Brown Widow Spiders: What to Know

Medically Reviewed by Jabeen Begum, MD on January 16, 2023
Written by Lauren Barrow
6 min read

It seems everyone has heard of the black widow spider. But there is a little-known cousin that's becoming a pest in certain parts of the United States — the brown widow spider (Latrodectus geometricus), also known as the gray widow or brown button spider.

Each season, female brown widow spiders lay several egg sacs, each with 120 to 150 eggs. The egg sacs are distinctive, with silky spikes projecting from the surface, much like a thistle. 

Young spiders called spiderlings hatch from the eggs in 14 to 21 days but stay hidden in the egg sac for a few days to a month. Once they emerge, some stay in the area and may eat a few of their siblings. Many of the remaining spiderlings will spread to nearby areas by ballooning, or using their webs to sail through the air.

After reaching adulthood, the brown widow spiders mate. The female will often kill the male — a common practice among widow spiders, and how they got their name. Male brown widow spiders live for six months to a year. Female brown widow spiders live for up to three years and produce about 5,000 young each season.

Brown widow spiders vary widely in their colors, from very light to very dark, but are not shiny like black widow spiders. Their coloring is mottled, and females have black accent stripes. There is an hourglass shape on the abdomen, usually in a shade of orange. 

Female brown widow spiders are relatively small at about 13 millimeters. The males are about half the size of the females.

The brown widow spider belongs to the Latrodectus genus of spiders, which are known as the true widow spiders. There are several species of widow spiders in the United States, including the northern and southern black widow and the red widow. The brown widow spider is considered one of the least dangerous.

There are other, similar types of spiders not belonging to the same genus, such as the noble false widow and the false black widow.

The brown widow spider is thought to come from either South America or Africa, but no one knows for sure. The brown widow has spread to many other parts of the world, including parts of Australia, Japan, and the Caribbean. 

Brown widow spiders are not native to the United States and are considered invasive. However, they're very common in Florida and are becoming more common in the southern states of the U.S., especially Texas, and now appear to be spreading north through California. 

Brown widow spiders like to live in secluded, woody vegetation and branches just outside of urban areas. They especially like dark places, like empty pots, garages, woodpiles, patio furniture, and abandoned cars. Though the habitats of the brown and black widow spiders overlap, the brown widow appears to prefer more exposed places.

Brown widow spiders feed on insects or just about whatever they can catch in their webs.

Each brown widow spider has six spinnerets that spin silk to make irregularly shaped webs. Sticky droplets on the webs catch their prey. The spider then casts sticky silk to trap them and injects them with venom before eating them.

The most common indicator of spiders is the presence of spider webs, but it's difficult to identify brown widow spiders from the webs alone. You may see the brown widow spiders themselves, although they closely resemble immature black widows, which are much more dangerous. 

The best way to know for sure if you have brown widow spiders and not some other kind of spider is to look for a distinctive spiky egg sac. Other spider species lay smooth, round egg sacs.

The habitat of the brown widow spider has expanded to much of the southwestern U.S. and appears to be growing. Keep your eyes peeled if you live in that region.

Brown widow spiders will live wherever they have the opportunity. Their favorite hiding places are outside, such as in mailboxes, woodpiles, garage junk, and patio furniture, so the best way to prevent brown widow spiders is to get rid of those hiding places.

It is important to try to prevent spider bites as best you can:

  • Don't go outside without shoes.
  • Don’t put your hands in holes or dark places you can’t inspect first.
  • Shake out shoes, gloves, and towels before using them.

Brown widow spiders are venomous, but they're considered much less dangerous than the black widow. Although brown widow venom is just as toxic, the brown widow spider injects a much smaller amount of it. Also, only the adult female brown widow spiders bite. Immature and male brown widow spiders don't bite at all.

Brown widows are much less aggressive than black widows — they prefer to play dead rather than bite and they don't defend their webs. 

Some experts believe that the less dangerous brown widow spiders may eventually displace black widows, especially in urban areas. If so, this may actually result in fewer reports of toxic spider bites.

In some cases, a person who's bitten by a brown widow spider may not even realize it, or they may think it was another kind of bug bite. In many cases, the bite may hurt at first and leave a red spot, similar to the bites of other types of house spiders. About 15% of brown widow spider bites are dry, which means they contained no venom.

There have been a few reports of brown widow spider bite victims needing to go to the hospital. Severe cases are rare, but symptoms include:

  • Muscle pain and cramps
  • Weakness in legs
  • Fever
  • Enlarged lymph nodes
  • Nausea and vomiting

Medical treatment usually isn't necessary for brown widow bites. It's recommended to wash the area with soapy water and use ice to numb the area if it stings.

More severe bites may need treatment by a medical professional. Black widow antivenom (also called antivenin) has been reported to work for brown widow bites.

The bite of any spider has the potential to be dangerous. The following people should seek emergency care after a spider bite:

  • Children, older adults, and people with cardiovascular problems
  • Anyone showing other symptoms, such as severe abdominal pain, a growing wound at the bite site, or difficulty breathing
  • Anyone who has reason to believe they were bitten by a widow or brown recluse — another common type of poisonous spider

Getting rid of brown widow spiders is similar to getting rid of other spiders. Here are some ways to make brown widow spiders go away:

  • Remove clutter and places they like to hide and make webs.
  • Carefully inspect old gloves and shoes left outside. 
  • Seal any cracks in foundations, windows, and doorways.
  • Vacuum and sweep corners, doorways, storage areas, basements, and garages.
  • Make sure you aren’t bringing them in accidentally on wood piles or other things left outside.
  • Sweep down any webs you see.
  • Commercial insecticides can be effective if sprayed into holes and dark crevices, but always read the instructions carefully to make sure you use them safely.

Brown widow spiders are an important part of the ecosystem, though they are technically an invasive species. They're also fascinating and probably less dangerous than they seem, but they should still be taken seriously.