Western Black Widow spiders (Latrodectus hesperus) are found in Colorado. Encounters are infrequent, and bites are rare. Understanding these arachnids helps residents coexist safely.
Identifying Black Widows in Colorado
Identifying the Western Black Widow involves recognizing the adult female. Females typically have a shiny, jet-black body and a rounded abdomen, measuring 6.4 to 13 millimeters (1/4 to 1/2 inch). Their most recognizable feature is a bright red or orange hourglass-shaped mark on the underside of the abdomen. This mark can sometimes appear as two separate spots or be faded.
Male Western Black Widows are considerably smaller, 3.2 to 6.4 millimeters (1/10 to 1/4 inch), and are generally lighter in color, often light brown or gray with banded legs. Males may also have an hourglass marking, typically yellow or orange instead of red. Immature spiders, both male and female, can display gray or light brown bodies with banding patterns and may have red, orange, or yellow spots and stripes on the top of their abdomen, with markings becoming darker as they mature.
Where Black Widows Are Found
Western Black Widows prefer dark, secluded, undisturbed environments, typically constructing irregular, tangled webs close to the ground. Common outdoor locations include woodpiles, sheds, garages, rock crevices, and areas under debris or outdoor furniture. They often nest near holes made by small animals or around construction openings.
Although less common, these spiders can also be found indoors in undisturbed areas like basements, crawl spaces, attics, and storage, particularly in cardboard boxes or rarely-worn shoes. They avoid high-traffic areas, preferring quiet corners or pipe holes. During cooler months, they may seek warmer indoor shelter.
Encountering Black Widows Safely
Minimizing encounters involves maintaining a tidy living space and exercising caution in their preferred habitats.
Regularly decluttering storage areas, attics, basements, and outdoor spaces removes potential hiding spots. Sealing cracks and gaps in your home’s foundation, walls, and around windows and doors prevents them from entering. Using plastic bins with tight-fitting lids for storage instead of cardboard boxes helps deter them.
When working in areas where black widows might reside, such as gardening, moving woodpiles, or cleaning out sheds, wear thick gloves, long-sleeved shirts, and closed-toe shoes for protection. Before putting on shoes or clothing stored in undisturbed areas, shake them out. If a black widow is spotted, remain calm; they generally only bite if threatened. For safe removal, a glass jar and a piece of paper can be used to gently capture the spider and release it outdoors, or a vacuum cleaner can be effective.
Understanding Black Widow Bites
A black widow spider bite may initially feel like a mild pinprick or go unnoticed. Within 30 to 60 minutes, symptoms typically develop and can intensify over several hours. The venom, a neurotoxin called latrotoxin, affects the nervous system and can cause muscle cramps and spasms that spread from the bite site, along with severe pain in the abdomen, back, or chest. Other common symptoms include nausea, vomiting, sweating, headache, and sometimes high blood pressure.
While black widow bites are rarely fatal for healthy adults, they can be more serious for vulnerable individuals like young children, the elderly, or those with compromised immune systems. If bitten, first aid involves washing the wound with soap and water and applying a cold pack or ice to reduce swelling and pain. Seeking medical attention is recommended, especially if symptoms develop or worsen, to ensure proper assessment and care.