brown recluse spider or violin spider, poisonous nocturnal spider, Loxoceles reclusa, most common in the SE and S central United States. Adults are 3/8 in. (10 mm) long and are light brown with a dark, violin-shaped mark on the back near the head. In humans their venom kills the tissue surrounding a bite and leaves a deep sore, but only rarely does a bite result in death.