Colorado’s diverse ecosystems, ranging from arid plains to mountainous forests, are home to a fascinating array of spider species. While most are harmless and play a crucial role in controlling insect populations, identifying them can be both intriguing and practical. Here’s a comprehensive guide to seven common spiders you might encounter in Colorado, complete with identification tips and behavioral insights.
1. Black Widow (Latrodectus variolus)
The Black Widow is one of the most recognizable—and feared—spiders in Colorado. While its bite is venomous and can cause severe symptoms, bites are rare and typically occur only when the spider is threatened.
Identification:
- Color: Jet-black with a distinctive red hourglass marking on the underside of the abdomen.
- Size: Females are 1.5 inches long (including legs); males are smaller and lighter in color.
- Habitat: Prefers dark, secluded areas like woodpiles, sheds, and basements.
Behavior: Nocturnal and reclusive, often building messy, irregular webs.
2. Hobo Spider (Eratigena agrestis)
Pro: Often confused with the more dangerous brown recluse, the hobo spider is less venomous and rarely bites humans.
Con: Its bite can cause localized necrosis in rare cases, though its aggression is minimal.
Identification:
- Color: Brownish with faint yellow markings on the abdomen.
- Size: Up to 0.5 inches (body only).
- Habitat: Found in dark, damp areas like basements, garages, and firewood piles.
Behavior: Builds funnel-shaped webs and is active at night.
3. Wolf Spider (Lycosidae family)
Wolf spiders are formidable hunters, relying on speed and agility rather than webs to catch prey.
Identification:
- Color: Brown or gray with darker markings.
- Size: Up to 1.5 inches (including legs).
- Habitat: Ground-dwelling, often found in gardens, fields, and forests.
Behavior: Active hunters that chase down prey. Females carry their egg sacs and young on their backs.
4. Jumping Spider (Salticidae family)
Hunting Strategy: These spiders don’t build webs to catch prey. Instead, they stalk and pounce with incredible precision.
Identification:
- Color: Bright and varied, often with iridescent patterns.
- Size: Small, typically 0.25–0.75 inches.
- Habitat: Found on walls, fences, and vegetation.
Behavior: Known for their excellent vision and curious nature. They may even tilt their heads to observe humans.
5. Orb Weaver (Araneidae family)
Orb weavers are the architects of the spider world, spinning intricate, circular webs that can span several feet.
Identification:
- Color: Varied, often with bright patterns on the abdomen.
- Size: Up to 1 inch (body only).
- Habitat: Gardens, meadows, and forests.
Behavior: Active at night, rebuilding their webs daily. Harmless to humans.
6. Cellar Spider (Pholcidae family)
Pro: Often called "daddy longlegs," these spiders are beneficial, feeding on other spiders and insects.
Con: Their long, thin legs and erratic movements can be unsettling to some.
Identification:
- Color: Pale yellow or light brown.
- Size: Tiny body (0.1–0.2 inches) with legs up to 2 inches long.
- Habitat: Cellars, basements, and corners of rooms.
Behavior: Builds loose, irregular webs and vibrates rapidly when threatened.
7. Bold Jumping Spider (Phidippus audax)
This charismatic spider is a favorite among arachnologists for its bold behavior and striking appearance.
Identification:
- Color: Black with white or metallic green markings.
- Size: Up to 0.5 inches.
- Habitat: Gardens, walls, and fences.
Behavior: Known for its curiosity and ability to jump up to 50 times its body length.
How to Safely Coexist with Colorado Spiders
- Avoid Provocation: Most spiders bite only when threatened.
- Seal Entry Points: Use caulk to close gaps in windows and doors.
- Reduce Clutter: Keep basements and garages tidy to minimize hiding spots.
- Use Natural Repellents: Essential oils like peppermint or vinegar can deter spiders.
Are there venomous spiders in Colorado?
+Yes, the Black Widow is the most venomous spider in Colorado. However, bites are rare, and fatalities are extremely uncommon.
How can I tell if a spider is dangerous?
+Dangerous spiders like the Black Widow have distinct markings (e.g., the red hourglass). Most spiders in Colorado are harmless.
Do spiders in Colorado build webs indoors?
+Some species, like cellar spiders and orb weavers, may build webs indoors, especially in dark, undisturbed areas.
What should I do if I find a spider in my home?
+If it’s harmless, gently relocate it outdoors. For venomous spiders, use a container to trap and release it far from your home.
How can I prevent spiders from entering my home?
+Seal cracks, keep your home clean, and reduce outdoor lighting to minimize insect attraction.
Colorado’s spiders are a testament to the state’s biodiversity. While some may evoke fear, understanding their behavior and role in the ecosystem can foster appreciation for these eight-legged neighbors. With this guide, you’re now equipped to identify and coexist with the most common spiders in the Centennial State.
