This U.S. State Has the Largest Brown Recluse Infestation Numbers

The brown recluse (Loxosceles reclusa) is a venomous spider with a violin-shaped marking on its back. A bite from a brown recluse is considered medically significant and can cause tissue damage, blistering, and, in some cases, necrotic ulcers requiring medical attention. Systemic symptoms, such as fever, chills, and nausea, can also occur, with severe reactions being more common in children and older adults. Missouri, Kansas, Oklahoma, and Arkansas have particularly widespread and common populations of brown recluses. Other states with significant brown recluse spider populations include Texas, Indiana, Illinois, Kentucky, Tennessee, and Georgia. Continue reading to discover which U.S. State has the largest brown recluse infestation numbers.

Recluse Species Found in the United States

There are over 140 species of recluse spiders worldwide, with 13 found in the United States: 11 native species and two non-native species that have become established. The most well-known in the U.S. is the brown recluse. Native recluse spiders present in the United States are:

• Apache recluse (𝐿𝑜𝑥𝑜𝑠𝑐𝑒𝑙𝑒𝑠 𝑎𝑝𝑎𝑐ℎ𝑒𝑎): Found in the southwestern United States.
• Arizona recluse (𝐿𝑜𝑥𝑜𝑠𝑐𝑒𝑙𝑒𝑠 𝑎𝑟𝑖𝑧𝑜𝑛𝑖𝑐𝑎): Found in Arizona, California, and Texas.
• Big Bend recluse (𝐿𝑜𝑥𝑜𝑠𝑐𝑒𝑙𝑒𝑠 𝑏𝑙𝑎𝑛𝑑𝑎): Found in Texas and Mexico.
• Desert recluse (𝐿𝑜𝑥𝑜𝑠𝑐𝑒𝑙𝑒𝑠 𝑑𝑒𝑠𝑒𝑟𝑡𝑎): Primarily inhabits the Sonoran and Mojave deserts of California, Nevada, and Arizona.
• Martha’s recluse (𝐿𝑜𝑥𝑜𝑠𝑐𝑒𝑙𝑒𝑠 𝑚𝑎𝑟𝑡ℎ𝑎): Found in California.
• Texas recluse (𝐿𝑜𝑥𝑜𝑠𝑐𝑒𝑙𝑒𝑠 𝑑𝑒𝑣𝑖𝑎): Found in Texas.
• Russell’s recluse (𝐿𝑜𝑥𝑜𝑠𝑐𝑒𝑙𝑒𝑠 𝑟𝑢𝑠𝑠𝑒𝑙𝑙𝑖): Found in California.
• Baja recluse (𝐿𝑜𝑥𝑜𝑠𝑐𝑒𝑙𝑒𝑠 𝑝𝑎𝑙𝑚𝑎): Found in California.
• Tucson recluse (𝐿𝑜𝑥𝑜𝑠𝑐𝑒𝑙𝑒𝑠 𝑠𝑎𝑏𝑖𝑛𝑎): Found in Arizona.
• Grand Canyon recluse (𝐿𝑜𝑥𝑜𝑠𝑐𝑒𝑙𝑒𝑠 𝑘𝑎𝑖𝑏𝑎): Found in Arizona. 

Non-native recluse species: 

• Chilean recluse (𝐿𝑜𝑥𝑜𝑠𝑐𝑒𝑙𝑒𝑠 𝑙𝑎𝑒𝑡𝑎): Established in a limited area of Los Angeles County.
• Mediterranean recluse (𝐿𝑜𝑥𝑜𝑠𝑐𝑒𝑙𝑒𝑠 𝑟𝑢f𝑒𝑠𝑐𝑒𝑛𝑠): Established in some areas of the Northeast, including the steam tunnels of Penn State. 

All recluse spiders produce venom that is capable of causing necrotic (flesh-rotting) skin lesions. However, the vast majority of recluse bites, including those of the brown recluse, heal on their own and are not medically significant. 

The State with the Largest Brown Recluse Infestation

Missouri is widely recognized as having one of the highest brown recluse spider populations in the United States, with reports of significant infestations in homes and buildings. It is difficult and likely inaccurate to cite an exact number for Missouri’s brown recluse population. Estimating their numbers is challenging because of the spiders’ reclusive nature, small size, and wide distribution. Pest control reports and anecdotal evidence suggest that Missouri may have more brown recluse infestations than most other U.S. states, though comprehensive scientific studies comparing all states are lacking.

A Disturbing Infestation

In 2007, a couple made headlines when they found they were not the only ones occupying their recently purchased Missouri home. In what was described as a freak event, Brian and Susan Trost soon realized their home was infested with a horrific number of brown recluse spiders. Further investigation revealed that between 4,600 and 6,000 brown recluses had taken up residence in air vents, the pantry ceiling, and the fireplace.