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rock weaver

rock weaver spider (Titanoeca brunnea) [male]
Photo © Hank Guarisco

Features and Behaviors

There are four species of rock weaver spiders in the United States. Their abdomen is usually plain-colored. The body color is generally dark brown.

They build sheet webs, usually under rocks, and tend to occupy dry habitats. These spiders use a cribellum instead of spinnerets to release silk. The cribellum is made of plates, and each plate is covered with thousands of tiny spigot openings. These openings release silk strands that are very thin and gathered into silk that appears “woolly.” Adults are active from late spring through early fall.

Illinois Range


Kingdom: Animalia
Phylum: Arthropoda
Class: Arachnida
Order: Araneae
Family: Titanoecidae

Illinois Status: common, native