Black widow spiders are known for their distinctive appearance and potent venom, prompting questions about their presence and safe interaction. Understanding their distribution and habits promotes informed safety practices.
Presence and Habitat in Colorado
Black widow spiders are found in Colorado, with the Western black widow (Latrodectus hesperus) being the most common species. These spiders are shy and not aggressive, typically biting only when provoked or defending their web.
Within Colorado, black widows prefer to establish their irregular, messy webs in dark, undisturbed locations close to the ground. Common outdoor habitats include:
Woodpiles
Under rocks
Sheds
Garages
Outdoor furniture
Construction openings or low shrubs
Indoors, they can inhabit basements, crawl spaces, and corners of rooms or outbuildings, especially as temperatures cool. They are primarily nocturnal hunters, waiting for prey to become ensnared in their sticky webs.
Identification and Safety Measures
Identifying a black widow spider involves recognizing distinct physical characteristics, particularly of the female. The adult female Western black widow is shiny black, with a spherical abdomen measuring around 6.4 to 8.5 millimeters (1/4 to 1/3 inch). Her most recognizable feature is a red or orange hourglass-shaped mark on the underside of her abdomen. This hourglass shape can vary, appearing as two unconnected spots, a rectangle, or even being faded.
Male black widows are smaller than females, measuring 3.2 to 6.4 millimeters (1/10 to 1/4 inch), and are often light brown or gray with banded legs. Their hourglass marking is typically orange or yellow and less distinct. Immature spiders appear different, with gray or light brown bodies and banding patterns, and their hourglass shape becomes more defined as they mature.
To minimize encounters with black widows, take several preventative measures around the home and yard. Reduce clutter in basements, garages, and storage areas to remove potential hiding spots. Store firewood away from the house and off the ground, as they frequently hide in woodpiles. Seal cracks and gaps in your home’s foundation, around windows, and doors to prevent spiders from entering indoor spaces.
When working outdoors in areas where black widows might reside, such as gardening or cleaning sheds, wearing thick gloves and long sleeves is a practical safety measure. Shaking out shoes and clothing before wearing them can prevent accidental bites. Maintaining outdoor lighting can also help, as yellow or sodium vapor lights attract fewer insects, which are a primary food source for these spiders.
If a black widow bite is suspected, symptoms often include immediate mild pain or a pinprick sensation at the bite site. This is followed by more intense muscle cramps and pain, particularly in the abdomen, chest, or back, which can worsen over several hours. Other symptoms include nausea, vomiting, sweating, headache, and general weakness. Swelling and redness at the bite site are common, and a blister may form.
Immediate first aid for a black widow bite involves cleaning the area with soap and water. Apply a cold compress or ice pack to the bite to reduce pain and swelling, and elevate the affected limb. Seek professional medical attention for any suspected black widow bite, especially for children, the elderly, or individuals with underlying health conditions, as they may experience more severe reactions. While fatalities from black widow bites are rare, prompt medical evaluation ensures appropriate care and symptom management.