recently discovered in 2003. However, in the last decade they have been so successful that they may be displacing native black widow spiders. If so, the overall danger to homeowners may decrease because brown widow spider bites are less toxic than those of native western black widow spiders.
In "The Prevalence of Brown Widow and Black Widow Spiders (Araneae: Theridiidae) in Urban Southern California," an article in the July issue of the Journal of Medical Entomology, the authors describe the results of their efforts to document the presence of brown widows in southern California by performing timed searches in various habitats, such as urban properties, agricultural lands, developed parks, and undeveloped natural areas. They also included the native western black widow spider to compare the abundance and habitat selection of the two species.
