Brown recluse spiders build asymmetrical (irregular) webs that frequently include a shelter consisting of disorderly thread. They frequently build their webs in woodpiles and sheds, closets, garages, plenum spaces, cellars, and other places that are dry and generally undisturbed. When dwelling in human residences they seem to favor cardboard, possibly because it mimics the rotting tree bark which they inhabit naturally. They have also been encountered in shoes, inside dressers, in bed sheets of infrequently used beds, in clothes stacked or piled or left lying on the floor, inside work gloves, behind baseboards and pictures, in toilets, and near sources of warmth when ambient temperatures are lower than usual. Human-recluse contact often occurs when such isolated spaces are disturbed and the spider feels threatened. Unlike most web weavers, they leave these lairs at night to hunt. Males move around more when hunting than do females, which tend to remain nearer to their webs. The spider will hunt for firebrats, crickets, cockroaches, and other soft-bodied insects.
The spider usually bites only when pressed against the skin, such as when tangled within clothes, towels, bedding, inside work gloves, etc. Many human victims report having been bitten after putting on clothes that had not been worn recently, or had been left for many days undisturbed on the floor. However, the fangs of the brown recluse are so tiny they are unable to penetrate most fabric.
The bite frequently is not felt initially and may not be immediately painful, but it can be serious. The brown recluse bears a potentially deadly venom. Most bites are minor, however, a small number of brown recluse bites do produce severe lesions. For those with sensitivity levels, a small white blister appears at the bite-site soon after the bite. The tissue may become hard. Lesions are dry, blue-gray or blue-white patches with ragged edges surrounded by redness. This color pattern has yielded the nickname “red, white and blue.” In severe reactions, the bite-site can develop a “volcano lesion.” The damaged tissue becomes gangrenous and leaves an open wound that can be as large as a human hand. It can take eight weeks or longer for full recovery, and scars may result. There are cases of victims experiencing restlessness, generalized itching, fever, chills, nausea, vomiting or shock after a bite. Fatalities are rare, but the bites are more dangerous to young children, the elderly, and those in poor health.
If bitten, go immediately to a medical profession and bring the spider if possible, for identification purposes. There is no effective commercial antivenom.