The brown recluse spider, Loxosceles reclusa, is associated with public anxiety due to its reputation for causing necrotic wounds. This species carries a venom that can sometimes lead to loxoscelism, a condition characterized by the breakdown of tissue at the bite site. Many people living outside the spider’s native habitat are concerned about its potential presence. Understanding the actual geographic distribution of this arachnid is the first step in accurately assessing any local risk.
The Definitive Answer: Are They Established in Washington State?
The brown recluse spider is not established in Washington State. This species is primarily native to the Midwest and South Central regions of the United States, with its range extending from Nebraska down to Texas and eastward into Ohio and Georgia. Washington State lies far outside this established native range, meaning it lacks stable, breeding populations.
Any documented appearances of Loxosceles reclusa in the Pacific Northwest are considered isolated, non-native incidents. These rare occurrences involve transient spiders that have been accidentally introduced through human activity, typically transported via freight, luggage, or shipping containers. The chances of these isolated individuals surviving long enough to establish a population in Washington’s climate are negligible.
Identifying Features of the Brown Recluse
The primary reason for public concern is often the misidentification of common household spiders as the brown recluse. The true Loxosceles reclusa possesses several distinct anatomical features that differentiate it. The most famous mark is the dark, violin-shaped pattern located on the dorsal side of the cephalothorax, with the neck of the “violin” pointing toward the abdomen.
A more reliable distinguishing characteristic is the unique eye arrangement. Unlike most spiders, which possess eight eyes arranged in two rows, the brown recluse has only six eyes. These six eyes are arranged in three pairs, or dyads, positioned in a semi-circle across the front of the cephalothorax. Furthermore, a true recluse spider lacks complex patterns on its abdomen or legs. Its legs are uniformly colored and do not feature stripes, bands, or noticeable spines.
Common Washington State Look-Alikes
The high rate of misidentification in Washington State is typically due to the prevalence of several native brown spider species that share a similar coloration or shape. The Giant House Spider, Eratigena atrica, is a very common species in Washington homes, especially in basements and garages. Although large and fast-moving, these spiders are harmless to humans and help control insect populations indoors.
Another frequently misidentified species is the Hobo Spider, Eratigena agrestis, which is also common throughout Washington. Hobo spiders have a robust brown appearance, which leads to them being blamed for bites attributed to the brown recluse. Hobo spiders, like most other spiders, possess eight eyes arranged in two parallel rows, which immediately rules out a brown recluse identification.
For individuals who suspect a spider bite has caused a necrotic wound, medical professionals emphasize that most such injuries are misdiagnosed. Conditions like bacterial infections, most notably Methicillin-resistant Staphylococcus aureus (MRSA), are far more common causes of necrotic skin lesions than any spider bite in the Pacific Northwest. The only two spiders in Washington of medical significance are the Black Widow and the Yellow Sac Spider, neither of which causes the necrotic injury associated with loxoscelism.