Recent attention in ecology has focused on factors that influence the foraging behavior of herbivores. We evaluated responses to different arrays of food plants exhibited by an abundant folivore within the tabonuco forest of Puerto Rico. Previous work indicates that the walkingstickLamponius portoricensisRehn forages on a limited array of plant species and selects habitats that contain high densities ofPiper treleaseanumBritton&Wilson. We designed three separate experiments to evaluate (1) if walkingsticks of different ages or of different sex have different food preferences, (2) if previous exposure to only one food type affects subsequent diet composition, and (3) if walkingsticks distinguish among leaves of different quality from the same plant. Four plants [Dendropanax arboreus(L.) Decne&Planch,Piper hispidumSw.,P. treleaseanum, andUrera baccifera(L.) Gaud.] known to be forage for this insect were used in food choice experiments. Multivariate analyses revealed that, at different ages, males and females exhibit different patterns of consumption. Likewise, preexposure to only one food influences subsequent diet differently depending upon preexposure regime and sex. In addition, preferences are shown for different qualities of leaves within single forage species. In particular, lower (older) leaves ofP. treleaseanumare preferred, whereas leaves ofD. arboreusandU. bacciferaare eaten indiscriminately. These results are consistent with the contention that herbivores forage within nutritional constraints. In addition, walkingsticks distinguish between plant species, recognize differences in leaf quality associated with age or position, and modify their diet to reflect past experience.