Orb spiders demonstrate an impressive ability to adapt their web-building behavior to a wide range of environmental and physiological factors. However, the mechanisms behind this plasticity remain poorly understood. Behavioral plasticity can be categorized as either developmental, where new neural pathways arise from learning, or activational, which rely on more costly pre-existing neural pathways. Here I argue that orb spiders and their webs in general and their response to spatial constraints in particular make an ideal model system in which to explore these two mechanisms further. I show that the spider Eustala illicita (O. Pickard-Cambridge 1889) immediately modifies its first orb web after being placed in spatially confined experimental frames without showing subsequent improvements in design of the second web. Thus, these data are in accord with the hypothesis that this spider relies on activational behavioral plasticity, which might be linked to its preferred habitat in the wild.