Brown recluse spiders are not naturally established in Colorado. While reports of brown recluse bites have occurred, these instances are often unverified or involve spiders accidentally transported into the state.
Natural Habitat and Range
The brown recluse spider, Loxosceles reclusa, is native to the south-central United States. Their established geographic range extends from central Texas to western Georgia and north to states like Kentucky, Nebraska, and Ohio. These spiders thrive in warm, dry, undisturbed environments, often found outdoors under rocks and logs, or indoors in dark, secluded areas like basements, attics, and closets.
Colorado’s climate and ecological conditions do not support self-sustaining populations of brown recluse spiders. Any brown recluse found in Colorado is likely an isolated individual that has “hitchhiked” from its native range, often transported in boxes, furniture, or other belongings. Such accidental transport does not indicate an established population.
Common Look-Alikes in Colorado
Many local spiders are frequently mistaken for brown recluses due to similar appearances or general brown coloration. Funnel weaver spiders are commonly misidentified as brown recluses in Colorado. These spiders have hairy bodies, four pairs of eyes, and often banded or patterned legs, distinguishing them from the brown recluse.
Other spiders often mistaken for brown recluses include wolf spiders, hobo spiders, and common house spiders. Wolf spiders are large, hairy, and dark brown with pale markings. Hobo spiders, also light to medium brown, have oblong bodies and faint markings. Cellar spiders, with their very long legs and a body longer than wide, are also sometimes confused with brown recluses.
Identifying a Brown Recluse
Accurate identification of a brown recluse spider requires careful observation of specific features. The most recognized characteristic is a dark, violin-shaped marking on the spider’s cephalothorax, with the “neck” of the violin pointing towards the abdomen. This marking can vary in intensity and may not be present in very young spiders.
A more definitive diagnostic feature is the brown recluse’s eye arrangement; unlike most spiders with eight eyes, they possess six eyes arranged in three pairs in a semicircle pattern. Additionally, brown recluse spiders have uniformly colored legs without spines or bands, and their abdomens are typically uniform in color, lacking stripes or patterns.
What to Do About Spider Bites
Most spider bites are not serious and typically result in only minor symptoms such as localized redness, swelling, and pain. If bitten, it is recommended to clean the area with mild soap and water. Applying a cold compress or ice pack can help reduce pain and swelling. Elevating the affected area can also be beneficial.
Medical attention should be sought if the bite causes severe pain, spreading redness, signs of infection like pus or increasing warmth, or systemic symptoms such as fever, chills, nausea, or body aches. While brown recluse bites can cause more severe reactions, they are exceedingly rare in Colorado. Most spider bites in the state are from less medically significant species.