Many animals bear adhesive pads on their limbs to attach to a variety of surfaces. Previous force measurements on pads of the great green bushcricket (Tettigonia viridissima) have shown that the maximum adhesion force depends on the initially applied force [Jiao et al., 2000. J. Exp. Biol. 203 (12), 1887-1895]. We have developed a model that explains this behaviour. The adhesive pad is modelled as a flexible layer that consists of independent linear springs connected to a rigid sphere. Each spring can generate an adhesive contact with the surface by means of the capillary force or due to van der Waals interactions. The model shows a very good agreement with the experiments.