The most common spiders around Denver homes include wolf spiders, funnel web grass spiders, yellow sac spiders, cellar spiders, and the western black widow. Most are harmless, except for the black widow, which is dangerous if it bites you.
Finding a spider in your garage or along your foundation is unnerving even when it's harmless. Knowing which species are common in the Denver area, and which ones are dangerous, can help you make better decisions about what to do when you see one.
Wolf spiders are large, fast, and probably the most startling spiders you'll encounter. They don't build webs. Instead, they hunt on the ground, which means they sometimes wander into garages and basements. They can bite if handled, but the bite is comparable to a bee sting. They're not dangerous, despite being startling to watch.
Funnel web grass spiders are the ones building sheet-like webs with a funnel retreat in your lawn, shrubs, and window wells. They're extremely common in the Denver area and completely harmless to people. The webs are more of a nuisance than the spider itself.
Indoors, you might run into yellow sac spiders. These small, pale spiders tend to weave little silk sacs in tight corners or along ceilings. They account for a significant number of indoor spider bites, which typically happen by accident when someone puts on clothing where a spider is hiding or rolls onto one in bed. Fortunately, while the bite might cause some mild redness and irritation, it isn't medically dangerous.
Cellar spiders (often called daddy longlegs) are also common to the area. These thin, long-legged spiders prefer quiet, dark spaces like basements, garages, and crawl spaces. Not only are they completely harmless to us, but they are actually quite beneficial, as they actively hunt and eat other insects and spiders.
The western black widow is the one to take seriously. Females are glossy black with a red hourglass marking on the underside. They like to be in dark and undisturbed places. Some common places you’ll find them: woodpiles, rock walls, meter boxes, storage sheds, and the undersides of outdoor furniture. Their bite is dangerous, and you need medical attention if you are bitten. But you should also know that fatalities are extremely rare. If you see one, give it space and consider having the area treated.
One spider people often ask about is the brown recluse. It is not established in Colorado. Occasional specimens arrive via shipping or moving boxes, but there is no resident population in the Denver metro area.
If spiders or other pests are a concern around your Denver property, Mosquito Squad of West Denver can help. A technician can come to your property and find out where spiders and other pests hide. Then they can treat your home and yard accordingly to help reduce the population on your property.
