Seen more black widow spiders around Colorado lately? Don’t worry, arachnid expert says.

Black widow spiders are no stranger to Colorado, but does it seem like there are always more around this time of year?

The weather gets cooler and temperatures start dropping below freezing, so it only seems natural spiders and other creepy crawlies that are getting inside are trying to escape the chill.

Residents may even start seeing them more and more and think their house or the city itself might be overrun with the little black spiders with the red hourglass shape on their undersides, but Paula Cushing, a senior curator of invertebrate zoology at the Denver Museum of Nature and Science who specializes in arachnology, said that’s probably not the case.

So, why does it seem more black widows are around and even inside right now?

They’re “just looking for a good time,” Cushing said.

The western black widow, the only widow species native to Colorado and the only spider species that can harm a person with its venom, is entering the reproductive phase of its life cycle, so more are out and about looking for mates.

“At this time of year, what’s oftentimes happening is the males of a lot of different spider species are maturing and getting active, and the black widow females are getting mated and making egg sacs,” Cushing said. “So, there’s a lot more activity in general in black widow populations during this reproductive cycle, so they just might end up being more noticeable.”

A desperate black widow could very well end up somewhere it shouldn’t be on accident while looking for that mate.

But with the humid summer increasing insect populations, could black widows also be on the rise in the state?

Some spider populations could see an increase, but Cushing said that’s probably not happening with black widows.

Western black widows do best in dry climates, and she has not seen any papers or research about humid seasons improving black widow populations.

Black widow populations are pretty healthy at this time every year.

With the boom in black widow activity, it is good to stay vigilant about some contact with black widows, but Cushing said it’s actually pretty rare for them to try and bite a human.

“Black widows don’t like to waste their metabolically expensive venom on something they can’t eat,” she said. “They can’t eat a human, so bites are really, really rare.”

Bites that do occur could come from someone moving a flower pot or some furniture and hitting one. The spider is just trying to protect itself from getting squished, and it would rather run away than waste time biting a person.

The Colorado State University Extension concurs with Cushing, and further states in a fact sheet that black widows rarely ever bite when not in a web.

Male widows, the ones wandering trying to find mates, are even less likely to hurt a person.

“Being smaller than the females, they have smaller venom glands and smaller fangs,” Whitney Cranshaw, professor emeritus at CSU, stated in the factsheet. “Thus, it is unlikely that males, even if encountered, could penetrate the skin of an adult human.”

Widow spiders have to be provoked in a highly specific manner in order to induce them to bite a human, Cranshaw stated.

Cushing also said a lot of black widow bites could be asymptomatic, as the spider might bite without injecting venom.

The CSU factsheet offers several tips to monitor for symptoms of a venomous bite.

A slight swelling and redness may develop at the bite site, and muscle and chest pain or tightness is the most common reaction to the toxin.

The pain may also spread to the abdomen, producing stomach cramping and nausea, according to the factsheet.

Other general symptoms include restlessness, anxiety, breathing and speech difficulty, and sweating.

Often there is a general sense of discomfort shortly after the bite, and acute symptoms increase in severity during the first day. Symptoms usually decline after 2 to 3 days but some may continue for several weeks or up to a month after the bite.

In general, though, Cushing said black widows do more good for Colorado than bad, and it’s best to leave them alone if they’re found outside.

“Spiders are incredibly important to controlling insect populations,” Cushing said. “Spiders are the good guys and gals of the world of arthropods. They’re major predators and have fascinating life cycles. They’re helping you, not hurting you.”

Editor’s note: This article was updated at 5:35 p.m. Friday, Nov. 17, 2023, to correct that the red hourglass shape is on black widow spider’s abdomens.