A central focus in applied entomology is the role that habitat diversity plays in the creation and maintenance of arthropod diversity. Researchers are increasingly exploring the possibility that degraded landscapes such as mixed-used agricultural areas and rainforest fragments might be used to supplement conservation strategies aimed at increasing arthropod biodiversity. Here we present the results of a comparative biodiversity field study in the Puriscal region on the Pacific slope of Costa Rica in a rural community characterized by a mixture of secondary forest and farmland. The study compares beetle and spider diversity among farmland, nearby tropical forest fragments, and weedy “edge” habitats. Diversity of families of Coleoptera and Araneae pitfall catches were compared in each of these three habitats, and quantitative similarity indices across habitats were calculated for the collected specimens. Diversity among the three habitats was similar for beetles, but spiders were more diverse in forest fragments than in edge habitats. Furthermore, composition of beetle families was markedly different across all three habitats; spider families were similar only between forest fragment and edge habitats. We discuss the implications of these findings, and suggest further studies needed to address mechanisms underlying these patterns.