This paper presents an immobilization-based control method for spider-like robots that move quasistatically in tunnel environments. The control method is based on an immobilization theory which ensures that an immobile spider mechanism is stabilized by the naturally occurring compliance at the contacts. Based on this result, we present a position control law for general Mimbed spider robots. We show that if the controller's stiffness (i.e. proportional gain) is above a lower limit determined by the spider and environment parameters, stability of the closed-loop spider system is guaranteed. Next we present dynamic simulations of a spider robot moving in a tunnel under the influence of the immobilization-based control law. The simulations show excellent convergence properties of the control algorithm. A four-legged spider prototype has been built, and we conclude with a description of our initial experiments with this spider.