The feet of the jumping spider Evarcha arcuata attach to rough substrates using tarsal claws. On smooth surfaces, however, attachment is achieved by means of a claw tuft, the scopula. All eight feet bear a tarsal scopula, which is equipped with setae, these again being covered by numerous setules. In E. arcuata, an estimated 624,000 setules, with a mean contact area of 1.7 x 10(5) nm(2), are present. The spider's entire contact area thus totals 1.06 x 10(11) nm(2). Adhesion to the substrate does not depend on the secretion of an adhesive fluid. Analysis via atomic force microscopy (AFM) shows that a single setule can produce an adhesive force (F(a)) of 38.12 nN perpendicular to a surface. Consequently, at a total F(a) of 2.38 x 10(-2) N and a mean body mass of 15.1 mg, a safety factor (SF; F(a)/F(m), where F(m) is weight) of 160 is achieved. Tenacity (tau(n); F(a)/A, where A is area of contact) amounts to 2.24 x 10(5) N m(-2).