What You Need to Know About Black House Spiders in Colorado Homes

Black House Spiders in Colorado - What You Need to Know

Of the hundreds of spider species found in Colorado, one of the most common - and concerning - is the black house spider. With a dark brown to black coloration and globe-shaped abdomen, black house spiders are medium-sized arachnids that construct messy, tangled webs in and around homes. While not considered aggressive, they do possess a venomous bite that can cause mild symptoms in humans.

Keep reading to learn more about identifying black house spiders, where they live, what their bite feels like, and how to prevent and safely remove them from your Colorado home.

Appearance and Identification

Black house spiders (Badumna insignis) belong to the Desidae family and are indigenous to Australia. However, they have spread via commerce to parts of North America, Europe, Asia, South America, and Africa. In the United States, black house spiders are most commonly found along the Pacific Coast and Rocky Mountain region, including Colorado.

Adult black house spiders measure around 10-15 mm (0.4-0.6 inches) in body length. They have a round, dark gray or black abdomen with faint white or gray markings. Their cephalothorax (head region) is slightly lighter in color. They have eight eyes arranged in two straight rows. Their legs are brown or tan with dark bands. Male spiders are slightly smaller than females but otherwise look similar.

One key identifying feature of black house spiders is their messy, chaotic webs. Their non-adhesive webs include tangled, uneven threads and lack any clear pattern or shape. The webs are constructed in dark, undisturbed areas such as attics, sheds, garages and corners of homes.

Habits and Habitats

As their name implies, black house spiders primarily live in and around human homes and structures. They do not survive outdoors or away from sheltered areas. Inside homes, they prefer dry, dark places such as garages, sheds, attics and wall voids. They construct their messy webs in corners, windows, door and window frames and undisturbed storage areas.

Black house spiders are nocturnal and do most of their hunting and web construction at night. During the day, they tend to rest in retreats within their webs. They mainly prey upon insects but also feed on other spiders. The messy web structure helps trap and snare prey as they move through the web.

After mating, the female black house spider produces an egg sac containing 40-100 eggs. The egg sac may be suspended within the web or affixed to surfaces. Spiderlings hatch within a few weeks and begin dispersing after their first molt. Most black house spiders live for 1-2 years. They actively avoid contact with humans but may bite if trapped against the skin.

Bites and Venom

Like all spiders, black house spiders have venom they use to subdue prey. Black house spider venom contains neurotoxins and cytotoxins. While not considered dangerous to most people, black house spider bites can cause various symptoms including:

• Instant pain at the bite site
• Itching, redness and mild swelling
• Mild nausea and headache
• Generalized weakness and fatigue
• Muscle pain and cramps

In rare cases, the bite may trigger severe allergic reactions, fever, increased blood pressure, vomiting or breathing difficulties, especially in young children and the elderly. Seek medical attention if concerning bite symptoms develop.

Black house spider bites can be identified by two small puncture marks surrounded by swelling and redness. Bites commonly occur on arms, legs and torso areas as spiders become trapped against the skin in clothing or bedding.

Spider bites are often confused with other insect bites and stings that trigger similar reactions. Seek medical evaluation to confirm it is a spider bite if you experience severe symptoms or signs of infection such as increased swelling, redness, warmth or pus at the bite site.

Prevention and Safe Spider Removal

To help discourage black house spiders from inhabiting your Colorado home, follow these prevention tips:

• Seal cracks and small entry points on exterior walls
• Install and repair window screens
• Reduce clutter and storage in garages and attics
• Keep bedding and linens away from walls and floors
• Turn off lights to avoid attracting insects they prey on
• Use pesticides or natural repellents around likely entry points

If you spot a black house spider, avoid killing it or using chemical sprays. Their messy webs easily trap insecticide residue. The safest approach is to capture and relocate them.

To remove a black house spider:

1. Protect your hands with gloves or thick cloth
2. Place an open jar or cup over the spider
3. Slip paper or cardboard under the container to trap the spider inside
4. Secure lid over container and release the spider outdoors
5. Clean web remnants with a cloth or vacuum

Avoid crushing spiders, as this releases pheromones that attract other spiders to rebuild webs. Always take caution when removing black house spiders to avoid accidental bites. Seek emergency care if you experience concerning bite symptoms.

Summary

With their dark color, messy webs and proximity to humans, black house spiders are one of the more alarming spider species found in Colorado homes. While their venom can cause discomfort, their bites are not considered medically significant in most cases.

Prevent black house spider encounters by sealing entry points, reducing clutter, installing screens and keeping their preferred habitats dry and undisturbed. Use humane removal and relocation techniques if you spot one, taking care to protect your skin from potential bites.

With proper prevention and awareness of their habits, black house spiders do not need to be feared in your Colorado home.

Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult with a healthcare professional before starting any new treatment regimen.