The brown recluse spider, Loxosceles reclusa, is an arachnid that generates concern due to the necrotic nature of its venom. This species is known for its reclusive nature, preferring dark and undisturbed environments. This article clarifies the scientific consensus regarding the distribution of the brown recluse, specifically addressing its establishment within Wyoming.
Established Presence in Wyoming
Scientific evidence indicates that the brown recluse spider is not established in Wyoming, meaning the state does not contain self-sustaining, breeding populations. Entomologists at the University of Wyoming confirm that while isolated individuals have been documented, these findings are exceptionally rare. Verified specimens found over two decades were classified as “hitchhikers,” accidentally transported into the state.
These isolated spiders typically arrive in boxes, furniture, or shipping containers from their native range. They cannot thrive or reproduce effectively in the non-native climate. An established population requires a stable environment where the spiders can consistently complete their life cycle. The few specimens found are isolated incidents, not evidence of a local colony.
The Native Range and Environmental Limits
The brown recluse is not established in Wyoming due to the limits of its natural geographic range. The species is natively found in the south-central Midwest and Gulf Coast states, with established populations across 16 states, including Missouri, Kansas, and Illinois. This core habitat provides the moderate temperatures and low humidity the spiders require to flourish.
The brown recluse is not well-adapted to the cooler, drier conditions characteristic of Wyoming’s climate. Outside of their native zones, they are restricted almost exclusively to buildings, and even then, they struggle to survive. Their inability to survive the harsh outdoor conditions of Wyoming prevents the formation of stable, widespread populations.
Distinguishing Brown Recluse Look-alikes
Because the brown recluse is not native to Wyoming, many reported sightings result from misidentification of common local spiders. Harmless species in the state, such as the barn funnel weaver or various wolf spiders, share a similar general brown coloration, leading to public anxiety.
Proper identification of the Loxosceles reclusa relies on specific physical characteristics. Unlike most spiders which possess eight eyes, the brown recluse has only six eyes, arranged in three pairs, or dyads, in a semi-circle on the cephalothorax. A primary identifying feature is the dark, violin-shaped marking on the top of the cephalothorax, with the neck of the “violin” pointing toward the abdomen.
Relying solely on the violin mark can be misleading, as other spiders may have similar patterns. The recluse spider also has uniformly colored legs and a uniformly colored abdomen, meaning they lack any stripes, spots, or bands of color. Conversely, common Wyoming look-alikes like the barn funnel weaver often have thicker, hairier legs with faint dark barring and a two-toned abdomen, and they possess the typical eight-eye arrangement.