Which Widow Spider Species Are Commonly Found Within Homes In Southern California? Are They All Dangerous?

Black widow spiders are notorious for their painful and potentially life-threatening bites, but most experts will tell you that these spiders are shy around humans and do not infest homes often. However, it is important to note that several widow spiders have been documented, and not all species behave in the same manner. Many people assume that the “black widow” is just one single spider species, but there exists multiple black widow species, including the western, northern and southern black widow species. In southern California, only one “black widow” spider species can be found, but another “widow” spider species, the “brown widow,” has been invading the region for the past several years.

The western black widow is the most abundant widow spider in southern California, and this species is often found near, and even within homes in Ventura County. The brown widow has been increasing its habitat range and population size in southern California, and researchers now know that this invading species is quickly displacing the native western black widow. Unfortunately, the brown widow, much like the western black widow, is able to transmit highly toxic venom into a person’s bloodstream with their painful bites. Although the brown widow can inflict medically significant bites, the western black widow is considered the most dangerous spider species in all west coast states.

The western black widow and the brown widow species both look quite similar and each species is known for its tattered cobwebs and reclusive habitat. While the western black widow is a shy and reclusive species, they are often found along the foundation of homes due to their preference for establishing shelter in cracks, crevices, trash piles and cluttered conditions. Their habitat preference explains why they are particularly common within closets, storage areas, rock-walls, barns, sheds, around patio furniture and garages. It is not uncommon to find numerous female black widows within inches of one another in these particular conditions. The brown widow also dwells within these conditions, but unlike the western black widow, they are not often found within garages, closets and sheds. The brown widow is brown to dark-brown in color, while the western black widow has a red hourglass shape on the underside of its abdomen and is often black in color. Both of these species are relatively easy to recognize for pest control professionals.

Have you ever found a widow spider species around your home?