Insects can walk in unstructured environments such as trees and rocks by changing foot trajectory and coordination pattern between limbs (i.e., interlimb coordination). Although we previously proposed a simple decentralized control scheme using local feedback based on ground reaction force, the control mechanism underlying adaptive foot trajectory in insects’ locomotion has not yet been clarified. To reveal the control mechanism in adaptive foot trajectory, this study conducted biological experiments in which crickets walk up against a slope with inhomogeneous frictional coefficient. Based on experimental results, we propose a decentralized control mechanism in which adaptive foot trajectory changes in response to the slipperiness of the terrain.