About Callobius claustrarius (Hahn, 1833)
Callobius claustrarius is a species of spider that belongs to the family Amaurobiidae. Males of this species grow to 8 millimeters in length, while females reach approximately 11 millimeters. Its head and legs are reddish brown, and its abdomen is dark grey with a large brown area dotted with lighter brown specks. Adult Callobius claustrarius are active and can be found from autumn through to spring. This species is native to the Palearctic realm. In Europe, it occurs in mountainous regions, particularly in old, moist forests where it lives under rocks. Callobius claustrarius is considered a rather rare species. One subspecies, C. claustrarius balcanicus (first described by Drensky in 1940), is found only in Bulgaria.
