As summer heat peaks and we head into fall, spider behavior in Colorado begins to shift. Understanding these changes can help you manage these eight-legged visitors more effectively in cities like Arvada, Golden, and Evergreen.

What spiders are in Colorado? Colorado is home to various spider species. Here are some you might encounter:

1. Common House Spider (Parasteatoda tepidariorum):
   • Behavior in Fall: As temperatures drop, these spiders move indoors in search of warmth. You’ll often find them in corners and behind furniture in places like Wiggins and Windsor. They focus on repairing their webs and catching any insects that get inside.
   • Webs: Their webs are messy and scattered, perfect for trapping a variety of bugs.
   • Diet: They feed on small insects, helping to manage indoor pests.
2. Black House Spider (Badumna insignis):
   • Behavior in Fall: These spiders prefer dark, hidden spots like window frames and eaves. As fall approaches, they reinforce their webs and increase their hunting to prepare for the colder months in cities such as Englewood and Cherry Creek.
   • Webs: They create funnel-shaped webs to capture prey.
   • Diet: They consume flies, moths, and beetles that get caught in their webs.
3. Wood Spider (Family Lycosidae):
   • Behavior in Fall: These active hunters tend to come indoors when it gets cooler. Unlike web-building spiders, wood spiders hunt their prey directly. In fall, they become more visible as they search for insects in areas like Golden and Evergreen.
   • Hunting: They are often seen running across floors and walls.
   • Diet: They feed on a variety of insects and small arthropods, helping to keep your home’s pest population in check.
4. Brown House Spider (Steatoda grossa):
   • Behavior in Fall: Sometimes confused with the brown recluse, these spiders seek out warm, quiet places inside your home during the fall. They are not aggressive and tend to remain hidden in places such as Arvada and Wiggins.
   • Webs: They build tangled webs in dark areas such as basements and attics.
   • Diet: They prey on small insects and other spiders.

As August heats up and fall approaches, spider behavior in Colorado shifts in several ways:

1. Increased Activity: Spiders become more active in warm weather due to mating and hunting. Males, in particular, are more visible as they search for females across the state, from Englewood to Cherry Creek.
2. Migration Indoors: To escape the heat outside, spiders come indoors looking for cooler, stable conditions. This is especially true for common house spiders and brown house spiders. Inside, they find not only a consistent temperature but also ample food.
3. Web Building: With more insects available, spiders build and repair their webs more frequently. They aim to capture as much prey as possible before the weather turns cold.
4. Hunting Patterns: Non-web-building spiders, like wood spiders, increase their hunting activity during the warmer months. They become more noticeable as they hunt for food.
5. Mating Season: Late summer and early fall are prime times for spider mating. Male spiders are more active in search of females, leading to increased spider sightings.

What poisonous spiders are in Colorado? While most spiders are harmless, a few are venomous:

1. Western Black Widow (Latrodectus hesperus):
   • Appearance: Recognizable by its shiny black body and red hourglass marking.
   • Habitat: Found in dark, undisturbed areas such as garages and basements.
   • Venom: Bites can cause severe pain and muscle cramps but are rarely fatal.
2. Brown Recluse Spider (Loxosceles reclusa):
   • Appearance: Notable for its violin-shaped marking.
   • Habitat: Less common in Colorado but can be found.
   • Venom: Can cause painful skin lesions and systemic symptoms, though sightings are rare.

Most brown spiders you encounter are likely harmless brown house spiders, not brown recluse spiders.

A close-up image of a common barn funnel weaver in Colorado. Spiders tend to come inside more as summer ends, and fall progresses.

Seeing more spiders in late summer and fall is normal for several reasons:

1. Temperature Regulation: Spiders come indoors as temperatures drop to find stable conditions. This doesn’t necessarily indicate an infestation.
2. Mating Season: Many spiders mate in late summer and fall, making males more noticeable as they seek out females.
3. Prey Availability: Increased insect activity means more food for spiders, leading to higher spider activity.

To reduce spider encounters, consider these tips:

1. Regular Cleaning: Dust and vacuum corners, behind furniture, and other areas where spiders might build webs.
2. Seal Entry Points: Close off cracks and gaps around windows, doors, and foundations to keep spiders out.
3. Outdoor Maintenance: Keep your yard free of debris, woodpiles, and clutter where spiders might hide.
4. Proactive Professional Pest Control: Even if you only see a few spiders, addressing potential issues early is wise. Proactive professional pest control services from OBEX can prevent larger problems. We provides tailored solutions to Colorado’s unique environment, ensuring a safer, more comfortable home.

Understanding spider behavior in Colorado as the weather changes helps you manage these creatures effectively. By recognizing different species and their habits, you can take the right steps to prevent unwanted encounters. For added peace of mind, OBEX offers expert services to keep your home spider-free.

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