The brown widow spider, Latrodectus geometricus, is a relative of the more infamous black widow. Originally from Africa or South America, this species has spread to many warmer regions, including the southern and western United States, leading to more frequent contact with people. This spider belongs to the same genus, Latrodectus, a group known for potent venom.
Identifying a Brown Widow
The most reliable way to identify a brown widow is by its unique egg sac. The female produces a tan, spherical sac covered in distinctive spiky silk projections, often compared to a sandspur. This is a definitive sign of the brown widow’s presence, and a single female can produce 20 or more sacs in her lifetime. In contrast, the egg sacs of black widows are smooth and pear-shaped.
Visually, the brown widow can be challenging to identify due to its variable coloring. Its body is a mottling of tan, brown, and grey, though some individuals can be dark enough to be mistaken for black widows. The legs feature distinct dark bands at the joints. Mature females often display a geometric pattern on the top of their abdomen.
Like other widow spiders, the brown widow has an hourglass-shaped marking on the underside of its abdomen. However, instead of the bright red associated with black widows, the brown widow’s hourglass is a shade of orange or yellow. Female brown widows have a body length of about 12-16 mm, while males are significantly smaller, at around 6-8 mm.
Habitat and Geographic Distribution
The brown widow is believed to have originated in Africa and has since become established in many subtropical and tropical climates. In the United States, it was found primarily in Florida but has expanded its range significantly. It is now commonly found across the Gulf Coast states, into South Carolina, and throughout the southern and western states, including California.
This spider thrives in human-altered environments, building messy, three-dimensional webs in secluded, cluttered spaces. Common habitats include areas under outdoor patio furniture, inside buckets or planters, among woodpiles, and beneath the eaves of buildings. They are often found in more open locations than black widows, which prefer darker retreats.
The webs are irregular and tangled, with a small retreat where the spider can hide. They are frequently built near the ground in places that offer protection. The spider’s ability to adapt to urban and suburban landscapes has contributed to its successful spread.
Medical Significance of a Bite
Brown widow spiders are timid and will avoid human interaction. They typically only bite when provoked or accidentally pressed against a person’s skin. Their defensive response when disturbed is often to drop to the ground and curl into a ball, feigning death. Males and immature brown widows are not considered a threat due to their small size.
Although the venom of a brown widow is potent, the medical outcomes of a bite are much less severe. This is because the brown widow injects a very small amount of its neurotoxin during a bite. As a result, the severe symptoms associated with black widow envenomation are very rare.
The reaction to a brown widow bite is localized pain and redness at the site. Some individuals may experience cramping or nausea, but these symptoms are mild. An African study of 15 confirmed brown widow bites showed that victims did not develop the severe symptoms seen with other widow species. The bite of a brown widow is not considered dangerous.
Managing Brown Widows Around the Home
Controlling brown widow populations around a home focuses on prevention and physical removal. Reducing clutter in outdoor areas is the most effective strategy, as this eliminates the secluded spaces spiders prefer. You can also:
- Regularly clean and inspect outdoor furniture, stored items, and children’s toys.
- Seal any cracks or openings in a home’s foundation to limit entry points.
- Physically crush or destroy spiders and their spiky egg sacs when found.
- Use a vacuum cleaner to remove spiders, webs, and egg sacs, sealing the bag before disposal.
When brown widows are found, direct removal is a straightforward approach. For more persistent issues, contact insecticides can be applied directly to the spiders and their webs.