The brown recluse spider, Loxosceles reclusa, is a well-known member of the family Sicariidae (formerly placed in a family “Loxoscelidae”).
It is usually between 6–20 mm, but may grow larger. It is brown and sometimes an almost deep yellow color and usually has markings on the dorsal side of its cephalothorax, with a black line coming from it that looks like a violin with the neck of the violin pointing to the rear of the spider, resulting in the nicknames fiddleback spider, brown fiddler or violin spider. Coloring varies from light tan to brown and the violin marking may not be visible.
Recluse spiders build irregular webs that frequently include a shelter consisting of disorderly threads. These spiders frequently build their webs in woodpiles, sheds, closets, beds, garages, plenum, cellars and other places that are dry and generally undisturbed. They seem to favor cardboards when dwelling in human residences, possibly because it mimics the rotting tree bark which they inhabit naturally. They also tend to be found in shoes, inside dressers, in bed sheets of infrequently used beds, in stacks of clothes, behind baseboards, behind pictures and near furnaces. The common source of human-recluse contact is during the cleaning of these spaces, when their isolated spaces are suddenly disturbed and the spider feels threatened. Unlike most web weavers, they leave these webs at night to hunt. Males will move around more when hunting, while the female spiders tend to remain nearer to their webs.
Spiderlings hatch from eggs which are laid from May to July. Eggs are laid in a case of white silken sac. There are approximately 50 eggs in each egg sac. From the egg that is produced from the brown recluse female the spiderlings emerge in 1 month. It takes one year before a spiderling can be considered an adult. It takes a spider about eleven months to reach the adult stage from the time of hatching. Adult brown recluse spiders often live about one to two years. Each female produces several egg sacs over a period of two to three months.
The brown recluse spider is resistant to long periods without food. It can tolerate up to 6 months of extreme drought and scarcity of food.
The venom from a brown recluse spider is extremely venomous. Because of its venom the brown recluse spider is perhaps considered one of the most medically important groups of spiders. Envenomations can result in dermonecrosis and sometimes general systemic illness that can be life threatening; especially for the elderly and children.
To avoid brown recluse spiders, avoid keeping clothing on the floor. Store clothing and shoes inside plastic containers, and shake out all clothing that has been in a hamper before wearing or washing.