Beetles are the most diverse group of life on Earth. However numerous organizational problems remain in describing such a large radiation of life. Small, cryptic, drably colored beetles feeding on rotting organic material are prone to such problems. Two such groups are Cucujoidea and Coccinelloidea. Many members are less than 6 mm long, fungus feeding, and difficult to identify with morphology. To address these issues, I conduct six different projects within these superfamilies addressing basic and higher level questions. First, I use molecular phylogenetic analysis to examine the family and subfamily-level relationships within the "flat bark beetle"? lineage. My results demonstrate independent origins of the "flat bark beetle"? body type and support the placement of Propalticidae within Laemophloeidae. Second, using traditional morphological methods, I discover a newly adventive species, Antibothrus morimotoi (Coleoptera: Bothrideridae) that has become established in the United States and provide identification tools. Third, I address the lack of taxonomic resources for identifying Monotomidae (Coleoptera: Cucujoidea) in the New World by building an interactive identification key and information-rich website, creating a hub for future research into this family. Fourth, I provide the first records of the family Monotomidae in Peru, laying the groundwork for future study of that family in that region. One subfamily, three tribes, three genera, and four species are recorded for the first time. Fifth, I examine the lack of biodiversity knowledge about saproxylic beetle in the southeastern United States by collecting and identifying monotomid beetles in the state of Georgia. With limited resources and funding, I expand the number of species of Monotomidae in Georgia by over 100%, which speaks volumes to the current state of biodiversity knowledge in "well-studied"? areas. Finally, I revise the genus Bactridium LeConte 1861 for North America north of Mexico, which is plagued by numerous nomenclatural and taxonomic problems. This revision results in one new species, two new generic names, 31 new combinations, and six synonymies. The genus is identifiable without comparison to type material for the first time in over 100 years.