Colorado is home to several orb weaver species, and they’re all harmless. These are the large, round-web spiders you’ll notice on porches, windows, and garden shrubs starting in late summer, growing impressively plump by fall. The two most common are the cat-faced spider and the banded garden spider, both of which look far more intimidating than they actually are.
The Cat-Faced Spider
The cat-faced spider (sometimes called the monkeyface spider) is the most common orb weaver in Colorado. It gets its name from two protruding bumps on its back that resemble cat ears. Females are the ones you’ll actually see: brownish, round-bodied, and up to about an inch in diameter. Males are significantly smaller and rarely noticed.
These spiders build their webs on the sides of buildings, especially around windows and porch lights where insects gather at night. They drop an egg sac in the fall, which means they reach their largest size right around Halloween. Colorado State University runs an annual contest for the biggest cat-faced spider submission, and the record holder weighed in at 3.75 grams, roughly the weight of a penny. If you’ve spotted a chunky brown spider hanging in a circular web near your outdoor lights in September or October, this is almost certainly what you’re looking at.
The Banded Garden Spider
The banded garden spider is the largest and most visually striking orb weaver in Colorado. Females have a silvery body with bold dark and yellow stripes, making them easy to identify. They show up in late summer and early fall in gardens and shrubbery, where they spin highly symmetrical circular webs that can be a foot or more across. Males, as with the cat-faced spider, are much smaller and rarely seen.
You might also encounter other Araneus species around Colorado. These tend to be brownish with large, dimpled abdomens and are sometimes called barn spiders or garden spiders. They build geometric webs among vegetation, fences, and outdoor structures. All of them are harmless.
How to Identify an Orb Weaver
The easiest way to identify any orb weaver isn’t actually the spider itself. It’s the web. Orb weavers are the classic wheel-shaped web builders: a circular frame with radiating spokes and a spiral of sticky silk filling the center. If the web is round and symmetrical, suspended in an open-air space between two anchor points, you’re looking at an orb weaver’s work. The spider typically sits in the center of the web or hides in a nearby corner, connected to the web by a signal line that vibrates when prey lands.
Building one of these webs takes about an hour. Some orb weaver species tear down and rebuild their webs every night, recycling the silk by eating it. Others maintain the same web for days, patching damaged sections as needed.
Are They Dangerous?
Orb weavers pose no meaningful risk to people or pets. They are docile, non-aggressive spiders that will flee at the first sign of a threat, either by running or dropping out of their web on a dragline. Biting is a last resort, and it only happens if the spider is physically pressed against skin with no escape route.
On the rare occasion a bite does happen, symptoms are mild: slight pain, some numbness, and minor swelling at the site. Nausea and dizziness are uncommon. The venom is designed to subdue small insects, not to harm anything as large as a human. These are not spiders you need to worry about, and they’re not related to any of Colorado’s few medically significant species.
Why You Want Them Around
Orb weavers are highly effective pest control. A single spider can catch dozens of mosquitoes, gnats, flies, and other nuisance insects every night. Their webs near porch lights are especially productive because the light draws insects directly into the trap. Letting an orb weaver stay on your property means fewer biting insects around your home at no cost to you.
Relocating Without Harming Them
If a spider has built its web across a walkway, doorframe, or somewhere you’d rather it not be, relocation is simple. Place a cup or jar over the spider, slide a piece of paper underneath, and carry it to another part of your yard. A fence post, garden trellis, or the far edge of a flower bed all work well. The spider will build a new web within a day. There’s no reason to kill orb weavers, and pest management professionals actively encourage moving them rather than eliminating them, since they benefit the surrounding landscape.
Colorado’s orb weaver season runs roughly from late July through the first hard frost in October. The spiders are most visible in September and early October, when females are fully grown and maintaining large webs to fuel egg production before winter. After the first freeze, the adults die, leaving behind egg sacs that will hatch the following spring and start the cycle again.