Are Black Widows in Colorado? What to Know and Do

Black widow spiders do live in Colorado, and the species you’re dealing with is the western black widow, Latrodectus hesperus. They’re found across much of the state, especially along the Front Range and the eastern plains, where dry conditions and rocky terrain give them plenty of hiding spots. That said, the actual risk they pose is considerably smaller than most people assume, and knowing a few practical details about their habits, their habitat, and what to do if you’re bitten puts you well ahead of the fear.

Which Black Widow Species Lives in Colorado

The United States is home to three recognized black widow species. The southern black widow (Latrodectus mactans) dominates the Southeast. The northern black widow (Latrodectus variolus) ranges through the eastern states and parts of the Midwest. Colorado falls squarely in the territory of the western black widow, Latrodectus hesperus, which ranges from the Pacific coast through the interior West and into parts of Texas. If someone in Colorado tells you they found a black widow, this is almost certainly the species they’re talking about.

Research on L. hesperus has confirmed that populations across its range are not all identical. Male western black widows can distinguish between webs produced by females from different geographic populations using airborne chemical cues, and laboratory crosses between distant populations sometimes fail to produce viable offspring.¹ In practical terms, that means the black widows in your garage in Colorado Springs are genetically somewhat distinct from those in, say, coastal California, though they look and behave similarly enough that the identification and safety advice is the same.

How to Identify a Western Black Widow

The classic image is accurate for adult females: a shiny, jet-black, globe-shaped body with a red hourglass marking on the underside of the abdomen. That hourglass can range from a clean, connected shape to two separate red triangles, depending on the individual. The female’s body, not including the legs, is roughly the size of a large pea, and with legs extended she spans about the width of a quarter to a half-dollar.

Males and immature spiders are where identification gets tricky. Males are much smaller, with narrower abdomens and longer legs relative to body size. They tend to be brownish or grayish with lighter markings, sometimes including red or orange spots or stripes on the dorsal side of the abdomen. Juveniles of both sexes look similar to males, with mottled brown, tan, and white patterns. Many people overlook immature black widows entirely or mistake them for other cobweb spiders. If you’re finding small brownish spiders in messy, tangled webs in dark corners, it’s worth considering that they could be young black widows even though they lack the classic all-black coloring.

The web itself is another good identifier. Black widows spin irregular, three-dimensional cobwebs rather than the neat, circular orb webs you see stretching between fence posts. The web has a tangled, almost haphazard appearance, with a dense retreat area where the spider hides and sticky “gumfoot” threads that anchor to the ground to snag crawling insects. Research on the architecture of these webs shows that the proportion of sticky capture threads versus structural support threads shifts depending on whether the spider is well fed or hungry, with hungry spiders investing more heavily in the sticky capture elements.²

Where in Colorado You’ll Encounter Them

Western black widows prefer dry, sheltered spots close to the ground. In natural settings across Colorado, that means rock crevices, rodent burrows, fallen logs, and the bases of shrubs, particularly in the grasslands and semi-arid landscapes east of the Rockies. They’re less common at higher elevations and in heavily forested mountain areas, where the climate is cooler and more humid than they prefer. You’re far more likely to find one in Pueblo or on the eastern plains near Burlington than in a mountain town like Breckenridge.

Around homes, the typical hiding spots are garages, sheds, crawl spaces, meter boxes, window wells, stacked firewood, outdoor furniture that doesn’t get moved often, and the undersides of deck railings. Black widows are nocturnal and reclusive, so you’ll rarely see one out in the open during the day. They build webs low, often at ground level, and tend to retreat deep into crevices if disturbed.

Urban areas along the Front Range are particularly hospitable. Research comparing western black widow populations in urban and desert habitats has found that urban settings create measurably warmer nighttime microclimates in and around spider webs, with urban webs running roughly 2 to 5 degrees Celsius warmer than desert webs at night due to the urban heat island effect.³ That extra warmth, especially during spring, can extend the active season and make suburban yards and structures attractive habitat for these spiders.

How Dangerous Is the Venom, Really

Black widow venom gets its punch from a protein called alpha-latrotoxin. When injected through a bite, this toxin targets nerve terminals and triggers a flood of neurotransmitter release. It works by binding to receptors on nerve cells, forming tiny pores in the cell membrane that allow calcium to rush in, which in turn causes the nerve to dump its chemical signals uncontrollably.⁴ The toxin can also activate signaling pathways through a receptor called latrophilin, amplifying the effect.⁵ The result is that muscles contract involuntarily, which is why bites typically produce cramping and pain rather than local tissue damage.

The good news: fatal outcomes are extremely rare. A review of national poison center data covering over a decade of reported black widow exposures across the United States found that the vast majority result in minor consequences, and supportive care is the primary treatment approach.⁶ Deaths in healthy adults are vanishingly uncommon with modern medical care. The people most at risk for serious complications are very young children, elderly adults, and those with significant underlying heart or respiratory conditions.

What a Black Widow Bite Feels Like

The initial bite itself is often described as a sharp pinch, but it can be mild enough that some people don’t notice it at first. What makes a black widow bite distinctive is what follows over the next thirty minutes to a few hours. The venom doesn’t cause dramatic local swelling or tissue destruction the way a brown recluse bite can. Instead, the effects are systemic, spreading through the nervous system.

A clinical review of 163 black widow envenomation cases found that the most common presenting complaints were generalized pain in the abdomen, back, and legs.⁷ The abdominal pain can be severe enough to mimic appendicitis or other surgical emergencies, which sometimes leads to misdiagnosis in emergency rooms. Other common symptoms include muscle rigidity, sweating, elevated blood pressure, nausea, and a general sense of restlessness or anxiety. The severity varies significantly from person to person. Some bites produce only local pain and mild muscle cramps. Others lead to full-body muscle spasms that last for hours.

One pattern worth knowing: if you find two small red puncture marks close together and develop worsening abdominal or back cramps over the following hour, take it seriously even if the bite site itself looks unremarkable. The absence of dramatic local swelling does not mean the venom isn’t circulating.

What to Do If You’re Bitten

If you suspect a black widow bite, clean the area with soap and water, apply a cold compress, and head to an emergency room or urgent care. Try to stay calm and avoid exertion, which can speed circulation of the venom. If you can safely capture or photograph the spider, that helps with identification, but don’t risk another bite to do so.

At the hospital, treatment depends on how severe your symptoms are. Most bites are managed with pain control and monitoring. Opioid painkillers combined with muscle relaxants like benzodiazepines can provide temporary relief, though they don’t neutralize the venom itself. For more serious envenomations, a specific antivenom exists and is the most effective treatment available, with clinical evidence showing it outperforms symptom management alone in terms of pain resolution, reduced need for additional treatment, and shorter hospital stays.⁸ However, antivenom isn’t given to everyone because it carries a small risk of allergic reaction. Your doctor will weigh the severity of your symptoms against that risk.

The vast majority of people recover fully within a few days to a week. Lingering muscle aches and fatigue for a week or two after a bite are common but resolve on their own.

Keeping Black Widows Out of Your Space

You can’t eliminate black widows from the Colorado landscape, and given that they eat pest insects like grasshoppers, beetles, and flies, you wouldn’t necessarily want to. But you can make your home and yard less inviting and reduce the chance of an unpleasant surprise.

• Wear gloves: Any time you’re reaching into dark spaces, firewood piles, meter boxes, window wells, or storage areas that haven’t been disturbed in a while, put on thick leather or heavy work gloves. Most bites happen when someone sticks a bare hand into a spot where a spider is hiding.
• Shake out items: Shoes left in the garage, gardening gloves stored in the shed, camping gear pulled out of storage, and clothing that’s been sitting undisturbed all deserve a good shake before you put them on or reach inside.
• Reduce clutter: Black widows love undisturbed piles of stuff. Stacked boxes, old lumber, rock piles near the foundation, and dense ground-cover plantings right against the house all provide ideal habitat. Moving storage off the ground and keeping the perimeter of your house clear reduces nesting opportunities.
• Seal entry points: Caulk gaps around windows, doors, utility entries, and foundation cracks. Install tight-fitting door sweeps. These steps help keep spiders from moving indoors as temperatures drop in fall.
• Use outdoor lighting strategically: Bright lights near the house attract insects, which attract spiders. Switching to yellow or sodium-vapor bulbs, or moving lights away from doorways to draw insects farther from the house, indirectly reduces spider presence.
• Knock down webs: Regularly sweeping away cobwebs from garages, crawl spaces, and outdoor structures forces spiders to relocate. It’s not a permanent solution on its own, but consistent removal discourages them from establishing in high-traffic areas.

Chemical insecticides can kill individual spiders on contact, and residual sprays applied to cracks and crevices may provide some protection. However, the reclusive habits of black widows mean sprays often miss them entirely. Direct removal by knocking down webs and crushing or relocating spiders you find tends to be more effective around the home than broadcast spraying.

The Fear Versus the Reality

Black widows get outsized attention relative to the actual danger they present. A large international study of media coverage around spider bites found that news reports about spiders are consistently and unnecessarily alarmist, that fewer than one in ten bites described in news stories were plausibly delivered by the species named in the report, and that sensationalized spider stories get shared on social media at higher rates, creating a feedback loop that warps public perception of risk.⁹ The same dynamic applies to black widows in Colorado. Local news segments about “deadly spiders lurking in your backyard” drive fear in a way that’s out of proportion to the actual bite rate and medical outcomes.

The poison center data bear this out: across more than a decade of reported exposures nationwide, the overwhelming majority of black widow encounters result in minor effects.⁶ Black widows are not aggressive spiders. They bite defensively when physically compressed against skin, like when you put on a glove with one inside. They don’t chase people, they don’t seek out human contact, and they’d rather retreat into their messy web than confront something thousands of times their size.

That’s not a reason to be careless. Respect them the way you’d respect a wasp nest: know they’re around, take simple precautions, and don’t handle them. But the level of anxiety many people feel about black widows doesn’t match the evidence about outcomes.

Other Spiders Commonly Mistaken for Black Widows in Colorado

Colorado is home to several dark-bodied spiders that get mistaken for black widows. The false black widow (Steatoda grossa) is probably the most common source of confusion. It’s in the same family (Theridiidae), builds similar messy cobwebs, and has a round, dark-brown to purplish-black abdomen. The key differences are the absence of a bright red hourglass, a generally browner or more matte appearance rather than the true black widow’s high-gloss jet-black finish, and a less prominent or differently shaped marking on the abdomen, often a pale crescent or band rather than a red hourglass. False black widows can bite and cause mild local pain, but their venom is far less potent.

Woodlouse spiders, various ground spiders, and even immature orb weavers get brought to pest control companies by alarmed homeowners convinced they’ve found a black widow. The combination of dark coloring and a round abdomen is enough to trigger the identification in many people’s minds. If you’re genuinely uncertain, a clear photo of the spider’s underside, showing whether an hourglass marking is present, is the fastest route to a definitive answer. County extension offices in Colorado are generally happy to identify spider photos, and several online arachnology communities provide reliable IDs within hours.

Black Widows and Colorado’s Changing Climate

Warming temperatures and expanding urban development along the Front Range are worth watching from a black widow perspective. Research on L. hesperus in urban versus natural habitats has documented that the urban heat island effect creates warmer microclimates in spider web sites, particularly at night and during the spring months.³ These warmer conditions can shift how quickly spiders develop and how long their active season lasts. Extreme heat doesn’t necessarily help them, as very high temperatures slow development, but the moderate warming that urban environments provide in spring and fall likely extends the window during which black widows are active and reproducing.¹⁰

For Colorado residents, this means that encounters with black widows in suburban and urban areas along the Front Range corridor, from Fort Collins through Denver to Colorado Springs and Pueblo, are plausible from roughly late spring through early fall, with peak activity in July and August when nighttime temperatures stay warm. Farther east on the plains, where summers are hot and dry, black widows thrive around farmsteads, outbuildings, and rock piles. Higher-elevation mountain communities remain largely outside their preferred range, though the occasional spider turns up in a warm microhabitat like a heated garage or greenhouse even in mountain towns.