Summer’s Uninvited Visitors: What to Know About Black Widow Spiders

This is the time of year when we may come upon increased numbers of black widow spiders in and around our homes.

Although there are several species found in temperate regions around the world, black widows are usually identified by the colored, hourglass-shaped mark on their abdomens. They are active when the temperature is 70 degrees or higher, but they can survive lower temperatures with the right conditions. They spin irregular webs, which they build at night near ground level, and are found where there are food sources and protective environments. Black widows are solitary spiders and prefer dark, secluded areas like crevices, woodpiles, sheds, garages, dark corners, basements, under rocks, closets, and cluttered areas.

Contrary to their creepy, ominous appearance and what you may have seen in the Arachnid horror flick, these shy creatures are not lying in wait to attack you. In fact, they would rather be left alone and will run and hide given the chance.

But they will bite in self-defense, such as when someone accidentally grabs or sits on them. In the United States, there are actually three species of widow spiders that are venomous to both pets and people: the Western black widow, found in the western regions of the country; the Northern black widow, found in the northernmost areas of the states and southeast Canada; and the Southern black widow, found in the southeast United States from Florida to New York and some southwest states. Black widow spiders are found in every state but Alaska.

This spider’s bite is feared because its venom is reported to be 15 times stronger than a rattlesnake’s, according to National Geographic. In humans, bites produce muscle aches, nausea, and a paralysis of the diaphragm that can make breathing difficult. However, while a healthy adult will not likely suffer serious damage or death, bites can be fatal to small children, the elderly, or the infirm. Fortunately, fatalities are fairly rare.

Your pet can be bitten by a black widow indoors or outside. Younger and older pets are at increased risk of fatal complications from a black widow bite. A dog or cat bitten by a black widow spider must be treated with anti-venom, supportive therapy, and other medications as necessary.

Preventative measures can help keep black widow spiders from moving into your yard and home.

  • Remove material such as junk or wood piles where they might hide and always check firewood for stowaway spiders before bringing it into the house.
  • Eliminate clutter in storage areas such as basements, attics, and closets.
  • Keep plants and grass trimmed near your house and remove clutter and debris from around your home’s perimeter.
  • Fix cracks in your home’s foundation, seal openings, and install screens and door sweeps to help prevent spider entry.

When spider webs are visible, use caution before putting your hands or feet in that area. You should also wear heavy gloves when moving items that have been stored for a long period of time and shake out shoes before wearing them. Outdoors, store firewood at least twenty feet from the home and five inches off the ground. If you suspect a spider infestation, contact a black widow control specialist immediately. This is the safest way to get rid of black widow spiders in the home.

Do-it-yourself pest control applications from your local home improvement store can help prevent and/or kill black widows, or you can call in a professional. The California Structural Pest Control Board licenses and regulates pest control companies, pest management professionals, fumigators and structural pesticide applicators. To verify a license, visit and click on the “License Search” button.

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