changes in environmental characteristics may generate plastic behavioral responses. we evaluated whether the risk of mechanical damage by the fall of plant material affected the resistance of webs of the spider thaida peculiaris, and explored some of the associated mechanisms. compared to protected sites, webs in exposed sites were more resistant, their silk lines supported more weight, and their mesh widths were higher. these results suggest that the risk of mechanical damage is a selective pressure that generates plastic behavioral responses in the building of webs. we discussed the adaptive value of investing in more resistant silk or changing mesh width, and the direct and indirect processes used by spiders to evaluate the protection level of a site. this work illustrates how the organisms may plastically respond to variable environments by modifying certain characteristics of their constructions.