Identifying A Brown Recluse Vs. An American House Spider A small violin-shaped marking on a brown spider's back is a surefire sign that you're looking at a brown recluse.

The brown recluse spider is one of three venomous spiders in the U.S. The spiders can be identified by the dark brown, violin-shaped marking on their back.

The brown recluse spider Size: Body two-fifths of an inch long. Leg span about an inch. Color: Light brown. Distinguishing characteristics: Dark brown violin-shaped spot on back near the head.