The brown recluse spider is tan to orange-yellow on the front part of the body (cephalothorax). This body section has a dark violin shape. The abdomen is oval, hairy, gray-brown to gray and lacking markings. The legs are very long. Six eyes are present and arranged in three pairs. The female is about one-half inch in length, while the male is about one-fourth inch long.
The brown recluse may be found in the southern two-thirds of Illinois. It often lives inside houses in dark places like closets and dressers. It also can be found outdoors under rocks, logs or debris. This spider builds a loose web but leaves it at night to hunt for its insect prey. The female deposits an egg sac in the web in fall and guards it until she dies when cold weather occurs (outdoor spiders only). The eggs hatch in spring. Females living in houses may survive for several years. The venom of the brown recluse is considered dangerous and occasionally fatal to humans, although people are rarely bitten.