'Black widows are super abundant in Phoenix.' Everything to know about these arachnids

While black widows, known for their potent venom, may seem intimidating, these spiders are typically not aggressive and fatalities from their bites are exceedingly rare. It's important to remember that these spiders play a vital role in our ecosystem by helping control insect populations.

Black widow prevalence can vary depending on the region and conditions, but generally, black widows prefer dry and arid environments, which makes Arizona's climate suitable for their survival.

Black widows are abundant around the Valley, particularly in urban areas where populations can be significantly denser than in the desert. So, it's a good idea to learn more about these eight-legged residents.

Whether you're trying to prevent them or learn more about them, here's everything you should know about black widows in Arizona.

What does a black widow look like?

Black widows are small to medium-sized spiders with shiny black bodies. The females can easily be spotted by their distinctive red or orange hourglass-shaped marking on the underside of their abdomen.

According to the National Geographic website, adult females are larger than males, with a body length of about 1.5 inches, while males are smaller. The males are also not black, but instead brown or grey with small red dots.

Females are far more venomous than males, which are considered relatively harmless.

Where are black widows most common?

Johnson says there isn’t data to get exact numbers on which state has the most black widows. However, they are prevalent in states with warm and dry climates, and some of the states where black widows are most encountered include:

• California
• Arizona
• Texas
• Nevada
• New Mexico
• Utah

How common are black widows in Arizona?

“Black widows are super abundant in Phoenix and in Arizona and in the desert southwest, and really across the western United States,” said Chad Johnson, associate professor in the school of mathematical and natural sciences at Arizona State University West.

“They appear to be most densely populated in urban areas," he said. "We have some old data that suggest their populations can be 20 or 25 times more densely populated in the city than they are in the desert.”

In Phoenix, this boils down to water. Johnson says that if you supplement your lawn, or your neighborhood does, you are likely to have vegetation that attracts things like crickets and cockroaches, which will ultimately attract black widows.

“They are super abundant and disperse, widely through ballooning, and so they can show up just about anywhere. But real bad infestations are almost always about prey, populations, and unattended areas where bushes don't get trimmed and webs don't get knocked back,” said Johnson.

What attracts black widows to your house?

“Black widows are attracted to areas with abundant prey and places to set up their shop to catch their prey. This pretty much boils down to if you have ground-based arthropods like crickets and cockroaches, though they will also take geckos, scorpions,” said Johnson.

Here are some factors that can attract black widows to your house:

• Clutter and debris: Piles of wood, leaves, cardboard boxes and other debris can provide hiding spots for these spiders.
• Outdoor structures: Sheds, garages and outdoor storage areas are attractive to black widows because they provide shelter and are often less disturbed by human activity.
• Light sources: Black widows may set up their webs near light sources, where insects are drawn. This can include outdoor lights, porch lights and windows.
• Landscaping: Overgrown vegetation and bushes close to the house can create hiding spots and attract insects, which, in turn, attract black widows.

How common are black widows in homes?

“Having black widows inside the home is very rare. The few times I've seen it, it stems from them being very abundant outside the home and they are almost accidentally brought inside the house,” said Johnson.

Black widows typically seek out outdoor locations that offer easy access to prey.

“I would certainly never encourage someone to spray inside their house because they want to eliminate black widows unless it's some sort of complete infestation that needs to be holily eradicated,” said Johnson.

What time of year are black widows most active?

Black widows are most active in the spring, summer and early fall. There’s three or four months, our coldest months here in the Valley, where you don’t see many webs.

“But I can still find webs occasionally in February and March of spiders that are just hunkering down and waiting for the weather to warm up in the spring,” said Johnson.

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How toxic are black widows?

Black widow spiders are known for their venomous bites, but the level of toxicity and the effects of their bites can vary. While black widow venom contains potent neurotoxins, these spiders are not inherently aggressive and typically only bite in self-defense when they feel threatened.

“All bites do not inject the same amount of venom. But in terms of the sheer toxicity, we do consider black widow venom to be some of the most dangerous venom to human beings, that's out there,” said Johnson.

The severity of a black widow bite symptoms can depend on several factors, including the individual's sensitivity to the venom, the amount of venom injected and the location of the bite.

Some common symptoms of a black widow bite may include:

• Muscle cramps and spasms.
• Sweating and fever.
• Nausea and vomiting.
• Headache and dizziness.

“The important thing about widow venom is that it appears to be specifically targeted at the mammalian immune system,” said Johnson. “The belief here is that black widows have historically competed with small rodents for burrows in the desert. Natural selection over hundreds and hundreds of generations, thousands of years has yielded black widow venom that is very good at harming mammals, like us.”

What should you do if a black widow bites you?

Johnson mentions that black widow bites are relatively rare, but nothing to mess around with.

“A lot of times people don't know what they were bit by, so it can be hard to know what to do,” said Johnson. “But if you know that you were bit by a decent sized, and therefore female, black widow, most people would recommend going to the emergency room to be monitored.”

He also mentions that reactions to black widow bites are as variable as they are to other environmental allergens. Some people have no response whatsoever while others have a fatal or near fatal response.

“For this reason, everyone should be monitored if they are bitten, and anyone with a compromised immune system, including small children and elderly people, should be particularly careful,” said Johnson.

Does a black widow bite hurt?

“I've had people tell me that it was the most painful thing that they have ever experienced, and I've had people tell me that it was like any spider bite, kind of itchy,” said Johnson. “The immediate pain surrounding it is less important than the reaction it creates in the immune system.”

It all depends on your pain tolerance. Some say it's very painful while others might not feel anything. The pain typically starts at the site of the bite and may then radiate to other parts of the body. It's often described as a sharp, stabbing pain or a burning sensation.

The intensity of the pain can vary from person to person and may depend on factors like the individual's sensitivity to the venom, the location of the bite, and the amount of venom injected.

“I handled tens of thousands of them each year and I've never even really been close to a bite. It's really something that happens when you are either reckless or unaware of their presence,” said Johnson.

While black widow bites are painful and can be uncomfortable, they are rarely life-threatening if promptly treated by a health care professional. If you suspect you've been bitten by a black widow spider, it's essential to seek medical attention to manage the symptoms and receive appropriate care.

When should I be worried about black widows?

Johnson explains that the only reason to be worried about black widows is because of the toxicity of their venom.

“As predators, they are eating a lot of the insects that you might not like to have around,” Johnson said. “I guess their webs can be somewhat unattractive and make people think of untidiness, but there is no other reason to dislike black widows.”

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How can I get rid of black widows?

Johnson recommends leaving them alone unless they are in your home.

But, if you would like to eradicate them outside, Johnson recommends going out at night with a headlamp and knocking the spider out of the middle of the web onto the ground and stepping on it.

“Beware though that threatened spiders emit an incredibly sticky silk, and this can stick to a stick or broom and you end up hitting it and not being able to realize where it has gone, and it has usually adhered to the stick,” said Johnson.

He also mentions that pesticides will knock back the populations of their prey and that may limit the spider’s ability to breed and produce a second generation, but pesticides really don’t do much to the black widow, unless they are sprayed directly on the spider.

“If you’re going to spray directly on the spider, you may as well save yourself the money and just step on the poor thing,” said Johnson.

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