In a natural environment, insects live in different microhabitats varying in their humidity. Because insect adhesive mechanism at least partly relies on the capillary force, it is natural to assume that environmental humidity may considerably influence insect attachment. However, this aspect has been neglected in the literature so far. We present the first experimental study demonstrating the influence of the exposure to moist surfaces on the attachment of Colorado potato beetles Leptinotarsa decemlineata. Male beetles were kept at either a dry or moist condition with varying duration of stay for a period up to 160 min. Using centrifugal force tester, their friction forces were then measured on a plexiglas surface. The results show significant differences in force depending on the kind of pre-conditioning. A temporary stay in dry environment had no significant impact on the generated friction forces within the tested time scale. After walking on moist filter paper, forces increased significantly up to 171% of the initial forces measured after 1 min of preconditioning. These results show that insects of the same species may be strongly influenced in their attachment by environmental conditions. The second important conclusion is that results of different experimental studies on insect attachment can hardly be compared if they were performed under different environmental conditions.